Methods of manufacturing magnetically-responsive optically-variable particles

Abstract

The present disclosure provides, in part, methods for manufacturing magnetically-responsive optically-variable (e.g., magnetochromic) particles, and magnetochromic particle formulations and compositions thereof, and kits comprising one or more components to perform the methods.

Description

METHODS OF MANUFACTURING MAGNETICALLY-RESPONSIVE OPTICALLY-VARIABLEPARTICLESFIELD

[0001] The present disclosure relates, in part, to methods of manufacturing magnetically-responsive particles and particle-based compositions that change optical properties in response to magnetic force.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 608,722, filed December 11 , 2023, the entire contents of which are incorporated by reference herein.BACKGROUND

[0003] Property-changing materials, such as color-shifting materials, are commercially available for a wide variety of applications from smart windows to tattoos, to freshness testing on perishable foods, authentication, brand security, product security, biosensors, and countless others. Invariably, a stimulus is required to initiate a change in color, which can be reversible or irreversible depending on the design of the materials and the intended use. Stimuli for the change in color include temperature, light, electric fields, magnetic fields, a chemical or biochemical entity (e.g. a class of molecules such as a sugar, or a specific molecule such as benzoic acid), and pressure, to name a few. Many of these stimuli have limitations. Specifically, effecting a color change requires ancillary devices or instrumentation (e.g., a magnet or means of creating a magnetic field, a heating element), or stimuli that may not be present in all circumstances (e.g. heat in a cold environment, UV light in a below-ground space). There remains a need for methods to a reversible, color-shifting material that responds to stimuli or actuation in a wider range of environments, at all temperatures and humidities, in all spaces indoor and outdoor, at all altitudes, and at all pressures.SUMMARY

[0004] Accordingly, the present disclosure provides, in part, methods of manufacturing one or more magnetically-responsive optically-variable particle, the method comprising providing a magnetic material, providing one or more particles, attaching the magnetic material to the one or more particles to generate one or more magnetically-responsive particles, applying a first magnetic field to the one or more particles to separate the one or more magnetically-responsive particles from the one or more particles that did not attach magnetic material, disposing the one or more magnetically-responsive particles onto a surface to generate a 2-dimensional array of the one or more magnetically-responsive particles, applying a second magnetic fieldto the one or more magnetically-responsive particles to orient the one or more magnetically-responsive particles on the surface such that an equivalent portion of the surface area of each of the one or more magnetically-responsive particles is exposed relative to one another within the 2-dimensional array, and coating at least a portion of the exposed surface area of the one or more magnetically-responsive particles with at least a first optically active agent to generate one or more magnetically-responsive optically-variable particles.

[0005] In embodiments, providing the one or more particles comprises generating the one or more particles. In embodiments, generating the particles comprises performing one or more of evaporation, chemical or physical self-assembly, droplet-based microfluidics, polymerization (e.g., thermal treatment, UV polymerization, microwave treatment, induction hardening), adsorption, coacervation, mixing, and extrusion. In embodiments, generating the particles comprises droplet-based microfluidics, applying a magnetic field, and / or thermal treatment (e.g., UV polymerization, microwave treatment, induction hardening, etc.).

[0006] In embodiments, generating the particles comprising forming Janus particles (e.g., using various methods for generating magnetic Janus particles, including microfluidics).

[0007] In embodiments, attaching further comprises a click-chemistry reaction to adhere the magnetic material to the one or more particles. In embodiments, the click-chemistry reaction comprises one or more of azide-alkyne cycloaddition, thiol-click reaction (thiol-ene, thiol-yne, thiol-isocyante), Diels-Alder reaction, nitrile oxide cycloaddition, tetrazole cycloaddition, oxime formation, and 1,3-dipolar azide-alkyne cycloaddition (CuAAC).

[0008] In embodiments, attaching further comprises microfluidics to adhere the magnetic material to the one or more particles.

[0009] In embodiments, the one or more particles and / or one or more magnetically-responsive particles and / or one or more magnetically-responsive optically-variable particles comprises a dimension of about or at least about 10 nm, about or at least 20 nm, about or at least about 30 nm, about or at least about 40 nm, about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm, about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or atleast about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm, about or at least about 2 m, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm, about or at least about 200 pm, about or at least about 300 pm, about or at least about 400 pm, about or at least about 500 pm, or about or at least about 1000 pm.

[0010] In embodiments, the magnetic material comprises one or more of magnetic beads and magnetic particles. In embodiments, the magnetic beads and magnetic particles are smaller in dimension than the one or more particles. In embodiments, the magnetic material is ferromagnetic, ferrimagnetic, antiferromagnetic, diamagnetic, paramagnetic, superparamagnetic, and / or antiferromagnetic. In embodiments, the magnetic material comprises one or more of an inorganic, organic, carbon-based, or biomolecule-based magnetic material.

[0011] In embodiments, the magnetic material comprises one or more of iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), manganese (Mn), chromium (Cr), samarium (Sm), alloys or oxides thereof; alloys, intermetallic, and / or oxides of Fe, Co, Ni, Zn, Mn, Sm; oxides are of iron, Fe2O3, FeO, and / or Fe3O4; ferrite material and / or doped materials of Co, Ni, Zn, and / or Mn:FexOy, and / or magnetitetetracyanoethylene (TCNE) salts, [Fe(C5Me5)2]-HTCNE]’-, Li[TCNE], [MnllTPP]|TCNE]« (TPP = tetraphenylporphyrin), [Fell(TCNE)(NCMe)2][FelllCl4], Mnll(TCNE)l(OH2), Mnll(TCNE)[C4(CN)8]i / 2, Fe(TCNE)[C4(CN)8]i / 2, Mnll(TCNE)3 / 2(l3)i / 2, VII[TCNE]X(x « 2), C?H5CIN3Se4, magnetic organic polymers, and polymer-bonded magnets. In embodiments, the magnetic material comprises magnetic iron oxide nanoparticles embedded in polyethylene glycol) diacrylate.

[0012] In embodiments, attaching the magnetic material is performed in a 1 :1 stoichiometric ratio and each particle comprises magnetic material at substantially one location.

[0013] In embodiments, disposing the one or more magnetically-responsive particles onto the surface comprises spraying, evaporating, or blotting the particles onto the surface. In embodiments, the surface comprises a substrate composed of one or more of thin film, plastic, polymer, paper, glass, sapphire, diamond, silicon, organic polymer, organic material, biological polymer, metal oxide, quartz, plastic, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers (TPE), acrylonitrile butadiene styrene (ABS), epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer (COC) cyclic olefin polymer (COP), poly dimethyl siloxane (PDMS), poly ether ester ketone (PEEK), polyetherimide (ULTEM), and nylon.

[0014] In embodiments, the surface comprises one or more detents, indentations, or markers, which enable the one or more magnetically-responsive particles to be disposed in the 2-dimensional array.

[0015] In embodiments, coating comprises spraying, sputtering, painting, glow discharging, or otherwise applying at least one optically active agent onto at least a portion of the external surface area of the one or more magnetically-responsive particles.

[0016] In embodiments, methods herein include applying a third magnetic field to the one or more magnetically-responsive optically-variable particles to re-orient the one or more magnetically-responsive optically-variable particles such that a different portion of the surface area of each is expose, and coating at least a portion of the different portion of the surface area with at least a second optically active agent.

[0017] In embodiments, the one or more magnetically-responsive optically-variable particles are reoriented substantially 180° such that an opposite surface is exposed. In embodiments, the second optically active agent is distinct from the first optically active agent.

[0018] In embodiments, methods herein include encapsulating the magnetically-responsive particles in an outer shell. In embodiments, the magnetically-responsive particles in an outer shell comprises performing one or more of interfacial polymerization, in situ polymerization, coacervation, layer-by-layer growth, adsorption, sol-gel encapsulation, suspension crosslinking, lyophilization, spay drying, co-extrusion, fluidized bed spray coating, and phase inversion precipitation.

[0019] In embodiments, the outer shell is optically transparent to at least a portion of electromagnetic radiation between frequencies of about 10 nm to about 10 cm. In embodiments, the outer shell comprises one or more materials. In embodiments, the outer shell comprises one or more layers. In embodiments, the outer shell comprises at least a portion that is opaque. In embodiments, the outer shell comprises a single, uniform thickness and / or varying thicknesses.

[0020] In embodiments, the outer shell is configured to filter or select for a wavelength or ranges of wavelengths of radiation. In embodiments, the outer shell is configured to transmit a percentage of electromagnetic radiation of about or at least about 100%, about or at least about 99%, about or at least about 98%, about or at least about 97%, about or at least about 96%, about or at least about 95%, about or at least about 94%, about or at least about 93%, about or at least about 92%, about or at least about 91 %,about or at least about 90%, about or at least about 85%, about or at least about 80%, about or at least about 75%, about or at least about 70%, about or at least about 65%, about or at least about 60%, about or at least about 55%, about or at least about 50%, about or at least about 40%, about or at least about 30%, about or at least about 20%, about or at least about 10%, about or at least about 5%, about or at least about 4%, about or at least about 3%, about or at least about 2%, about or at least about 1%, about or at least about 0.5%, about or at least about 0.4%, about or at least about 0.3%, about or at least about 0.2%, about or at least about 0.1 %, about or at least about 0.05%, about or at least about 0.04%, about or at least about 0.03%, about or at least about 0.02%, about or at least about 0.01 %, about or at least about 0.005%, or about or at least about 0.001 %, relative to the intensity or amount of electromagnetic radiation that impinges on the outer shell.

[0021] In embodiments, the outer shell comprises one or more inorganic materials. In embodiments, the one or more inorganic materials comprise one or more of alumina, silica, titania, silicon nitride, zirconia, copper oxide, iron oxide, cobalt oxide, silver, gold, aluminum, copper, tin oxide, nickel oxide, lead oxide, glass, quartz, sapphire, inorganic glasses, diamond, diamond-like materials, zinc oxide, and manganese oxide.

[0022] In embodiments, the outer shell is porous and / or discontinuous. In embodiments, the pores and / or discontinuities comprise about or up to about 0.1%, about or up to about 1%, about or up to about 10%, or about or up to about 50% or more of a total surface area of the outer shell.

[0023] In embodiments, the outer shell fully encapsulates the one or more magnetically-responsive optically-variable particles, resulting in a bounded internal volume.

[0024] In embodiments, the method includes filling the bounded internal volume with one or more of a gas, liquid, polymer, semisolid, and solid material. In embodiments, the gas is atmospheric air. In embodiments, the liquid comprises an aqueous liquid, organic liquid, a mixed aqueous-organic mixture, a polymer, and / or a gel. In embodiments, liquid comprises one or more additives, preservatives, anti-oxidants, lubricants, emulsifiers, stabilizers, thickeners, anti-foaming agents, humectants, anti-bacterial agents, anticaking agents, inorganic salts, pH adjusters, pH buffers, and rheology modifiers. In embodiments, the lubricant comprises one or more of mineral oil, synthetic oil, grease, a silicone-based lubricant, a graphitebased lubricant, molybdenum disulfide, vegetable oils, and Teflon-based lubricants.

[0025] In embodiments, the one or more gas, liquid, polymer, semisolid, and solid material occupies about or up to about 100%, about or up to about 99%, about or up to about 97%, about or up to about 96%,about or up to about 95%, about or up to about 94%, about or up to about 93%, about or up to about 92% about or up to about 91 % about or up to about 90%, about or up to about 85%, about or up to about 80%, about or up to about 70%, about or up to about 60%, about or up to about 50%, about or up to about 40%, about or up to about 30%, about or up to about 20%, about or up to about 15%, about or up to about 10%, about or up to about 9%, about or up to about 8%, about or up to about 7%, about or up to about 6%, about or up to about 5%, about or up to about 4%, about or up to about 3%, about or up to about 2%, about or up to about 1 %, about or up to about 0.5%, about or up to about 0.2%, about or up to about 0.1 %, about or up to about 0.01%, or about or up to about 0.001 % of the bounded internal volume outside of the one or more core particles.

[0026] In embodiments, the outer shell comprises a dimension of about or at least 10 nm, about or at least 20 nm, about or at least about 30 nm, about or at least about 40 nm, about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm, about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or at least about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm, about or at least about 2 pm, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm, about or at least about 200 pm, about or at least about 300 pm, about or at least about 400 pm, about or at least about 500 pm, or about or at least about 1000 pm.

[0027] In embodiments, the one or more particles and / or the outer shell comprises one or more material of plastic, acrylic resin, styrene acrylic copolymer, vinyl acetate ethylene copolymer, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyurethane, epoxy resin, alkyd resin, cellulose acetate, silicone resin, a fluoropolymer resin, chlorinated rubber, a copolymer derived from maleic anhydride, ethylene vinyl acetate, polyethylene, polypropylene, polyamides (nylons), polyester resins, polybutadienes, thermally responsive polymers, latex, hydrocarbons, crude oil derivatives and / or petroleum derivatives, poloxamers, styrenebutadiene block copolymers, polymethylmethacrylate, polybutylmethacrylate, poly(tert-butyl acrylate)-poly(3- (triethoxysilyl)propyl methacrylate) (PtBA-PTPM), polystyrene latex polymer, carboxylated latex polymer,aminated latex polymer, colored polystyrene polymer (dye-infused and / or pigment-infused), colored polystyrene-based carboxylated latex polymer (dye-infused and / or pigment-infused), fluorescent polystyrene-based polymers, fluorescent polystyrene-based carboxylated latex polymers, fluorescent aminated polystyrene-based polymer, surfactant-free polystyrene, carboxylated surfactant-free polymer, polymethyl methacrylate (PMMA) latex polymer, and / or divinylbenzene-crosslinked polystyrene latex, plasticized polyvinyl chloride, plasticized nylon, plasticized polyethylene terephthalate, polyacrylonitrile, polychlorotrifluoroethylene, poly-4, 4'-isopropylidenediphenylene carbonate, polyethylene vinyl ester, polyvinyl chloride-diethyl fumarate, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers, acrylonitrile butadiene styrene, epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer, cyclic olefin polymer, poly dimethyl siloxane, poly ether ester ketone, polyetherimide, metal, metal oxide, metal nitride, inorganic material, silica, organic material, organic polymer, inorganic polymer, biological polymer, synthetic polymer, and combinations thereof.

[0028] In embodiments, the one or more particles and / or the outer shell comprises one or more material of a naturally occurring polymer and / or biological polymer comprising a nucleic acid (DNA, RNA), amino acid (peptide, protein), polysaccharide, or lipid.

[0029] In embodiments, the optically active agents (e.g., at least the first optically active agent and / or at least the second optically active agent) possesses an extinction in the electromagnetic spectrum between the x-ray / ultraviolet region (wavelengths >10 nm) and microwave / radio region (<10 cm).

[0030] In embodiments, at least the first optically active agent and / or at least the second optically active agent exhibits a color in the visible electromagnetic spectrum and / or comprising an extinction, reflection, or scattering at a wavelength from about or at least about 300 nm to about or at least about 1200 nm. In embodiments, at least the first optically active agent and / or at least the second optically active agent comprises a color of one or more of white, black, red, orange, yellow, green, blue, indigo, violet, and variations of hue, shade, and intensity therebetween.

[0031] In embodiments, the one or more magnetically-responsive optically-variable particles comprises two optically active agents, three optically active agents, four optically active agents, or five or more optically active agents.

[0032] In embodiments, at least the first optically active agent and / or at least the second optically active agent comprises a dye. In embodiments, the dye comprises one or more of Rhodamine B, Congo Red,Crystal Violet, Methylene Blue, Acridine Orange, Nile Red, Malachite Green, Eosin Y, Cresol Red, Fluorescein, and Indigo.

[0033] In embodiments, at least the first optically active agent and / or at least the second optically active agent comprises a pigment. In embodiments, the pigment comprises a water-soluble pigment. In embodiments, the water-soluble pigment comprises one or more of anthocyanin, anthraquinone, carotenoid, violacein, melanin, pyocyanin, prodiginines, asperversin, benzoquinone, anthraquinone, and derivatives thereof.

[0034] In embodiments, the pigment comprises one or more of Titanium White (PW6), Zinc White (PW4), Carbon Black (PBk7), Mars Black (P Bk11 ), Iron Oxide Red (PR101 ), Cadmium Red (PR108), Alizarin Crimson (PR83), Cadmium Orange (PO20), Cadmium Yellow (PY35), Lemon Yellow (PY3), Chromium Green Oxide (PG17), Phthalo Green (PG7), Ultramarine Blue (PB29), Cobalt Blue (PB28), Cerulean Blue (PB35), Prussian Blue (PB27), Burnt Sienna (PBr7), Raw Umber (PBr7), Raw Sienna (PBr7), and Yellow Ochre (PY43).

[0035] In embodiments, the pigment is an organic pigment or an inorganic pigment.

[0036] In embodiments, the organic pigment or inorganic pigment is a white pigment. In embodiments, white pigment is one or more of lead white (2PbCO3'Pb(OH)2), kaolin, silica (SiCk), titanium dioxide (TiCWrutile and anatase), zinc oxide (ZnO), zinc sulfide (ZnS), and lithopone (ZnS + BaSO4).

[0037] In embodiments, the organic pigment or inorganic pigment is a black pigment. In embodiments, the black pigment is one or more of coal (charcoal), groutite (a-MnOOH), manganite (y-MnOOH), hausmannite (MnsCk), carbon black, iron oxide black (FeaCk), and spinel black (CuCr2O4).

[0038] In embodiments, the organic pigment or inorganic pigment is a colored pigment.

[0039] In embodiments, the colored pigment comprises a yellow pigment. In embodiments, the yellow pigment comprises one or more of yellow ochre (a-FeOOH), auric pigment (AS2S3), lead ochre (PbO), lead tin yellow (Pb2SnO4, PbSn2SiO / ), Naples yellow (Pb(SbC>3)2), zinc yellow (ZnaCrCh), Indian yellow (C19H16O10), iron oxide yellow (a-FeOOH), chromium titanium yellow ((Ti,Cr,Sb)C>2), nickel titanium yellow ((Ti, Ni,Sb)O2), lead yellow (PbCrCU), cadmium yellow (CdS), and bismuth yellow (BiVO4).

[0040] In embodiments, the colored pigment comprises a red pigment. In embodiments, the red pigment comprises one or more of red ocher (a-Fe2O3), Terra di Siena (a-Fe2O3), vermilion (HgS), lead red (PbaCu),alizarin madder varnish, alizarin red (C14H8O4), iron oxide red (o-Fe2O3), molybdate red (Pb(Cr,S,Mo)O4), and cadmium red (Cd(S,Se)).

[0041] In embodiments, the colored pigment comprises a green pigment. In embodiments, the green pigment comprises one or more of green earth (Fe silicates), Schweinfurt green (C4H6AS6CU4O16), chromium oxide green (C Os), chromium oxide hydrate green (CrOOH), and cobalt green (CtoTiCk).

[0042] In embodiments, the colored pigment comprises a blue pigment. In embodiments, the blue pigment comprises one or more of lazurite (lapis lazuli), Egyptian blue (CaCuSi40io), azurite (2CUCO3'CU(OH)2), malachite (CuCO3'Cu(OH)2), cobalt blue (COAI2O4), Cobalt blue (COAI2O4), ultramarine blue: (Na6Al6Si6O24(NaSn)), and iron blue (K[FelllFell(CN)6] xH2O).

[0043] In embodiments, the colored pigment comprises a brown pigment. In embodiments, the brown pigment comprises one or more of burnt umber (Fe2C>3-xMnO2), brown ocher (a-Fe2C>3 + Mn oxides), and limonite (mixture of different Fe oxides).

[0044] In embodiments, the pigment is one or more of an oxide or oxide hydroxide pigment (TiO2, ZnO, a-Fe2O3, a-FeOOH, y-Fe2O3, FesCk, Cr2O3, CrOOH, PbO, PB3O4, MnsO4, -MnOOH, Sb2O3), a complex oxide pigment (COAI2O4, CuCr2O4, Co2TiO4, (Ti,Ni,Sb)O2, (Ti,Cr,Sb)O2), a carbonate hydroxide pigment (2PbCO3-Pb(OH)2, 2CUCO3-CU(OH)2, CUCO3-CU(OH)2), a sulfide / selenide pigment (ZnS, CdS, Cd(S,Se), CdSe, y-Ce2S3, HgS, AS2S3), a chromate / molybdate pigment (PbCrO4, Pb(Cr,S)O4, Pb(Cr,S,Mo)O4, ZnCrO4, BaCrO4, SrCrO4), a vanadate pigment (BiVO4, 4BiVO4-3Bi2MoOe), a stannate pigment (Pb2SnO4, PbSn2SiO / , Co2SnO4, CoSnOs), a phosphate pigment (Co3(PO4)2), an antimonate pigment (Pb(SbO3)2), an arsenate pigment (Cu(AsO3)2), an ultramarine pigment (NaeAl6Si6O24(NaSn)), a hexacyanidoferrate / hexacyanoferrate pigment (K[FelllFell(CN)6] xH2O (x = 14-16)), an oxonitride pigment (CaTaO2N, LaTaON2), an elemental-based pigment (C, Al, Cu, Cu / Zn, Au), a spinel-based pigment, and a rutile-based metal pigment.

[0045] In embodiments, the inorganic pigment is one or more of a transparent effect pigment, goniochromatic pigments, pearlescent pigment, metallic pigment, interference pigment, metallic effect pigment, fluorescent pigment, luminescent pigment, phosphorescent pigment, magnetic pigment, and anticorrosive pigment.

[0046] In embodiments, the metallic pigment comprises one or more of aluminum, bronze, and copper metallic pigment. In embodiments, the pearlescent pigment comprises one or more of mica, titanium dioxide,and bismuth oxychloride. In embodiments, the fluorescent pigment comprises one or more fluorescent dye and pigment comprising a fluorescent mineral.

[0047] In embodiments, the phosphorescent pigment comprises zinc sulfide and / or strontium aluminate. In embodiments, the interference pigment comprises titanium dioxide-coated mica and / or aluminum oxidecoated mica.

[0048] In embodiments, at least the first optically active agent and / or at least the second optically active agent comprises an anisotropic particle. In embodiments, the anisotropic particle comprises a nanoparticle of the one or more metals, optionally comprising a nanorod of one or more of chromium (Cr), gold (Au), silver (Au), and aluminum (Al).

[0049] In embodiments, the optically active agent comprised a plasmonic material. In embodiments, the plasmonic material comprises a pigment, particle, foil, and / or film. In embodiments, the plasmonic material comprises a polymer-film loaded with noble metal nanoparticles.

[0050] In embodiments, the goniochromatic pigment comprises aluminum coated with magnesium fluoride embedded in chromium.

[0051] In embodiments, the method includes coating the one or more magnetically-responsive optically- variable particles with one or more coating materials. In embodiments, the one or more coating materials comprises one or more organic substance, inorganic substance, biological substance, and combinations thereof. In embodiments, the one or more coating materials comprises one or more of a lubricant, surface treatment, and polishing agent. In embodiments, the one or more lubricant, surface treatment, and polishing agent comprises one or more of polytetrafluoroethylene (PTFE), hydroxylated self-assembled monolayers, vitreous enamel, ceria (cerium oxide), ceramics, anodized metals, and silica.

[0052] In embodiments, the method comprises formulating the one or more magnetically-responsive optically-variable particles.

[0053] In embodiments, formulating comprises suspending the magnetically-responsive optically- variable particles in a liquid. In embodiments, the liquid comprises one or more of an emulsifier, surfactant, solvent, viscosity modifier, salt, rheological agent, anti-microbial agent, pH adjuster, buffer, suspending agent, biological polymer, synthetic polymer, and organic molecule. In embodiments, the one or more magnetically-responsive optically-variable particles are present in a concentration of about or less than about 0.001% (w / v), about or less than about 0.1% (w / v), about or less than about 0.5% (w / v), about or less thanabout 1 % (w / v), about or less than about 2% (w / v), about or less than about 3% (w / v), about or less than about 4% (w / v), about or less than about 5% (w / v), about or less than about 6% (w / v), about or less than about 7% (w / v), about or less than about 8% (w / v), about or less than about 9% (w / v), about or less than about 10% (w / v), about or less than about 12% (w / v), about or less than about 14% (w / v), about or less than about 16% (w / v), about or less than about 18% (w / v), about or less than about 20% (w / v), about or less than about 25% (w / v), about or less than about 30% (w / v), about or less than about 35% (w / v), about or less than about 40% (w / v), about or less than about 50% (w / v), about or less than about 60% (w / v), or about or less than about 70% (w / v).

[0054] In embodiments, formulating the one or more magnetically-responsive optically-variable particles comprises arranging into an array on a substrate. In embodiments, the substrate comprises a foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material. In embodiments, the one or more magnetically-responsive optically-variable particles cover a surface area of about or less than about 1 %, about or less than about 5%, about or less than about 10%, about or less than about 15%, about or less than about 20%, about or less than about 25%, about or less than about 30%, about or less than about 35%, about or less than about 40%, about or less than about 45%, about or less than about 50%, about or less than about 55%, about or less than about 60%, about or less than about 65%, about or less than about 70%, about or less than about 75%, about or less than about 80%, about or less than about 85%, about or less than about 90%, about or less than about 95%, or about or less than about 99%.

[0055] In embodiments, at least a portion of the substrate is transparent to at least a portion of the visible electromagnetic (EM) spectrum and / or opaque. In embodiments, the substrate comprises a material of one or more of glass, sapphire, diamond, silicon, organic polymers, organic materials, biological polymers, metal oxides, quartz, plastic, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers (TPE), acrylonitrile butadiene styrene (ABS), epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer (COC) cyclic olefin polymer (COP), poly dimethyl siloxane (PDMS), poly ether ester ketone (PEEK), polyetherimide (ULTEM) and nylon.

[0056] In embodiments, formulating the one or more magnetically-responsive optically-variable particles comprises assembling the one or more magnetically-responsive optically-variable particles into a fiber, thread, yarn, twine, and / or material thereof.

[0057] In aspects, described herein is a microfl uidics-based method of manufacturing magnetically- responsive optically-variable particles comprising generating one or more Janus particles in a microfluidicchannel, wherein the Janus particle is composed of at least one magnetic material, applying a magnetic field to the microfluidic channel to induce anisotropy in the one or more Janus particles, and curing the one or more Janus particles in the magnetic field using a thermal treatment to generate one or more magnetically- responsive particles optically-variable particles. In embodiments, the Janus particles are generated using two or more materials, optionally wherein the materials are thermally responsive polymers, and further optionally wherein the two or more materials have distinct optical properties. In embodiments, the microfluidic channel comprises an elongated portion of the channel which alters the shape of the Janus particles that are generated (e.g., to generate elongated particles). In embodiments, the induced anisotropy comprises orienting the magnetic material to one portion of the one or more Janus particles to generate a magnetic dipole. In embodiments, the thermal treatment comprises one or more of microwave treatment ultraviolet (UV) polymerization, and induction.

[0058] In embodiments, the method comprises disposing the one or more magnetically-responsive optically-variable particles onto a surface to generate a 2-dimensional monolayer or array of the one or more magnetically-responsive optically-variable particles. In embodiments, the method comprises applying a second magnetic field to the one or more magnetically-responsive particles to orient the one or more magnetically-responsive particles on the surface such that an equivalent portion of the surface area of each of the one or more magnetically-responsive particles is exposed relative to one another within the 2- dimensional monolayer or array. In embodiments, the method comprising coating at least a portion of the exposed surface area of the one or more magnetically-responsive optically-variable particles with at least one optically active agent. In embodiments, the method comprises encapsulating the magnetically- responsive optically-variable particles in a shell.

[0059] In aspects, described herein are compositions comprising one or more magnetically-responsive optically-variable (e.g., magnetochromic) particles produced by the methods described herein.

[0060] In aspects, described herein are kits comprising components useful for performing one or more steps of the methods described herein. In embodiments, the kit comprises one or more magnetically- responsive particles and one or more optically active agents. In embodiments, the kit comprises a means for applying a magnetic field and / or a substrate to dispose the one or more magnetically-responsive particles upon. In embodiments, the kit comprises one or more of magnetic material, one or more particles, a means for applying a magnetic field (e.g., as magnet), a substrate to dispose the particles upon, and at least one optically active agent.DESCRIPTION OF THE DRAWINGS

[0061] Figs. 1A-1 B depict illustrative, non-limiting diagrammatic side-view representations of exemplary encapsulated, magnetochromic yolk-shell (EMYS) particles. Fig. 1A depicts a yolk particle comprising (i) a first optically active agent, (ii) a second optically active agent, and (iii) a surface-associated magnetic material, where the yolk particle is contained within an encapsulant (shell). Fig. 1 B depicts a yolk particle comprising i) a first optically active agent, (ii) a second optically active agent, and (iii) a surface- associated magnetic material, where the yolk particle is contained within a porous encapsulant (shell).

[0062] Figs. 2A-2B depict illustrative, non-limiting diagrammatic side-view representations of exemplary encapsulated, magnetochromic yolk-shell (EMYS) particles. Fig. 2A depicts an oblate spheroidshaped yolk particle comprising (i) a first colored material, (ii) a second colored material, and (iii) a surface- associated magnetic material, where the yolk particle is contained within an encapsulant. Fig. 2B depicts an oblate spheroid-shaped yolk particle comprising (i) a first colored material, (ii) a second colored material, and (iii) an oblate spheroid-shaped magnetic material, where the yolk particle is contained within an encapsulant.

[0063] Figs. 3A-3E depict an illustrative, non-limiting diagrammatic side view of steps in the synthesis of particles (shown as transparent spheres) harboring one surface-associated magnetic particle (shown as smaller black spheres). Fig. 3A depicts a solution of magnetic material; Fig. 3B depicts a solution of particles. Fig. 3C depicts the combination in solution of the magnetic material and particles, resulting the chemical attachment of the two. Fig. 3D-3E depicts an isolation step where a magnetic field is applied to separate magnetically-responsive particles.

[0064] Fig. 4 depicts an illustrative, non-limiting diagram of methods of manufacturing magnetically- responsive optically-variable particles.

[0065] Figs. 5A-5B depict an illustrative, non-limiting diagrammatic side-view representations of exemplary roll-to-roll particle coating by automated Langmuir-Blodgett assembly and deposition and resulting particles made by such processes. Fig. 5A depicts the main components of the process. Fig. 5B depicts an exemplary spherical particle comprising a non-magnetic material (shown as white) onto which a hemispherical coating of magnetic material has been deposited (shown as gray).

[0066] Figs. 6A-6B depict an illustrative, non-limiting diagrammatic side-view representations of an exemplary microfluidic apparatus for synthesis of anisotropic, magnetic polymer Janus particles and an image of representative particles. Fig. 6A depicts the principal hardware, fluid, and particle components ofthe process. Fig. 6B depicts an optical microscopic image of approximately 50-micron diameter polymeric particles made using the apparatus of Fig. 6A.

[0067] Figs. 7A-7D depict illustrative, non-limiting diagrammatic representations of a group of cylindrically-shaped, rod-shaped, oblate spheroid-shaped, and other anisotropic magnetic Janus microparticles made using microfluidics. Fig. 7A depicts microscopic images of particles. Fig. 7B depicts magnetic material on the outer surface of the particle. Fig. 7C depicts the magnetic material contained within the particle. Fig. 7D depicts magnetic Janus particles in which there are (i) two spatially distinct magnetic materials; (ii) a continuous phase of magnetic materials confined to a band; (iii) a dimer of spherical particles, with each particle having magnetic material; (iv) partially merged dimer of spherical particles; (v) a rod-shaped particle with a continuous phase of magnetic materials; and (vi) magnetic material is associated with a single colored material.

[0068] Figs. 8A-8H depict illustrative, non-limiting diagrammatic representations of a series of steps of methods herein. Fig. 8A depicts a particle in the shape of an oblate spheroid (e.g., magnetic Janus particles that comprise a core like that of Fig. 2A). Fig. 8B depicts the particles of Fig. 8A in a fluid suspension. Fig. 8C depicts a substrate containing a 2-D array of features (ellipses) designed to fit one particle of Fig. 8A per feature. Fig. 8D depicts a 2-D array assembly of the particles on the substrate. Fig. 8E depicts attachment of magnetic material (e.g., a magnetic particle) to each particle in the array. Fig. 8F depicts the application of a magnetic field to orient the particles in the array such that the magnetic particles are all facing the magnet and the particles are each in the same orientation relative to the magnetic field. Fig. 8G depicts deposition of a colored material (e.g., shown as gray) onto the surface of the particles of Fig. 8F. Fig. 8H depicts a representative particle of Fig. 8G after release from the substrate having a magnetic element and at least two distinct optical properties.

[0069] Figs. 9A-9E depict illustrative, non-limiting diagrammatic representations of a series of steps of methods herein. Fig. 9A depicts magnetic Janus particles suspended in solution. Fig. 9B depicts the particles of Fig. 9A assembled into a 2-dimensional (2-D) array on a planar substrate containing features (circular pores) designed to fit a single particle each. Fig. 9C depicts the use of a magnet to orient the particles such that all magnetic materials are facing the magnet. Fig. 9D depicts deposition of a colored material (e.g., shown as gray) onto the surface of the 2-D array in Fig. 9C. Fig. 9E depicts the particles of Fig. 9D formulated into solution.

[0070] Figs. 10A-10E depict illustrative, non-limiting diagrammatic representations of a series steps of methods herein. Fig. 10A depicts a magnetically-responsive particle substantially corresponding to the spherical particle of Fig. 1A suspended in solution; for simplicity, Fig. 10B depicts one such particle. Fig. 10C depicts the particle of Fig. 10B with one or more coating materials. Fig. 10D depicts the coated particle of Fig. 10C encapsulated in a shell. Fig. 10E depicts the particle of Fig. 10D with one or more of the coating materials removed.

[0071] Figs. 11A-11C depict illustrative, non-limiting diagrammatic representations of the operation of a collection of encapsulated, magnetochromic yolk-shell particles of the present disclosure. Fig. 11 A depicts a side-on view of a two-dimensional array of particles, with all the magnetically-responsive particles are in the same orientation (e.g., such that the magnetic materials are all facing to the left). The shell of each particles is immobile, and is directly associated with a substrate (e.g., shown as the grey plane in contact at the bottom of each particle). An observer looking down at this particle array would observe the color associated with the top hemisphere of each magnetically-responsive particle (e.g., the top-facing white hemisphere). Fig. 11 B depicts the array after a magnetic field is applied, oriented from left to right, causing the particles to rotate clockwise by 180°. The observer now observes the color associated with the bottom hemisphere (e.g., the cross-hatched hemisphere). Fig. 11 C depicts the array of Fig. 11 B after a magnetic field is applied in the opposite direction, oriented from right to left, causing the particles to rotate counterclockwise by 180°. The observer once again observes the color associated with the top hemisphere.

[0072] Figs. 12A-12E depict illustrative, non-limiting diagrammatic representations of a series of materials and of steps of methods herein. Fig. 12A depicts a spherical, two-colored Janus particle, with the top hemisphere one color (shown as black), and the bottom hemisphere another color (shown as white), and wherein the Janus particle incorporates a material that responds to a magnetic field. Fig. 12B shows the Janus particle of Fig. 12A to which a coating has been applied (shown in gray), and Fig. 12C shows small particles (shown in gray) that may be generated as a result of the coating process. Fig. 12D depicts the particles of Figs. 12B and 12C together in a fluid solution, and Fig.12E shows the use of a magnet to separate the particles of Fig. 12B from those of Fig. 12C.

[0073] Figs. 13A-13E depict illustrative, non-limiting diagrammatic representations of a series of materials and steps of methods herein. Fig. 13A depicts a spherical, two-colored Janus particle, with the top hemisphere one color (shown as black), and the bottom hemisphere another color (shown as white), with a first (inner) coating (shown in gray) and a second (outer) coating (shown in black), and wherein the Janusparticle incorporates a material that responds to a magnetic field. Fig. 13B shows the Janus particle of Fig. 13A in which the inner coating has been removed, and Fig. 13C shows small particles (shown in gray) corresponding to the removed inner coating. Fig. 13D depicts the particles of Figs. 13B and 13C together in a fluid solution, and Fig.13E shows the use of a magnet to separate the particles of Fig. 13B from those of Fig. 13C.

[0074] Figs. 14A-14E depict illustrative, non-limiting diagrammatic representations of a series of materials and steps of methods herein. Fig. 14A depicts an array of magnetically responsive Janus particles, with the top hemisphere (shown as black) comprising a magnetically responsive material, and the bottom hemisphere (shown as white), comprising a magnetically non-responsive material, in which the particles are all oriented such that the black (magnetically responsive) hemisphere of the particles is face up. Fig. 14B depicts the particles of Fig. 14A in which, as the result of response to a moving magnetic field, the particles have changed orientation such that the white hemisphere of the particles is face up. Fig. 14C illustrates four initial positions of a magnet in the plane of the array of particles of Figs. 14A and 14B. Fig. 14D illustrates two initial positions of a magnet above and below the plane of the array of particles of Figs. 14A and 14B. Fig. 14E illustrates directions of movement along the x, y, and z axis that could be used to initiate the particle movement associated with the transition between the particles in Figs. 14A and 14B.

[0075] Fig. 15 depicts a transmission optical microscopy image if magnetic Janus Particles (Fe / Silica) after coating with a swellable methacrylic acid-based polymer with pH-induced swelling.DETAILED DESCRIPTION

[0076] The present disclosure provides, in part, methods of manufacturing magnetically-responsive optically-variable particles, also referred to herein as “particles,” “magnetochromic particles,” “encapsulated magnetochromic yolk-shell (EMYS) particles,” “encapsulated magnetochromic particles,” “magnetic yolkshell particles, and “encapsulated magnetic yolk-shell particles.” In embodiments, also provided herein are formulations and compositions of magnetically-responsive optically-variable particles produced from methods described herein, kits comprising components thereof, and kits for performing one or more steps of methods described herein.

[0077] Magnetically-responsive optically-variable (e.g., magnetochromic) particles comprise a particle of approx. 10 nm to 1 mm in dimension (e.g., diameter, length, width, etc., depending upon geometry) with at least a portion comprised of magnetic material and having at least two optical states such that the magnetochromic particles change optical property relative to an observer as a function of application of amagnetic field. In embodiments, the optical properties of each optical state include, but are not limited to, absorption, scattering, transmission, refraction, reflectance, reflection, transmittance, dispersion, birefringence, polarization, color, hue, tint, albedo, turbidity, fluorescence, luminescence, phosphorescence, Raman scattering, and surface enhanced Raman scattering. In embodiments, methods herein include formulating the magnetochromic particles into a composition (e.g., a fluid, ink, suspension, fiber, film, etc.) to be printed, sprayed, or otherwise imbued onto or into an object to confer the optical properties in response to stimuli applied to the object.

[0078] In embodiments, the magnetochromic particle comprises a particle (e.g., a yolk-shell particle). In embodiments, the yolk-shell particle comprises a singular material, two materials, or more than two materials. In embodiments, the yolk-shell particle comprises at least two materials, each with a distinct density. In embodiments, optically active agents are disposed on the yolk-shell particle, and / or the yolk-shell particle is composed of a material having optical properties, which acts as an optical agent. In embodiments, the magnetochromic particle is encapsulated in an outer shell. In embodiments, the shell is transparent to at least a portion of an electromagnetic spectrum between frequencies of about 10 nm to about 10 cm, and the magnetochromic particle exhibits a change in an optical property as a function of exposure to a force that is observable through the shell.

[0079] For example, in non-limiting embodiments and in reference to Figs. 1A-1 B, a side-view representation of a magnetochromic particle is illustrated. In embodiments, the magnetochromic particle 100 is encapsulated in an outer shell 108; however in some embodiments the magnetochromic particle 100 is not encapsulated. In embodiments, the magnetochromic particle 100 comprises a magnetic material 102, a first optically-active agent 104 and a second optically-active agent 106. In embodiments, at least one of the first- optically active agent 104 and / or second optically-active agent 106 comprises a material the particle is composed of which necessarily has an optical property (e.g., color, scattering, emissivity, reflectance, etc.). In embodiments, the first optically-active agent 104 is a less dense material with a first optical property, and the second optically-active agent 106 is a denser material with a second optical property. In embodiments, the particle 100 (e.g., core particle which has the magnetic material and optically-active agents) is composed of at materials having at least two different densities (e.g., as defined as the mass per unit of volume). In embodiments, the particle 100 (e.g., core particle) is composed of at materials that are anisotropic.

[0080] In embodiments, and in reference to Figs. 1A-1 B, the magnetic material is attached to the particle to be surface-adhered (e.g, as shown in Fig. 1 A), or is embedded within the particle (e.g, as shown in Fig. 1 B).

[0081] In embodiments, the magnetochromic particle has an encapsulant or outer shell that surrounds the inner particle. In embodiments, the magnetochromic particle has a transparent outer shell. In embodiments, “transparent” refers to a property of at least a portion of the outer shell comprising a material that is transparent to (e.g., allows transmission of) at least a portion of the electromagnetic spectrum between the x-ray / ultraviolet region (wavelengths >10 nm) and microwave / radio region (<10 cm). In embodiments, the shell is configured to allow observation of the change in optical property, for example, where the change is a change in color in the electromagnetic spectrum between about 300 nm and about 1200 nm.

[0082] In embodiments, the magnetochromic particle is substantially spherical. In embodiments, the magnetochromic particle has non-spherical shapes, for example, as illustrated in Figs. 2A-2B. In embodiments, and in reference to Fig. 2A, an oblate spheroid-shaped yolk particle is manufactured having (i) a first colored material (e.g, a first optically active agent), (ii) a second colored material (e.g, a second optically active agent), and (iii) a surface-associated magnetic material, where the yolk particle is contained within an encapsulant (shell) and there is a substantial amount of space between the shell and magnetically- responsive particle. In embodiments, and in reference to Fig. 2B, an oblate spheroid-shaped yolk particle is manufactured having (i) a first colored material (e.g, a first optically active agent), (ii) a second colored material (e.g, a second optically active agent), and (iii) a surface-associated magnetic material, where the yolk particle is contained within an encapsulant (shell) and there is little space between the shell and magnetically-responsive particle, where the particle rotates freely in place, e.g, along a single axes or multiple axes.Methods of Manufacturing Magnetically-Responsive Optically-Variable Particles

[0083] In aspects, described herein are methods of manufacturing magnetochromic particles.

[0084] In embodiments, the method comprises providing a magnetic material and providing one or more particles. In embodiments, the magnetic material and / or particles are in the form of a solution, including aqueous solutions, organic solutions, and inorganic solutions, for example, the magnetic material and / or one or more particles are suspended in a water-based buffer or solvent, an organic solvent (e.g, alcohol, etc.) (e.g, as shown in Fig. 3A-3E).

[0085] In embodiments, providing the one or more particles comprises generating the one or more particles. In embodiments, generating the one or more particles includes a number of fabrication techniques used to generate particles on size scales from millimeters through microns down to nanometer dimensions. In embodiments, these methods include in non-limiting examples: chemical or physical methods including but not limited to self-assembly, droplet-based microfluidics, polymerization (ultraviolet polymerization), adsorption, coacervation, mixing, extrusion, and / or manipulation of polymers.

[0086] In embodiments, the method includes solution-deposition, for example, as illustrated in Fig. 4. In embodiments, magnetically-responsive optically-variable (e.g., magnetochromic) particles are manufacturable using a combination of solution-based chemistry and non-solution-based steps. In embodiments, a solution of magnetic material (e.g., magnetic beads / particles at approx. 10 nm to about 100 pm in diameter) and a solution of particles (e.g., Janus particles composed of polymer of approx. 100 nm to about 500 pm in diameter) are admixed to attach the magnetic material to the particles (e.g., as shown in Figs. 3A-3C and Fig. 4). In embodiments, the surfaces of the materials and the contents of the solutions are selected to be conducive to click-chemistry-based attachment. In embodiments, a magnetic field is applied to separate magnetic material-conjugated particles from non-conjugated particles, resulting in purified magnetically-responsive particles (e.g., as shown in Figs. 3D-3E and Fig. 4).

[0087] In embodiments, the magnetically-responsive particles are deposited onto a surface (e.g., using spray deposition, etc.), where the surface is a substrate having detents, indentations, etc., which orient the magnetically-responsive particles in a regularly-spaced 2-D array (e.g., as shown in Fig. 4). In embodiments, a magnetic field is again applied to orient the magnetically-responsive particles such that an equivalent surface area is exposed in each (e.g., as shown in Fig. 4).

[0088] In embodiments, an optically active agent is applied to the exposed surface (e.g., by spray coating, spray painting, evaporation, etc.), where an optional mask is overlaid to customize the coating process. In embodiments, a magnetic field is additionally applied one or more times to re-orient the magnetochromic particles to again coat with one or more additional optical agents.

[0089] In embodiments, and in reference to Figs. 5A-5B, methods herein include a roll-to-roll particle coating method using automated Langmuir-Blodgett assembly and deposition is used to manufacture the magnetically-responsive particles. In embodiments, and in reference to Fig. 5A, the process comprises magnetic particles produced using solution chemistry (e.g., with components in the suspension and carrying liquid), where the particles are transferring in to one or more Langmuir monolayers, which include a rollingsubstrate support in contact with the liquid-gas interface. In embodiments, the rolling substrate contains one or more monolayers of an organic material or inorganic material, which deposits particles from the surface of the liquid, or via immersing (or emersion) into the liquid. In embodiments, the monolayer is adsorbed with particles substantially homogeneously with each immersion or emersion step and forms films with accurate thicknesses. In embodiments, and in reference to Fig. 5B, substantially spherical magnetically-responsive particles (e.g., including various other shapes) produced from this process comprise a non-magnetic material (e.g., shown as white) onto which a hemispherical coating of magnetic material has been deposited (e.g., shown as gray).

[0090] In embodiments, and in reference to Figs. 6A-6B, methods herein include microfluidic processes including an apparatus for synthesis of anisotropic, magnetic polymer Janus particles and an image of representative particles. In embodiments, and in reference to Fig. 6A, the microfluidic apparatus includes one or more inlets (e.g., continuous phase inlet and dispersed phase inlet) which can accommodate a variety of materials for producing particles by disposing droplets into the microfluidic chamber. In embodiments, this process results in anisotropic droplets which are formed of one or more polymers, e.g. a magnetic polymer, etc. In embodiments, a curing step is included, which involves a thermal treatment (e.g., microwave treatment or ultraviolet (UV) treatment) to accelerate polymerization and solidification of the particle materials (e.g., as shown in Fig. 6A). In embodiments, and in reference to Fig. 6B, magnetically-responsive particles produced using microfluidics are observable by optical microscopic image, where exemplary particles as shown are approximately 50 pm diameter polymeric particles.

[0091] Methods herein, in embodiments, include generating one or more Janus particles in a microfluidic channel, wherein the Janus particle is composed of at least one magnetic material, applying a magnetic field to the microfluidic channel to induce anisotropy in the one or more Janus particles, and curing the one or more Janus particles in the magnetic field using a thermal treatment to generate one or more magnetically-responsive particles optically-variable particles. In embodiments, the Janus particles are generated using two or more materials, optionally wherein the materials are thermally responsive polymers, and further optionally wherein the two or more materials have distinct optical properties. In embodiments, the microfluidic channel comprises an elongated portion of the channel which alters the shape of the Janus particles that are generated. In embodiments, the induced anisotropy comprises orienting the magnetic material to one portion of the one or more Janus particles to generate a magnetic dipole. In embodiments, the thermal treatment comprises one or more of microwave treatment, ultraviolet (UV) polymerization, thermal-based curing / hardening, and induction (e.g., induction hardening). In embodiments, the methodfurther comprises disposing the one or more magnetically-responsive optically-variable particles onto a surface (e.g., using a Langmuir blotting method to generate a 2-D monolayer or array of the one or more magnetically-responsive optically-variable particles). In embodiments, the method comprises applying a second magnetic field to the one or more magnetically-responsive particles to orient the one or more magnetically-responsive particles on the surface such that an equivalent portion of the surface area of each of the one or more magnetically-responsive particles is exposed relative to one another within the 2-D monolayer or array. In embodiments, the method comprising coating at least a portion of the exposed surface area of the one or more magnetically-responsive optically-variable particles with at least one optically active agent.Formation of Particles

[0092] In embodiments, chemical techniques such as coacervation are used to generate the particles. Coacervation, in embodiments, is a process in which two or more polymers are mixed together in a solution and undergo phase separation to form two distinct phases. In embodiments, one phase is rich in polymer, while the other phase is depleted in polymer and mostly contains solvent. Coacervation, in embodiments, is used to produce microspheres or microcapsules, which are small, spherical particles that can be used for drug delivery, encapsulation, and other applications. During coacervation, in embodiments, the polymers undergo a process of self-assembly, where they form complex structures through non-covalent interactions such as electrostatic forces, hydrogen bonding, and van der Waals forces. In embodiments, methods of generating the magnetochromic particles includes coacervation to make the starting particle and one or more additional coacervation steps for attaching the magnetic material and / or generating a shell.

[0093] In embodiments, the one or more particles are manufactured using microfluidics, evaporation, deposition, and / or similar methods. In embodiments, the particle comprises two or more optically active agents incorporated into a transparent polymer.

[0094] In embodiments, particles are manufactured using latex polymer particles, for example, using MAGSPHERE (micron-sized latex polymer particle), having approximately 15 pm diameter particle size. In embodiments, particles are manufactured using, in non-limiting examples, one or more of polystyrene latex polymer, carboxylated latex polymer, aminated latex polymer, colored polystyrene polymer (dye-infused and / or pigment-infused), colored polystyrene-based carboxylated latex polymer (dye-infused and / or pigment- infused), fluorescent polystyrene-based polymers, fluorescent polystyrene-based carboxylated latex polymers, fluorescent aminated polystyrene-based polymer, surfactant-free polystyrene, carboxylatedsurfactant-free polymer, polymethyl methacrylate (PMMA) latex polymer, and divinylbenzene (DVB)- crosslinked polystyrene latex polymer.

[0095] In embodiments, generating the particles comprising forming Janus particles. In embodiments, Janus particles are a type of particle characterized by having two distinct regions or "faces" with different physical and / or chemical properties. In embodiments, the two faces of Janus particles can have different surface chemistry, size, shape, or polarity, which makes them useful in a variety of applications, including drug delivery, catalysis, and self-assembly. In embodiments, Janus particles are attractive, because they are a unique class of anisotropic materials that are simple, but for which all the structural parameters can be completely controlled. In embodiments, Janus particle-based magnetochromic particles are synthesized at large scale, and under surfactant-free conditions, for example, as described in WALTHER and MULLER, ‘‘Janus Particles: Synthesis, Self-Assembly, Physical Properties, and Applications,” Chem. Rev., Vol. 113, 2013: pp. 5194-5261; VOGEL etal. “Advances in Colloidal Assembly: The Design of Structure and Hierarchy in Two and Three Dimensions,” Chem. Rev., Vol. 115, 2015: pp. 6265-6311 ; TANG et al., “Large Scale Synthesis of Janus Submicrometer Sized Colloids by Seeded Emulsion Polymerization, ” Macromolecules, Vol. 43, 2010: pp. 5114-5120; and PHAM et al., “Synthesis of Polymeric Janus Nanoparticles and Their Application in Surfactant- Free Emulsion Polymerizations,” Polym. Chem. Vol. 6, 2015: pp. 426-435, each of which is hereby incorporated by reference in their entirety.

[0096] In embodiments, Janus particles care synthesized, for example, as described in Nisisako et al., “Synthesis of Monodisperse Bicolored Janus Particles with Electrical Anisotropy Using a Microfluidic Co-Flow System,” Adv. Mater, 2006, Vol. 18, 2006: pp. 1152-56. In embodiments, one element of anisotropy in the Janus particle is in density and a second element of anisotropy is in the optical properties.

[0097] Janus particles, including for example, synthetic approaches as described Su et al. “Janus particles: design, preparation, and biomedical applications”, Materials Today Bio 4, (2019) 100033; Wang et al. “Application of Janus Particles in Point-of-Care Testing”, Biosensors 2022, 12, 689; Claudia Marschelke et al., “Janus particles: from concepts to environmentally friendly materials and sustainable applications,” Colloid and Polymer Science, Vol. 298, 2020: pp. 841-65; Safaie & Ferrier Jr., “Janus nanoparticle synthesis: Overview, recent developments, and applications,” J. Appl. Phys., Vol. 127, No. 170902, 2020; and Saqib et al., “Microfluidic Methods in Janus Particle Synthesis”, Int J Nanomedicine. Vol. 17, 2022: pp. 4355-66, each of which is hereby incorporated by reference in their entirety. In embodiments, one or more components of magnetochromic particle are manufactured using synthesis incorporating methods including microfluidicsynthesis, templated synthesis, assembly of the two faces in solution ( / . e., by heterodimerization of particles), polymer-related methods (e.g., such as emulsion polymerization), anisotropic surface modification of individual particles, as well as other methods. In embodiments, microfluidic methods are used to fabricate Janus particles at both the nanoscale and microscale, where the Janus particles can incorporate two or more materials with distinct optical property and then be encapsulated in a shell to produce an encapsulated magnetochromic particle. In embodiments, one or more components of the particles are manufactured using one or more methods, or combinations of steps, for example, as described in Bezelya et al., “Microfluidic Devices for Precision Nanoparticle Production,” Micro, Vol. 3, 2023: pp. 822-66; Qu et al., “Fabrication of shape-tunable micromotors based on mass transfer and phase separation,” J. Materi. Sci. (2023), doi.orq / 10.1007 / s 10853-023-09062-6; Song et al., “Recent advances in microfluidic fiber-spinning chemistry,” JPolym Sci. 2023: pp. 1-16; Lin et al., “Scalable production of microscopic particles for biological delivery,” Mater. Adv., Vol. 4, 2023: pp. 2885-908; Lui et al., “Recent advances in the microfluidic generation of shape-controllable hydrogel microparticles and their applications”, Green Chemical Engineering, doi.org / 10.1016 / i.qce.2023.02.002; Pilkington et al., “A Microfluidic Platform for the controlled synthesis of architecturally complex liquid crystalline nanoparticles”.” Scientific Reports, Vol. 13, 12684, (2023); Saqib et al., “ Microfluidic Methods in Janus Particle Synthesis,” International Journal of Nanomedicine, Vol. 17, 2022: pp. 4355-4366; Xie et a / ., ’’Microfluidic synthesis as a new route to produce novel functional materials,” Biomicrofluidics, Vol. 16, 041301, (2022); Baah et al., “Microfluidics for particle synthesis from photocrossl inkable materials,” Microfluid Nanofluid, Vol. 12, 2014: pp. 657-62; Agha et al., “A review on microfluidic-assisted nanoparticle synthesis, and their applications using multiscale simulation methods,” Discover Nano, Vol. 18, No. 1 (2023); Gimondi etal., “Microfluidic Devices: A Tool for Nanoparticle Synthesis and Performance Evaluation,” ACS Nano, Vol. 17, 2023: pp. 14205-28; Hao et al., “Microfluidics for Silica Biomaterials Synthesis: Opportunities and Challenges,” Biomaterials Science, Vol. 6, No. 6, 2019: pp. 2218- 40; and Kim et al., “Microfluidic preparation of monodisperse polymeric microspheres coated with silica nanoparticles,” Scientific Reports, (2018) Vol. 8, 8525 (2018), the entire contents of each is herein incorporated by reference.

[0098] In embodiments, and in reference to Figs. 7A-7D, methods herein are adaptable to produce variations in the magnetically-responsive particles, for example, altering the shape / geometry to include cylindrically-shaped, rod-shaped, oblate spheroid-shaped, and other anisotropic magnetic Janus microparticles made using microfluidics. In embodiments, and in reference to Fig. 7A, microscopic analyses demonstrate that particle are reproducibly manufacturable on the micron scale (e.g., -50-1000 pm). Inembodiments, and in reference to Fig. 7B, methods herein are adaptable to attached the magnetic material to the outer surface of the particle, and / or to be infused and / or embedded within and throughout the particle (e.g., as shown in Fig. 7C). In embodiments, and in reference to Fig. 7D, methods herein are adaptable to generate magnetic Janus particles in which there are (i) two spatially distinct magnetic materials; (ii) a continuous phase of magnetic materials confined to a band; (iii) a dimer of spherical particles, with each particle having magnetic material; (iv) partially merged dimer of spherical particles; (v) a rod-shaped particle with a continuous phase of magnetic materials; and (vi) magnetic material is associated with a single colored material.

[0099] In embodiments, methods herein produce a magnetochromic particle which comprises a variety of shapes and / or geometries. In embodiments, the shape substantially similar to one or more of a truncated teardrop shape, champagne flute shape, wine glass shape, round-bottomed shape, tumbler shape, eggshape, paraboloid, prolate hemispheroid, oblate hemispheroid, hemispherical, elliptical, cylindrical, trigonal pyramid, pentagonal pyramid, hexagonal pyramid, a regular polygonal shape with a truncated portion, a truncated square pyramid, a truncated cone, a truncated cone where the top plane and bottom plane are not parallel. In embodiments, the shape is substantially concave and / or convex 3-dimensional shape. In embodiments, the terms “approximately” or “substantially” in reference to shapes / geometries of particles refers to the general shape / geometry and any and all variations that would reasonably be construed or described as resembling the form of that shape / geometry.

[0100] In embodiments, methods herein comprising producing magnetochromic practices using two or more materials which differ in density and / or optical property. In embodiments, the first material is a less dense optical material and the second material is a denser optical material. In embodiments, each material occupies approximately one hemisphere of the spherical (or substantially spherical) magnetochromic particle. In embodiments, the first, less dense material occupies most of the volume of the magnetochromic particle, while the second, denser material occupies less volume. In embodiments, the less dense optical material or the denser optical occupies about or at least about 1%, 2% 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12% 14%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, or more than 90%, such that the sum of the percentages of the at least two materials add to 100%. In embodiments, methods herein utilize materials with difference in density, as well as difference in optical property, such that the difference in density correlates to the difference in optical property in the particle. In embodiments, the less dense material has a first optical property (e.g., color), and the more dense material has a second optical property (e.g., color),where they are spatially aligned. In embodiments, the optical properties do not need to correspond to the mass distribution.

[0101] In embodiments, the magnetochromic particle is substantially spherical or non-spherical, and exhibits smooth or rough surfaces. In embodiments, magnetochromic particle and / or the outer shell has a shape / geometry that has one or more axes of symmetry; alternatively, in embodiments, each have a shape / geometry that is asymmetrical. In embodiments, the magnetochromic particle has a regular pattern of roughness features on the outer surface of the particle and / or on the outer surface of the shell (e.g., for encapsulated magnetochromic particles). In embodiments, the one or more roughness features is regularly or irregularly shaped. In embodiments, the one or more roughness features appears in a regular and / or irregular pattern. In embodiments, the roughness features are not regularly-shaped, do not cover the entire surface; are not uniform in shape / size, and are not regularly spaced. In embodiments, the one or more roughness features is a variation in a surface smoothness that alters the degree of reflectivity of the surface at one or more wavelengths, and / or affects the movement, friction, or packing features of the core magnetochromic particle(s) within an outer shell. For example, in embodiments, methods herein produce “raspberry-shaped” magnetochromic particles with “lobes” which are grown onto the surface of core particles, and which may function as roughness features.Magnetic Materials and Attachment

[0102] In embodiments, the method comprises attaching the magnetic material to the one or more particles to generate one or more magnetically-responsive particles. In embodiments, the attaching step is performed such that the particles are labeled in a 1 :1 stoichiometric ratio (e.g., a single magnetic portion per particle), where each particle comprises magnetic material at substantially one location.

[0103] In embodiments, the attaching further comprises a click-chemistry reaction to adhere the magnetic material to the one or more particles. In embodiments, generating particles includes the chemical method of click chemistry, a class of simple, atom-economy reactions commonly used for joining two molecular entities of choice. Click reactions, in embodiments, occur in a single vessel, are not sensitive to water, generate minimal byproducts, and are "spring-loaded" — characterized by a high thermodynamic driving force that quickly and irreversibly drives the reaction to high yield of a single reaction product, with high reaction specificity (in some cases, with both regio- and stereo-specificity). In embodiments, the clickchemistry reaction comprises one or more of azide-alkyne cycloaddition, thiol-click reaction (thiol-ene, thiolyne, thiol-isocyante), Diels-Alder reaction, nitrile oxide cycloaddition, tetrazole cycloaddition, oxime formation,and 1 ,3-dipolar azide-alkyne cycloaddition (CuAAC). In embodiments, attaching the magnetic material to the particles includes other chemical methods well-known (especially in life sciences) for joining two entities together including in non-limiting examples, streptavidin-biotin coupling, maleimide-based reactions, and carbodiimide-based reactions.

[0104] In embodiments, attaching further comprises microfluidics to adhere the magnetic material to the one or more particles (e.g., as shown in Figs. 6A-6B). In embodiments, magnetically-responsive particles are generated with the attaching, fusing, or adhering of the two materials occurring under microfluidic conditions, for example, as described in Saqib et al., "Synthesis of Anisotropic Magnetic Polymeric Janus Particles by In Situ Separation of Magnetic Nanoparticles in a Microfluidic Device,” the entire contents of which are hereby incorporated by reference. In embodiments, a microfluidic chamber having two of more continuous phase or dispersed phase inlets disperse droplets which form Janus particles having a magnetic material. In embodiments, the microfluidic chamber has a portion for curing the particles (e.g., solidifying, polymerizing, etc.). In embodiments, the curing step includes a thermal treatment, such as microwave treatment, UV radiation exposure, heat induction, etc., of the particles alongside applying a magnetic field to induce anisotropy (e.g., a magnetic dipole) in the magnetically-responsive particles as they solidify.

[0105] In embodiments, the one or more particles and / or one or more magnetically-responsive particles and / or one or more magnetically-responsive optically-variable particles comprises a dimension (e.g., diameter, length, width, etc.) ranging from about 10 nm to about 1000 pm in size. In embodiments, the dimension is about or at least about 10 nm, about or at least 20 nm, about or at least about 30 nm, about or at least about 40 nm, about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm, about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or at least about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm, about or at least about 2 pm, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm, about or at least about 200 pm,about or at least about 300 pm, about or at least about 400 pm, about or at least about 500 pm, or about or at least about 1000 pm.

[0106] In embodiments, the magnetic material comprises one or more of magnetic beads and magnetic particles. In embodiments, a “magnetic material,” or “magnetic bead or particle,” as used herein is composed of any suitable known material that responds to a magnetic field. In embodiments, the magnetic beads and / or magnetic particles are about or less than about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 5%, or 1 %, of the dimension (e.g., diameter, length, width) of the one or more particles they are attached to. In nonlimiting examples, the magnetic material are beads or particles that are 5-fold to 100-fold smaller than the one or more particles.

[0107] In embodiments, the magnetic material includes magnetic particles (e.g., nanoparticles) and / or magnetic beads having a variety of magnetic qualities, including being one or more of ferromagnetic, ferrimagnetic, antiferromagnetic, diamagnetic, paramagnetic, superparamagnetic, and antiferromagnetic.

[0108] In embodiments, the magnetic material includes, in non-limiting examples, iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), manganese (Mn), chromium (Cr), samarium (Sm), and the like, including chemical derivatives thereof. Typical derivatives, in embodiments, include alloys or oxides of metals, e.g., alloys, intermetallic, and / or oxides of Fe, Co, Ni, Zn, Mn, Sm, or any combination thereof. In embodiments, the oxides are of iron, e.g., Fe2O3, FeO, or Fe3O4. In embodiments, the magnetic particles are composed of ferrite material or of doped materials, including in non-limiting examples of one or more of Co, Ni, Zn, or MmFexOy.

[0109] In embodiments, the magnetic material is composed of organic, carbon-based, and / or biomolecule-based magnetic material including, for instance in non-limiting examples, one or more of tetracyanoethylene (TCNE) salts, [Fe(C5Me5)2]+|TCNE]-, LifTCNE], [Mn"TPP]|TCNE]« (TPP = tetraphenylporphyrin), [Fell(TCNE)(NCMe)2][FelllCl4], Mn"(TCNE)l(OH2), Mn"(TCNE)[C4(CN)8]i / 2, Fe(TCNE)[C4(CN)8]i / 2, Mn"(TCNE)3 / 2(l3)i / 2, V"|TCNE]x (x « 2), CzHsCINsSe^ magnetic biopolymers.

[0110] In embodiments, the magnetic material includes or comprises a magnetite. In embodiments, a magnetite is a biodegradable, biocompatible, non-toxic molecule that has can be used as an imaging contrast agent (e.g., an MRI contrast agent). In embodiments, other magnetic particles, such as red and / or black iron oxides (Fe2O3, FeO, and / or FesO4) can also be used.

[0111] In embodiments, the magnetic material acts as an optical agent, imbuing the manufactured particle with a color, reflectance, emission, scattering, etc., property based on the material used.

[0112] In embodiments, the magnetic material is a transparent magnetic material. In embodiments, transparent magnetic materials are a class of materials that exhibit both transparency to visible light and magnetic properties. In embodiments, the transparent magnetic material includes materials used in other applications, such as optoelectronics, magneto-optical devices, and transparent electronics, for example as described in: Loste, et al., “Transparent polymer nanocomposites: An overview on their synthesis and advanced properties,” Progress in Polymer Science (2018); Kobayashi, et al., “Optically Transparent Ferromagnetic Nanoqranular Films with Tunable Transmittance,” Sci Rep, Vol. 6, No. 34227, 2016, doi.org / 10.1038 / srep34227; Babu, et al., “Indium oxide: A transparent, conducting ferromagnetic semiconductor for spintronic applications,” Journal of Magnetism and Magnetic Materials (2016), doi.org / 10.1016 / j.jmmm.2O16.05.007, Chavan, et al., “A Brief Review of Transparent Conducting Oxides (TCP): The Influence of Different Deposition Technigues on the Efficiency of Solar Cells,” Nanomaterials Vol. 13, No. 1226, 2023; Ye, et al., “Research and Progress of Transparent, Flexible Tin Oxide Ultraviolet Photodetector,” Crystals, 2021 , Vol. 11, No. 1479; Gul S, et al., “A Comprehensive Review of Magnetic Nanomaterials Modern Dav Theranostics,” Front. Mater. Vol. 6, No, 179, 2019; Rita Policia, et al., “Transparent Magnetoelectric Materials for Advanced Invisible Electronic Applications,” Adv. Electron. Mater. 2019, 1900280, each of which is hereby incorporated by reference in their entirety.

[0113] In embodiments, transparent magnetic materials include the family of diluted magnetic semiconductors (DMS) or oxide-based transparent magnetic materials. In embodiments, DMS are formed by introducing a small concentration of magnetic ions, such as transition metal ions, into a semiconductor matrix, where the magnetic properties arise from the interaction between the magnetic ions and the host lattice. In embodiments, oxide-based transparent magnetic materials are typically composed of a transparent oxide matrix e.g., indium tin oxide) doped with magnetic ions.

[0114] In embodiments, othertypes of transparent magnetic particles and materials include those based on iron oxide nanoparticles, such as magnetite (Fe3O4) and maghemite (y-Fe2O3), which can be engineered to have a transparent nature while retaining their magnetic properties. In embodiments, stimuli-responsive elements include ferrite nanoparticles, like cobalt ferrite (CoFe2O4) or nickel ferrite (NiFe2O4), which can be synthesized in a way to achieve transparency. In embodiments, stimuli-responsive elements include rare earth iron garnets, such as yttrium iron garnet (YsFesO^), which can exhibit a strong magneto-optical effectwhile maintaining a degree of transparency. In embodinest, additional examples of transparent magnetic particles and materials include Sn-doped I n2Os, FeSiB (Fe72.5Si12.5B15), and FesCosAligFez. In embodiments, transparent magnetic particles and materials can be incorporated into polymers to form particles or beads that are suitable for the structures described herein.

[0115] In embodiments, the magnetic material includes magnetite (e.g., FesC ) alongside or in place of a number of components, e.g., including metals (e.g., magnetic elements, such as iron, nickel, cobalt, chromium, and / or manganese) and / or magnetic organic polymers (see, e.g., Rajca et al., “Magnetic Ordering in an Organic Polymer,” Science, 294, 2001 : pp. 1503-1505, the entirety of which is hereby incorporated by reference). In embodiments, the particles are composed of 100% metal oxide (e.g., magnetite), or can be composites including other components, e.g., including polymers, polymer-bonded magnets, and / or polymers comprising chromophores.

[0116] In embodiments, the magnetic material includes a magnetic bead. In embodiments, the magnetochromic particle includes multiple magnetic beads / particles contained within a polymer bead, e.g., polystyrene. In embodiments, the magnetic material is a spherical magnetic bead, or a spherical polymer- based bead with one or more magnetic particles contained therein. In embodiments, the magnetic material comprises magnetic iron oxide nanoparticles embedded in polyethylene glycol) diacrylate.

[0117] In embodiments, magnetic material is magnetized, e.g., capable of being attached to iron (e.g., can project their own magnetic field), and are capable of producing a magnetic field outside themselves, either naturally or by induction. In embodiments, a magnetic field can be induced in the particles, e.g., during manufacture and / or after use, such as by exposing the particles to a strong magnetic field, e.g., an electromagnet.

[0118] In embodiments, the magnetic field (e.g., magnetic flux density) created by the magnetic material (e.g., either on its own or in the magnetochromic particle) and / or the magnetic field strength of a magnet used during the method to orient or separate particles is from about or at least about 200 gauss to about or at least about 25,000 gauss (10,000 gauss = 1 Tesla). In embodiments, the magnetic field is about or at least about 200 gauss, about or at least about 500 gauss, about or at least about 800 gauss, about or at least about 1 ,000 gauss, about or at least about 2,500 gauss, about or at least about 12,500 gauss, about or at least about 15,000 gauss, about or at least about 20,000 gauss, or about or at least about 25,000 gauss. In embodiments, the magnetic particles retain the ability to project a magnetic field, i.e., they can becomepermanent magnets. In embodiments, the particles can lose the ability to produce a magnetic field over time, and a field can be re-induced by re-application of a strong magnetic field.

[0119] In embodiments, magnetic particles are prepared using any method known to those of skill in the art. For example, in embodiments, magnetic particles are formed by precipitation methods, high temperature methods, or other methods known to those skilled in the art. In embodiments, the magnetic particles can be fabricated by mechanical milling, supercritical CO2-based precipitation of magnetite / polymer microparticles, or micelle synthesis. After fabrication, in embodiments, the particles can be sorted for size and quality, e.g., by centrifugation or filtration. A number of magnetic particles are commercially available, for example in embodiments, from Ademtech, 33600 Pessac, France; Bangs Laboratories, Inc., Fishers, IN, U.S.A.; Pea Ridge Iron Ore Co., Sullivan, MO, U.S.A.; Quantum Magnetics, Division of Clemente Associates, Inc., Madison, CT, U.S.A.; among others. In embodiments, magnetic particles can be sterilized using methods known in the art, e.g., heat, chemical, or radiation sterilization.

[0120] In embodiments, methods herein include applying a magnetic field one or more times to the one or more magnetically-responsive particles. In embodiments, a first magnetic field is applied after the magnetic material and particle (e.g., Janus particle, polymer bead, etc.) are attached, joined, fused, or otherwise combined such that the magnetic field is used to purify, isolate, or otherwise separate the magnetically- responsive particles from those that do not comprise magnetic material. In embodiments, a second magnetic field is applied to the one or more magnetically-responsive particles to orient the particles on a surface such that a portion of the exposed surface area of each is coated with an optical agent. In embodiments, this is done to ensure that the particles that results from manufacture will each exhibit identical optical properties relative to the direction of a magnetic field.

[0121] In embodiments, methods herein include disposing the one or more magnetically-responsive particles onto a surface to generate a 2-dimensional (2-D) array of the one or more magnetically-responsive particles. In embodiments, disposing the particles onto the surface comprises spraying, evaporating, or blotting the particles onto the surface. For example, in embodiments, the one or more magnetically- responsive particles are suspended in a liquid with a volatile solvent, where the liquid is sprayed onto a surface to evenly distribute the particles on the surface and the volatile solvent is evaporated.

[0122] In embodiments, after magnetically-responsive particles are disposed on a surface, there are a number of ways to manipulate them. For instance, in non-limiting embodiments, Figs. 14A-14E show some examples of how magnets are positioned to effect the movement of particles (e.g., for deposition of opticalagents, etc.). In embodiments, such movement occurs prior to, during, or after the introduction of optical components or optical properties (e.g., a first optical agent, moving by a defined amount then applying a second optical agent, etc.). For example, in embodiments and in reference to Figs. 14A and 14B, arrays of particles are position such that the magnetic portion (show as black) is positioned facing up (Fig. 14A) or down (Fig. 14B). It should be clear that Figs. 14A and 14B are non-limiting, insofar as they are meant to depict arrays of magnetically-responsive Janus particles (or non-JP-based magnetochromic particles) in any two non-identical orientations.

[0123] In embodiments, once particles are in substantially the same orientation (e.g., all with the magnetic part of the Janus particle facing up as shown in Fig. 14A), then a magnet can be positioned in multiple different positions, as shown in Figs. 14C and 14D, to initiate particle movement. In embodiments, and as shown in Figs. 14C-14D, six different orientations for positioning are illustrated - the four sides in the plane of the substrate, and above and below. In embodiments, and in reference to Fig. 14E, from a given position, a magnet can be moved in the x, y, and / or z direction to initiate movement of magnetically- responsive Janus particles (or non-JP-based magnetochromic particles) from one orientation to another orientation.

[0124] Those skilled in the art, with the benefit of this disclosure in its entirety, will appreciate that the positioning and direction of motion of the magnet required to effect particle movement depends, in part, on the shape of the particle and the positioning of the magnetic field-responsive element or elements within the particle.

[0125] In embodiments, the surface the particles are disposed upon comprises a substrate composed of one or more of thin film, plastic, polymer, paper, glass, sapphire, diamond, silicon, organic polymer, organic material, biological polymer, metal oxide, quartz, plastic, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers (TPE), acrylonitrile butadiene styrene (ABS), epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer (COC) cyclic olefin polymer (COP), poly dimethyl siloxane (PDMS), poly ether ester ketone (PEEK), polyetherimide (ULTEM), and nylon. In embodiments, the surface the particles are disposed upon becomes a part of the particle-based composition, such as in manufacturing a film, tape, paper, wrapper, etc. In embodiments, the surface acts as a temporary substrate to orient particles during the manufacturing process.

[0126] In embodiments, the surface comprises one or more detents, indentations, or markers, which enable the one or more magnetically-responsive particles to be disposed in the 2-D array. In embodiments, the 2-D array comprises an evenly-spaced distribution (e.g., with about or at least about 0.01 pm to about or at least about 1 cm distance between particles).

[0127] In embodiments, methods herein include coating at least a portion of the exposed surface area of the one or more magnetically-responsive particles with at least a first optically active agent to generate one or more magnetically-responsive optically-variable particles. In embodiments, coating comprises spraying, sputtering, painting, glow discharging, or otherwise applying at least one optically active agent onto at least a portion of the external surface area of the one or more magnetically-responsive particles.

[0128] In embodiments, coating includes the use of a mask to filter a section or portion of each particle to be coated. The mask, in embodiments, includes a second discontinuous substrate with regularly spaced slits or holes that that substantially correspond to and overlap with the position of the particles affixed in the array.

[0129] In embodiments, methods include applying at least a third magnetic field to the one or more magnetically-responsive optically-variable particles to re-orient the particles such that a different portion of the surface area of each is exposed to re-coat the particles at a different portion or section of their surface area. For example, in embodiments, substantially spherical particles are re-oriented by rotation using a magnet to repeatedly apply optically active agents. In embodiments, a mask and magnetic field are used to reorient particles such that they are all identically coated with various optical agents. In embodiments, the magnetic field is flipped 180° relative to its original position during a first coating (e.g, the magnet is moved from the left side to right side of the surface the particles are disposed upon), where doing so will substantially re-orient the magnetically-responsive optically-variable particles such that an opposite surface is exposed (e.g, to coat each hemisphere a different color). In embodiments, the second optically active agent disposed after the third magnetic field is applied is distinct from the first optically active agent (e.g, where this is repeated any number of times).

[0130] Alternatively, in embodiments and in reference to Figs. 8A-8H, magnetic material attachment occurs outside of solution and after depositing the particles into a 2-D array on a planar material. In embodiments and in reference to Fig. 8A, a particle, for example, in the shape of an oblate spheroid (e.g, shown formulated into solution in Fig. 8B) are deposited onto a substantially planar material having a 2-D array of features (ellipses) designed to fit one particle per feature (e.g, as shown in Figs. 8C-8D). Inembodiments and in reference to Fig. 8E, the magnetic material (e.g., a magnetic particle) are attached to each particle within the array. In embodiments and in reference to Fig. 8F, a magnetic field is applied to orient the particles in the array such that the magnetic particles are all facing the magnet and the particles are each in the same orientation relative to the magnetic field. In embodiments and in reference to Fig. 8G, an optically active agent (e.g., a colored material shown as gray) is deposited onto the surface of the particles. In embodiments and in reference to Fig. 8H, after release from the substrate the resulting particle has a magnetic element and at least two distinct optical properties.Formation of Encapsulants

[0131] In embodiments, methods include encapsulating the magnetically-responsive particles in an outer shell. In embodiments, encapsulating the magnetically-responsive particles in an outer shell comprises performing one or more of interfacial polymerization, in situ polymerization, coacervation, layer-by-layer growth, adsorption, sol-gel encapsulation, suspension crosslinking, lyophilization, spay drying, co-extrusion, fluidized bed spray coating, and phase inversion precipitation.

[0132] In embodiments, the presence of magnetically-responsive elements are exploited in the synthesis and / or purification of species related to encapsulated, yolk-shell magnetically responsive Janus particles, as shown in Fig. 12 and Fig. 13. In embodiments, and in reference to Fig. 12A, an illustration of a magnetically-responsive particle is shown with two different optical regions (shown as black and white). In embodiments, the magnetic element could be associated with the black hemisphere or surface of the black hemisphere, the white hemisphere or the surface of the white hemisphere, or in any one location or multiple locations in the particle. In embodiments, coating and / or surface modification of the particle, e.g., as shown by the gray colored substance in Fig. 12B, may lead to side products, including but not limited to particles of the material as shown in Fig. 12C (e.g., satellite particles).

[0133] In embodiments, methods herein include purifying a (single) substance. In embodiments, one way to separate the material, e.g., of Fig. 12B from that of the material of Fig. 12C, is to place the mixture of substances into a fluid, e.g., as shown in Fig. 12D, and use a magnetic field to attract the particles of Fig. 12B to the side of the flask, e.g., as shown in Fig. 12E, after which the solution containing the particles of Fig. 12C can be decanted away or otherwise separated.

[0134] In embodiments, methods herein use the same concept to purify magnetically responsive, encapsulated yolk-shell particles. For example, in embodiments and in reference to Fig. 13A, an optically variable Janus particle (shown with black and white hemispheres) is coated with a sacrificial layer (shown asdark gray), which is, in turn, encapsulated in a thin shell (shown as black). In embodiments, the magnetically responsive element is associated with the core Janus particle or with an outer shell, or with both materials. In embodiments, to make a particle, e.g., as shown in Fig. 13A, into an encapsulated, yolk-shell geometry, the dark gray layer is removed, e.g., as shown in Fig. 13B. However, in embodiments, this process may generate residual amounts of the sacrificial layer (or species related to the sacrificial layer) outside of the shell, e.g., as shown in Fig. 13C. In embodiments, methods herein include placing the substances, e.g., of Fig. 13B and Fig. 13C in a fluid solution, e.g., as shown in Fig. 13D, such that a magnet can be used to attract the particles of Fig. 13B to the side of the flask, e.g., as shown in Fig. 13E, after which the solution containing the particles of Fig. 13C can be decanted away or otherwise separated.

[0135] In embodiments, the outer shell is optically transparent from the x-ray and / or ultraviolet (UV) region of radiation (wavelengths >10 nm) to the microwave / radio region (<10 cm). In embodiments, the at least one layer of outer shell comprises at least a portion that transmits electromagnetic radiation in the ultraviolet, visible, or near-IR regions of the spectrum (between 300-1200 nm). In embodiments, layers of the outer shell are used to filter or select for specific wavelengths or ranges of wavelengths of radiation. In embodiments, the shell transmits a percentage of the incident electromagnetic radiation through the at least one layer of outer shell of about 100%, or about 99%, or about 98%, or about 97%, or about 96%, or about 95%, or about 94%, or about 93%, or about 92%, or about 91%, or about 90%, or about 85%, or about 80%, or about 75%, or about 70%, or about 65%, or about 60%, or about 55%, or about 50%, or about 40%, or about 30%, or about 20%, or about 10%, or about 5%, or about 4%, or about 3%, or about 2%, or about 1 %, or about 0.5%, or about 0.4%, or about 0.3%, or about 0.2%, or about 0.1 %, or about 0.05%, or about 0.04%, or about 0.03%, or about 0.02%, or about 0.01 %, or 0.005%, or about 0.001 %, relative to the intensity or amount of incident radiation that impinges on the material of the outer shell. In embodiments, the outer shell comprises at least a portion that is opaque and substantially blocks transmission of EM radiation in one or more ranges.

[0136] In embodiments, the outer shell improves the penetration of light into the particle and reduces scattering. In embodiments, there are various methods for making optically transparent shells for particles, depending on the type of shell material and the desired properties of the final particles. For example, in embodiments, the method of manufacturing the shell includes (1) layer-by-layer assembly: this method involves sequentially depositing alternating layers of oppositely charged polymers or other materials onto the surface of the nanoparticle core. In embodiments, the resulting shell is made to be optically transparent by choosing materials with high transparency in the desired wavelength range. In embodiments, the method ofmanufacturing the shell includes (2) sol-gel methods which involve hydrolyzing and condensing a precursor material in solution around the nanoparticle core, resulting in the formation of a porous network that is annealed to create a solid, transparent shell. In embodiments, common precursor materials include metal alkoxides and silicon alkoxides. In embodiments, the method of manufacturing the shell includes (3) emulsion-based methods, where the core-shell nanoparticles are formed by emulsifying a solution of the core material in a solution of the shell material, followed by polymerization or crosslinking of the shell material to form a solid shell around the core. In embodiments, careful control of the emulsion conditions, such as the surfactant type and concentration, is done to create optically transparent shells. In embodiments, the method of manufacturing the shell includes (4) gas-phase methods, for example, involving evaporating a precursor material in a high-temperature gas-phase reactor and depositing the resulting vapor onto the nanoparticle core. In embodiments, controlling the reaction conditions, such as temperature and pressure, is done to create a uniform, optically transparent shell.

[0137] In embodiments, optically transparent shells are synthesized, for example, as in Deng et al., “Transparent, Thermally Stable and Mechanically Robust Superhydrophobic Surfaces Made from Porous Silica Capsules”, Adv. Mater, 2011 , 23, 2962; Ernawati et al, “Hollow Silica as an Optically Transparent and Thermally Insulating Polymer Additive”, Langmuir 2016, 32, 338-345; Liang et al, “Nature of Electromagnetic- Transparent SiO2Shell in Hybrid Nanostructure Enhancing Electromagnetic Attenuation”, J. Phys. Chem. C 2016, 12,967-12,973; Dolatyari et al, “Transparent Display using a guasi-array of Si-SiO2 Core-Shell Nanoparticles”, Scientfic Reports 2019, 9:2293; and Sangermano et al, “Synthesis of Au@SiO2 Core / Shell Nanoparticles and their Dispersion into an Acrylic Photocurable Formulation: Film Preparation and Characterization”, Macromol. Chem. Phys. 2008, 209, 2343-2348, the entire contents of each of which are herein incorporated by reference.

[0138] In embodiments, at least one layer of the shell comprises performing one or more of mesoporous material synthesis, soft-templating, calcination, and / or extraction. For example, in embodiments, the outer shell is produced using a hollow yolk-shell particle method including: A) producing a silica core, B) coating the silica core with polystyrene (PSt) to form a polystyrene layer around the silica core (e.g, a dissolution layer); C) forming a silica (SiO2) shell around the PSt layer; D) calcination at high temperature (500°C for 4 hr.) to create a void space between the silica shell and core; and E) etching with NH3. In embodiments, the method includes dispersing thermally responsive polymers within the void space or cavity between the shell and encapsulated particle(s). In embodiments, the method includes applying one or more protective coating(s), for example, in place of the PSt layer or in addition to it. In embodiments, the method includes ahardening step after etching to close or seal any pores in the shell layer. In embodiments, the outer shell comprises a single, uniform thickness and / or varying thicknesses.

[0139] In embodiments, the outer shell contains polymeric materials. In embodiments, the polymers comprise one or more of plastics, acrylic resin, styrene acrylic copolymer, vinyl acetate ethylene copolymer, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyurethane, epoxy resin, alkyd resin, cellulose acetate, silicone resin, a fluoropolymer resin, chlorinated rubber, a copolymer derived from maleic anhydride, ethylene vinyl acetate, polyethylene, polypropylene, polyamides (nylons), polyester resins, polybutadienes, thermally responsive polymers, latex, hydrocarbons, crude oil derivatives and / or petroleum derivatives, poloxamers, styrene-butadiene block copolymers, polymethylmethacrylate, polybutylmethacrylate, poly(tert- butyl acrylate)-poly(3-(triethoxysilyl)propyl methacrylate) (PtBA-PTPM), polystyrene latex polymer, carboxylated latex polymer, aminated latex polymer, colored polystyrene polymer (dye-infused and / or pigment-infused), colored polystyrene-based carboxylated latex polymer (dye-infused and / or pigment- infused), fluorescent polystyrene-based polymers, fluorescent polystyrene-based carboxylated latex polymers, fluorescent aminated polystyrene-based polymer, surfactant-free polystyrene, carboxylated surfactant-free polymer, polymethyl methacrylate (PMMA) latex polymer, and / or divinylbenzene-crosslinked polystyrene latex, plasticized polyvinyl chloride, plasticized nylon, plasticized polyethylene terephthalate, polyacrylonitrile, polychlorotrifluoroethylene, poly-4, 4'-isopropylidenediphenylene carbonate, polyethylene vinyl ester, polyvinyl chloride-diethyl fumarate, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers, acrylonitrile butadiene styrene, epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer, cyclic olefin polymer, poly dimethyl siloxane, poly ether ester ketone, polyetherimide, and combinations thereof.

[0140] In embodiments, the outer shell includes naturally occurring polymers and / or biological polymers. In embodiments, the one or more biological polymers comprise nucleic acid (DNA, RNA), amino acid (peptide, protein), polysaccharide, and / or lipid.

[0141] In embodiments, the outer shell includes one or more inorganic materials. In embodiments, the inorganic materials comprise one or more of alumina, silica, titania, silicon nitride, zirconia, copper oxide, iron oxide, cobalt oxide, silver, gold, aluminum, copper, tin oxide, nickel oxide, lead oxide, glass, quartz, sapphire, inorganic glasses, diamond, diamond-like materials, zinc oxide, and manganese oxide.

[0142] In embodiments, a geometric element of the magnetochromic particle, for example in reference to Figs. 1A-1 B, is that the particle is spatially confined within the interior volume of the outer shell 108. Inembodiments, the inner core particle is described, for example, in Kuk S, et al., “Rattle-Structured Upconversion Nanoparticles for Near-IR-lnduced Suppression of Alzheimer's 6-Amyloid Aggregation,” Small, Vol. 13, No. 11 , 2017: pp. 1-8; and Zhang et al., “Mesoporous Multifunctional Upconversion Luminescent and Magnetic “Nanorattle” Materials for Targeted Chemotherapy,” Nano Lett, Vol. 12, 2012: 61-67, both of which are hereby incorporated by reference in their entirety.

[0143] In embodiments, the outer shell (e.g., such as the outer shell 108 of the particle of Figs. 1A-1B) comprises a dimension (e.g., a thickness, diameter, or radius) of about 10 nm to about 1 mm, for example, of about or at least 10 nm, about or at least 20 nm, about or at least about 30 nm, about or at least about 40 nm, about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm, about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or at least about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm (1 pm), about or at least about 2 pm, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm, about or at least about 200 pm, about or at least about 300 pm, about or at least about 400 pm, about or at least about 500 pm, or about or at least about 1000 pm (1 mm).

[0144] In embodiments, the outer shell of the magnetochromic particle is continuous or discontinuous, spherical or non-spherical, and exhibits smooth or rough surfaces (e.g., inner and / or outer). In embodiments, such a design allows for a gas, liquid, semisolid, or other matter to permeate through the outer shell into the interior volume. In embodiments, any external shell configuration is acceptable in magnetochromic particles such that the external shell does not move in response to the stimulus, and the magnetically-responsive particles remains confined within the shell and able to move in response to a magnetic field. Thus, in embodiments, the outer shell is thick and / or strong enough not to rupture during the movement of the particle, and if discontinuous or porous, there are no discontinuities ( / .e., pores or holes) large enough for the particle to escape. In embodiments, the discontinuities in the shell comprise about or up to about 0.1 %, about or up to about 1 %, about or up to about 10%, about or up to about 50% or more of the total surface area of theouter shell, provided that none of the pores have a cross-sectional dimension that is larger than the smallest external dimension of the core particle.

[0145] In embodiments, the outer shell is porous during synthesis (e.g., removed as a sacrificial layer), and then converted to a non-porous state. For example, in embodiments, with respect to silica-based shells, numerous methods exist to convert a porous silica shell to a non-porous silica shell. In embodiments, silica- based shell conversion for the manufacture of magnetochromic particles is performed, for example, as described in Mochizuki et al., “Development of Non-Porous Silica Nanoparticles towards Cancer Photo- Theranostics”, Biomedicines 2021, 9, 73; Zhou et al., “Design and pharmaceutical applications of porous particles”, RSC Adv. 2017, 7, 39490; Maiti et al., “Advancements in organic and inorganic shell materials for the preparation of microencapsulated phase change materials for thermal energy storage applications”, RSC Sustainability 2023, 1 , 665; and Tang et al., “Nonporous silica nanoparticles for nanomedicine application”, Nano Today 2013, 8, 290-312, the entire contents of each of which are herein incorporated by reference

[0146] In embodiments, the outer shell fully encapsulates the one or more magnetically-responsive optically-variable particles, resulting in a bounded internal volume. In embodiments, the magnetically- responsive particle is suspended or otherwise shares the internal volume with a gas, liquid, polymer, semisolid, and solid material. In embodiments, the gas is atmospheric air (e.g., room air trapped inside during manufacture). In embodiments, the liquid comprises an aqueous liquid, organic liquid,

[0147] In embodiments, the liquid comprises a polymer, an aqueous solution, or an organic liquid, a mixed aqueous-organic mixture, and / or a gel. In embodiments, the encapsulated particle has an interior volume of X, and magnetically-responsive particle (or particles) have a volume of Y, where the fluid or liquid within the shell occupies up to about 100% of the difference between volumes (X- Y), or about 99%, or about 98%, or about 97%, or about 96%, or about 95%, or about 94%, or about 93%, or about 92% or about 91% or about 90%, or about 85%, or about 80%, or about 70%, or about 60%, or about 50%, or about 40%, or about 30%, or about 20%, or about 15%, or about 10%, or about 9%, or about 8%, or about 7%, or about 6%, or about 5%, or about 4%, or about 3%, or about 2%, or about 1 %, or about 0.5%, or about 0.2%, or about 0.1 %, or about 0.01 %, or about 0.001 % of the difference between the volumes.

[0148] In embodiments, the encapsulated magnetochromic particle comprises a liquid having one or more additives, preservatives, anti-oxidants, lubricants, emulsifiers, stabilizers, thickeners, anti-foaming agents, humectants, anti-bacterial agents, anti-caking agents, inorganic salts, pH adjusters, pH buffers, and rheology modifiers. In embodiments, the lubricant comprises one or more of mineral oil, synthetic oil, grease,a silicone-based lubricant, a graphite-based lubricant, molybdenum disulfide, vegetable oils, and Teflonbased lubricants. In embodiments, magnetochromic particles are manufactured with one or more materials inside the shell to alter the optical properties and / or modulate the friction of movement of the magnetically- responsive particle.

[0149] In embodiments, methods herein include encapsulating multiple magnetochromic particles within a single encapsulant. In embodiments, the method includes placing about or at least about 1 , about or at least about 2, about or at least about 3, about or at least about 4, about or at least about 5, about or at least about 6, about or at least about 7, about or at least about 8, about or at least about 9, about or at least about10, about or at least about 12, about or at least about 14, about or at least about 16, about or at least about18, about or at least about 20, about or at least about 25, about or at least about 30, about or at least about35, about or at least about 40, about or at least about 45, about or at least about 50, about or at least about100, about or at least about 200, or more than 200 magnetochromic particles, including numbers of core particles therebetween, within a single encapsulant. Likewise, in embodiments, the magnetochromic particles are arranged in about or at least about 1 , about or at least about 2, about or at least about 3, about or at least about 4, about or at least about 5, about or at least about 6, about or at least about 7, about or at least about 8, about or at least about 9, or about or at least about 10 layers within encapsulant to generate larger particles, having move complex optical properties. In embodiments with 2 or more core particles, the particles are equivalent in size. In embodiments with 2 or more magnetochromic particles, the particles are monodisperse. In embodiments with 2 or more magnetochromic particles, the particles are differently-sized. In embodiments with 3 or more magnetochromic particles, the particles are polydisperse. In embodiments, magnetochromic particles, in any arrangements or sets as described herein, are polydisperse. In embodiments with 3 or more magnetochromic particles, there are two or more sets of monodisperse particles.

[0150] In embodiments, in methods producing encapsulated particles having two or more magnetochromic core particles, the magnetochromic particles each exhibit substantially equivalent optical properties (and optical property changes in response to stimuli).

[0151] In embodiments, in methods producing encapsulated particles having two or more magnetochromic particles, the particles each exhibit distinct optical properties. In such embodiments, methods herein include producing two or more difference pluralities of magnetochromic particles that differ in the amount / type of force needed for optical change, the optical change exhibited, the relaxation time, etc.

[0152] In embodiments, methods herein comprise using one or more coating materials and / or a chemical functionalization covering at least a portion of the outer shell. In embodiments, the one or more coating materials is or comprises a swellable material covering the core particle.

[0153] In embodiments, the outer shell comprises layer-by-layer assembled materials. In embodiments, the outer shell is formed by etching and / or the use of swellable materials.

[0154] In embodiments, the outer shell comprises layer-by-layer assembled materials. In embodiments, the outer shell is formed by etching and / or the use of swellable materials. In embodiments, swellable materials include polymers which increase or decrease in volume as a function of changing conditions, such as pH, temperature, metal salt concentration, etc. For example, in embodiments, swellable polymers can increase in volume or decrease in volume by decreasing pH or increasing pH, increase temperature or decreasing temperature, or by increasing metal ion (metal salt) concentration or decreasing metal ion concentration. In embodiments, swellable polymers are used to create an encapsulated Janus particle (JP)- based magnetochromic particles. In embodiments, this process does not involve removal of a sacrificial layer. For example, in embodiments, a swellable material is applied to the core particle, the outer shell is encapsulated around the swellable material, followed by changing one or more of the pH, temperature, and / or metal ion concentrations to control the extent of swelling / shrinking to generate a void space between the magnetochromic particle and shell.

[0155] In embodiments, methods herein comprise forming encapsulated magnetochromic Janus particles using a reversibly-swellable polymer shell. In embodiments, the magnetochromic particle is coated with a polymer coating which is expanded. In embodiments, a shell is grown around the expanded polymer. In embodiments, the magnetochromic core particle is composed of a swellable material, which is subjected to a condition to cause swelling, which then a shell coating is disposed around the swelled core particle. In embodiments, contraction of the magnetochromic core particle creates a void space between the core and the outer shell, thereby encapsulating the magnetochromic core particle. In embodiments, non-limiting examples of materials include polymethylmethacrylate polymer or methacrylate-based silica particles which are coated with a swellable methacrylic acid-based polymer. In embodiments, swelling is controlled by metal ion concentration, pH, and / or temperature. In embodiments, swelling is induced with increasing metal ion concentration, pH, and / or temperature. In embodiments, swelling is induced with decreasing metal ion concentration, pH, and / or temperature.Opticallv-Active Agents and Coating Particles

[0156] In embodiments, the terms “optically active agent,” or “colorant,” or “colored material” are used interchangeably and refer to a chemical entity that has an optical property, including absorbing, scattering (including Raman scattering), transmitting, refracting, reflecting, dispersing, polarizing, fluorescing, luminescing, and / or phosphorescing, any wavelength, or range of wavelengths, of radiation. In embodiments, the at least one optically active agent or colorant possesses an extinction in the electromagnetic spectrum between the x-ray / ultraviolet region (wavelengths >10 nm) and microwave / radio region (<10 cm). In embodiments, wavelength, or range of wavelengths, of radiation are in the visible spectrum, i.e., from about 380 nm to about 800 nm in wavelength. In embodiments, an optical agent or colorant possesses a color, brightness, fluorescence, reflectance, etc., that can be detected by human vision. In embodiments, the optically active agent or colorant has an extinction in the visible region of the electromagnetic spectrum, or a color of one or more of white, black, red, orange, yellow, green, blue, indigo, violet, and variations of hue, shade, and intensity therebetween.

[0157] In embodiments, any optically-active agent, as used herein, comprises one or more of a dye, pigment, stain, fluorophore, chromophore, metal, metal salt, metal oxide, metal nitride, inorganic material, silica, organic material, organic polymer, inorganic polymer, biological polymer, synthetic polymer, and combinations thereof.

[0158] In embodiments, at least the first optically active agent and / or at least the second optically active agent comprise a single colorant, 2 colorants, 3 colorants, 4 colorants, 5 colorants, 6 colorants, 7 colorants, 8 colorants, 9 colorants, or 10 or more colorants.

[0159] In embodiments, methods herein include coating at least a portion of a surface of the magnetically-responsive particles and / or the outer shell with one or more optically active agent. The coating, in embodiments, can include painting, spraying or spray coating, sputtering, evaporation coating, glow discharging, or otherwise applying at least one optically active agent onto at least a portion of the external surface area of the one or more magnetically-responsive particles. In embodiments, the application is confined to a specific surface area of each particle, which is controlled via the application of a magnetic field and / or a mask substrate such that each particle is coating in a substantially identical manner. In embodiments, methods include formulating the optically active agent for use prior to application, for example where the optically active agent needs re-suspended, dissolved, or otherwise solvated into one or more solvents. In embodiments, the solvent is selected based upon the particle material (e.g., polymer, etc.), themagnetic material (e.g., type of metal, metal oxide, polymer, etc.), or the desired fluid properties (e.g., viscosity, spray rate, drying time, etc.).

[0160] In embodiments, and in reference to Figs. 9A-9E, magnetically-responsive particles are magnetically-orientable such that the reproducibility of manufacturing between particle batches is maintained. In embodiments, and in reference to Fig. 9A, magnetic Janus particles suspended in solution are deposited onto a 2-D array on a planar substrate containing features (circular pores) designed to fit a single particle each (e.g., as shown in Fig. 9B). In embodiments, and in reference to Fig. 9C, depicts the use of a magnet to orient the particles such that all magnetic materials are facing the magnet (although any orientation is possible). In embodiments, and in reference to Fig. 9D, this enables deposition of an optical agent (e.g., colored material shown as gray) onto the surface of the 2-D array such that the magnetically-responsive particle are coated in a substantially identical manner. In embodiments, and in reference to Fig. 9E, the final coated particles are formulated into solution.

[0161] In embodiments, at least the first optically active agent and / or at least the second optically active agent comprise one or more dyes. In embodiments, the dye is an organic or inorganic dye. In embodiments, the dye comprises one or more of Rhodamine B, Congo Red, Crystal Violet, Methylene Blue, Acridine Orange, Nile Red, Malachite Green, Eosin Y, Cresol Red, Fluorescein, and Indigo.

[0162] In embodiments, the one or more colorant comprises a pigment. In embodiments, the pigment comprises a water-soluble pigment. In embodiments, the water-soluble pigment is one or more of anthocyanin, anthraquinone, carotenoid, violacein, melanin, pyocyanin, prodiginines, asperversin, benzoquinone, anthraquinone, and derivatives thereof.

[0163] In embodiments, the pigment comprises one or more of Titanium White (PW6), Zinc White (PW4), Carbon Black (PBk7), Mars Black (P Bk11 ), Iron Oxide Red (PR101 ), Cadmium Red (PR108), Alizarin Crimson (PR83), Cadmium Orange (PO20), Cadmium Yellow (PY35), Lemon Yellow (PY3), Chromium Green Oxide (PG17), Phthalo Green (PG7), Ultramarine Blue (PB29), Cobalt Blue (PB28), Cerulean Blue (PB35), Prussian Blue (PB27), Burnt Sienna (PBr7), Raw Umber (PBr7), Raw Sienna (PBr7), and Yellow Ochre (PY43).

[0164] In embodiments, the pigment is an organic pigment. In embodiments, the pigment is an inorganic pigment.

[0165] In embodiments, the organic pigment or inorganic pigment comprises a white pigment. In embodiments, the white pigment is one or more of lead white (2PbCO3'Pb(OH)2), kaolin, silica (SiCh), titanium dioxide (TiO2 / rutile and anatase), zinc oxide (ZnO), zinc sulfide (ZnS), and / or lithopone (ZnS + BaSC ).

[0166] In embodiments, the organic pigment or inorganic pigment comprises a black pigment. In embodiments, black pigment is one or more of coal (charcoal), groutite (a-MnOOH), manganite (y-MnOOH), hausmannite (I C ), carbon black, iron oxide black (FesCU), and / or spinel black (CuCtoC ).

[0167] In embodiments, wherein the organic pigment or inorganic pigment comprise a colored pigment.

[0168] In embodiments, the colored pigment comprises a yellow pigment. In embodiments, the yellow pigment comprises one or more of yellow ochre (a-FeOOH), auric pigment (AS2S3), lead ochre (PbO), lead tin yellow (Pb2SnO4, PbSn2SiO?), Naples yellow (Pb(SbO3)2), zinc yellow (Zn2CrCU), Indian yellow (C19H16O10), iron oxide yellow (a-FeOOH), chromium titanium yellow ((Ti,Cr,Sb)C>2), nickel titanium yellow ((Ti, Ni,Sb)C>2), lead yellow (PbCrCh), cadmium yellow (CdS), bismuth yellow (BiVC ).

[0169] In embodiments, the colored pigment comprises a red pigment. In embodiments, the red pigment comprises one or more of red ocher (a-Fe2O3), Terra di Siena (a-Fe2C>3), vermilion (HgS), lead red (PbsCU), alizarin madder varnish, alizarin red (C14H8O4), iron oxide red (a-Fe2O3), molybdate red (Pb(Cr,S,Mo)O4), cadmium red (Cd(S,Se)).

[0170] In embodiments, the colored pigment comprises a green pigment. In embodiments, the green pigment comprises one or more of green earth (Fe silicates), Schweinfurt green (C4H6AS6CU4O16), chromium oxide green (C Os), chromium oxide hydrate green (CrOOH), cobalt green (CtoTiCh).

[0171] In embodiments, the colored pigment comprises a blue pigment. In embodiments, the blue pigment comprises one or more of lazurite (lapis lazuli), Egyptian blue (CaCuSi40io), azurite (2CUCO3-CU(OH)2), malachite (CuCO3'Cu(OH)2), cobalt blue (COAI2O4), ultramarine blue (Na6AI6Si6O24(NaSn)), iron blue (K[FelllFell(CN)6] xH2O).

[0172] In embodiments, the colored pigment comprises a brown pigment. In embodiments, the brown pigment comprises one or more of burnt umber (Fe2O3-xMnC>2), brown ocher (a-Fe2O3 + Mn oxides), limonite (mixture of different Fe oxides).

[0173] In embodiments, the pigment is one or more of an oxide or oxide hydroxide pigment (TiO2, ZnO, a-Fe2O3, a-FeOOH, y-Fe2O3, FesO4, Cr20s, CrOOH, PbO, PB3O4, Mn3O4, -MnOOH, Sb2O3), a complex oxidepigment (COAI2O4, CuC C , Co2TiO4, (Ti,Ni,Sb)02, (Ti,Cr,Sb)02), a carbonate hydroxide pigment (2PbCO3-Pb(OH)2, 2CUCO3-CU(OH)2, CUCO3-CU(OH)2), a sulfide / selenide pigment (ZnS, CdS, Cd(S,Se), CdSe, y-Ce2S3, HgS, AS2S3), a chromate / molybdate pigment (PbCrCH, Pb(Cr,S)O4, Pb(Cr,S,Mo)CU, ZnCrCU, BaCrO4, SrCrC ), a vanadate pigment (BiVC , 4BiVO4'3Bi2MoOe), a stannate pigment (Pb2SnO4, PbSn2SiO / , Co2SnO4, CoSnOs), a phosphate pigment (Co3(PO4)2), an antimonate pigment (Pb(SbO3)2), an arsenate pigment (Cu(AsO3)2), an ultramarine pigment (NaeAleSieCMNaSn)), a hexacyanidoferrate / hexacyanoferrate pigment (K[FelllFell(CN)6]-xH2O (x = 14-16)), an oxonitride pigment (CaTaChN, LaTaON2), an elemental-based pigment (C, Al, Cu, Cu / Zn, Au), a spinel-based pigment, and / or a rutile-based metal pigment.

[0174] In embodiments, methods herein include manufacturing particles which exbibit a wide range of optical effect, including those using “special pigments,” which provide complicated optical effects. In embodiments, the inorganic pigment is one or more of a transparent effect pigment, goniochromatic pigments, pearlescent pigment, metallic pigment, interference pigment, metallic effect pigment, fluorescent pigment, luminescent pigment, phosphorescent pigment, magnetic pigment, and anticorrosive pigment.

[0175] In embodiments, the metallic pigment comprises one or more of aluminum, bronze, and copper metallic pigment.

[0176] In embodiments, the pearlescent pigment comprises one or more of mica, titanium dioxide, and bismuth oxychloride.

[0177] In embodiments, the fluorescent pigment comprises one or more fluorescent dye and pigment comprising a fluorescent mineral.

[0178] In embodiments, the phosphorescent pigment comprises zinc sulfide and / or strontium aluminate.

[0179] In embodiments, the interference pigment comprises titanium dioxide-coated mica and / or aluminum oxide-coated mica.

[0180] In embodiments, the one or more optically active agents comprise an anisotropic particle. In embodiments, the anisotropic particle comprises a nanoparticle of the one or more metals, optionally comprising a nanorod of one or more of gold (Au), silver (Au), and aluminum (Al).

[0181] In embodiments, the one or more optically active agents comprises a plasmonic material. In embodiments, the plasmonic material comprises a pigment, particle, foil, and / or film. In embodiments, the film comprises a polymer-film loaded with noble metal nanoparticles.

[0182] In embodiments, the goniochromatic pigment comprises aluminum coated with magnesium fluoride embedded in chromium.Coating Materials

[0183] In embodiments, additional elements are added during methods of manufacturing to modify the functionality of the magnetochromic particle. In embodiments, the method includes coating the one or more magnetically-responsive optically-variable particles with one or more coating materials. In embodiments, a coating material is a fine layer of powder, paint, oil, etc. that is used to alter the surface properties, including the friction, coloration, etc.

[0184] In embodiments, and in reference to Figs. 10A-10E, coating materials are used as sacrificial layers that are removed to ensure equal spacing between the shell from the encapsulated magnetically- responsive particle such that enough space is available for movement of the particle. In embodiments, and in reference to Figs. 10A-10B a magnetically-responsive particle substantially corresponding to the spherical particle of Fig. 1 A is suspended in solution. In embodiments, and in reference to Fig. 10C depicts the particle of Fig. 10B with one or more coating materials, where the coating material is added while the particles are suspended in solution, or after removal from solution. In embodiments, and in reference to Fig. 10D, the coated particle is encapsulated in a shell. In embodiments, and in reference to Fig. 10E, one or more of the coating materials removed after shell formation such that the volume previously occupied by the coating material is now vacant.

[0185] In embodiments, the coating material is thick or thin (e.g., relative to the dimensions of the particle), smooth or rough, conformal or non-conformal, porous or non-porous, comprises a single layer or multiple layers, is optically transmissive or partially transmissive, and / or comprises one or more organic substances, one or more inorganic substances, one or more biological substances, or any combination of organic, inorganic, and / or biological substances.

[0186] In embodiments, the coating material is used to alter the impact of friction (e.g., used to mitigate friction or increase friction) on the movement of the magnetically-responsive particle within the shell. In embodiments, coating materials include lubricants, surface treatments and / or coatings (e.g., TEFLON, polytetrafluoroethylene (PTFE), hydroxylated self-assembled monolayers, vitreous enamel, etc.), polishing (e.g., with ceria (cerium oxide), etc.), materials with lower coefficients of friction relative to the shell and / or core particle (e.g., ceramics, anodized metals, silica, etc.).

[0187] In embodiments, the coating material includes an additive, reagent, layer, and / or surface modification is incorporated into the particle to reduce friction between the one or more particle and the inner surface of the outer shell. In embodiments, this enables greater freedom of movement in response to a magnetic field. In embodiments, the coating material used to reduce friction include but are not limited to graphene, graphite and other carbon materials, polytetrafluoroethylene, molybdenum disulfide, silicon- containing molecules and polymers, polyethylene glycol, water, non-aqueous solvents, mineral oil lubricants, synthetic lubricants, nanoparticles with a high degree of hardness, and components of grease.

[0188] In embodiments, one or more coating materials are associated with the inner surface of the outer shell of the particle. In embodiments, the substances are associated by electrostatics, adsorption, or by non- covalent or covalent chemical bonding.

[0189] In embodiments, one or more of the material used to make the particle (e.g., polymeric material and / or magnetic material), the optically active agents, or the encapsulant (e.g., outer shell) are functionalized with pendant functional groups. In embodiments, one or more of these components are treated to be surface functionalized with pendant functional groups. In embodiments, the pendant functional groups comprise alcohols, ethers, aldehydes, ketones, carboxylates, amides, esters, amines, alkyl amines, dialkyl amines, cyanides, isocyanides, thiethers, sulfhydryls, or thioesters. In embodiments, methods herein include functionalizing particles to confer the desired surface chemical properties to the outer shell and / or magnetochromic core particle. In embodiments, methods include functionalizing particles (e.g., silica shell and / or magnetochromic core) are functionalized to be more hydrophilic or hydrophobic, for example by treatment with alkyl groups, hydrocarbons (e.g., C12), PEG-silanes, etc., for instance as described in Bjbrkegren et al., “Hydrophilic and hydrophobic modifications of colloidal silica particles for Pickering emulsions,” Journal of Colloid and Interface Science, Volume 487 (2017): pp. 250-257, the entire contents of which are incorporated herein by reference. In embodiments, the outer shell of the magnetochromic particle is functionalized to make the particles more hydrophobic. In embodiments, the outer shell of the magnetochromic particle is functionalized to make the particles more hydrophilic. In embodiments, altering the surface chemistry enables the use of microfluidics with a variety of solvents, and / or enables a variety of curing processes (e.g., UV-crosslinking, thermally-responsive curing, hardening, or crosslinking, etc.).Formulating the Magnetically-Responsive Particles and Compositions Thereof

[0190] In embodiments, methods of manufacturing particles includes formulating the particles into one or more compositions for application (e.g., applying to an object to provide magnetically-responsive optically- variable properties).

[0191] Methods of manufacturing particles herein, in embodiments, include formulating the particles into a fluid, suspension, ink, liquid film, and / or adhesive substrate, material, and / or surface. In embodiments the formulating includes selecting the appropriate fluid, liquid, ink, adhesive, etc., and admixing the magnetically-responsive particles via gentle agitation or stirring. In embodiments, the fluid, suspension, ink, liquid film, and / or adhesive substrate, material, and / or surface is selected to be suitable to be applied to an object, and / or not to interfere with the optical properties of the particles, and / or to be compatible with the materials of the particles (e.g., does not dissolve the polymers or magnetic material the particles are composed of). In embodiments, the liquid comprises one or more of an emulsifier, surfactant, solvent, viscosity modifier, salt, rheological agent, anti-microbial agent, pH adjuster, buffer, suspending agent, biological polymer, synthetic polymer, and organic molecule.

[0192] In embodiments, formulating includes admixing the magnetochromic particles in a mass per volume, for example at about or at least about 0.001 mg / mL, about or at least about 0.01 mg / mL, about or at least about 0.1 mg / mL, about or at least about 1.0 mg / mL, about or at least about 10 mg / mL, about or at least about 50 mg / mL, about or at least about 100 mg / mL, about or at least about 150 mg / mL, about or at least about 200 mg / mL, about or at least about 250 mg / mL, about or at least about 300 mg / mL, about or at least about 350 mg / mL, or about or at least about 400 mg / mL or more.

[0193] In embodiments, formulating includes admixing the magnetochromic particles in a concentration of about or less than about 0.001% (w / v), about or less than about 0.1% (w / v), about or less than about 0.5% (w / v), about or less than about 1 % (w / v), about or less than about 2% (w / v), about or less than about 3% (w / v), about or less than about 4% (w / v), about or less than about 5% (w / v), about or less than about 6% (w / v), about or less than about 7% (w / v), about or less than about 8% (w / v), about or less than about 9% (w / v), about or less than about 10% (w / v), about or less than about 12% (w / v), about or less than about 14% (w / v), about or less than about 16% (w / v), about or less than about 18% (w / v), about or less than about 20% (w / v), about or less than about 25% (w / v), about or less than about 30% (w / v), about or less than about 35% (w / v), about or less than about 40% (w / v), about or less than about 50% (w / v), about or less than about 60% (w / v), or about or less than about 70% (w / v).

[0194] In embodiments, methods of manufacturing particles herein includes formulating the one or more magnetically-responsive optically-variable particles by applying and / or arranging them onto a substrate. In embodiments, the substrate includes applying and / or adhering to a surface of a foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material.

[0195] Methods for immobilizing binding molecules onto surfaces and / or applying magnetochromic particles to surfaces include, for example, a variety of surface chemical treatment and attachment chemistries, as described in Wang & Jin, 2004; Vashist, 2012; Vashist, et al., 2014; U.S. Patent No. 7,577,470; and U.S. Patent No. 7,813,780, the entirety of each of which is hereby incorporated by reference.

[0196] For example, in embodiments and in reference to Figs. 11 A-11C encapsulated magnetochromic particles of the present disclosure are immobilized on a surface to imbue the surface with magnetically- responsive optically-variable properties. In embodiments and in reference to Fig. 11 A, the particles are arranged in a 2-D array, with all the magnetically-responsive particles in the same orientation (e.g., such that the magnetic materials are all facing to the left). In embodiments, the shell of each particles is immobile, and is directly associated with a substrate (e.g., shown as the grey plane in contact at the bottom of each particle). In embodiments, this is achieved by gluing the outer surface of the shell to the surface. In embodiments, an observer looking down at this particle array would observe the color associated with the top hemisphere of each magnetically-responsive particle (e.g., the top-facing white hemisphere). In embodiments and in reference to Fig. 11 B, the array shifts position after applying a magnetic field, where the magnetic field is oriented from left to right, causing the particles to rotate clockwise by 180°. In embodiments, an observer would now observe the color associated with the bottom hemisphere (e.g., the cross-hatched hemisphere in Figs. 11 A-11 C). In embodiments and in reference to Fig. 11 C, after a magnetic field is applied in the opposite direction, e.g., oriented from right to left, the particles rotate counter-clockwise by 180°, where an observer once again observes the color associated with the top hemisphere.

[0197] In embodiments, formulating the substrate comprises applying the particles to a foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material, and using an adhesive, solvent, and / or by spraying the fluid, suspension, ink, liquid film, and / or adhesive substrate onto a thin film, plastic, polymer, and / or paper substrate. In embodiments, the foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material is suitable to be affixed to, or embedded in, an object. In embodiments, the formulation is performed using biotin-streptavidin linkage, click-chemistry, maleimide-based reactions, carbodiimide-based reactions, etc., to adhere the magnetochromic particles to the substrate.

[0198] In embodiments, the magnetically-responsive optically-variable particles cover a surface area of the substrate of about or less than about 1 %, about or less than about 5%, about or less than about 10%, about or less than about 15%, about or less than about 20%, about or less than about 25%, about or less than about 30%, about or less than about 35%, about or less than about 40%, about or less than about 45%, about or less than about 50%, about or less than about 55%, about or less than about 60%, about or less than about 65%, about or less than about 70%, about or less than about 75%, about or less than about 80%, about or less than about 85%, about or less than about 90%, about or less than about 95%, or about or less than about 99% of the foil, film, thin plastic, and / or paper substrate, material, and / or surface.

[0199] In embodiments, the substrate (e.g., foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material) is transparent to at least a portion of the visible electromagnetic (EM) spectrum and / or opaque. In embodiments, the substrate comprises a material of one or more of glass, sapphire, diamond, silicon, organic polymers, organic materials, biological polymers, metal oxides, quartz, plastic, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers (TPE), acrylonitrile butadiene styrene (ABS), epoxies and epoxybased photoresists, hydrogels, cyclic olefin copolymer (COC) cyclic olefin polymer (COP), poly dimethyl siloxane (PDMS), poly ether ester ketone (PEEK), polyetherimide (ULTEM) and nylon.

[0200] Methods of manufacturing particles herein, in embodiments, include formulating the magnetochromic particles into a fiber, thread, yarn, twine, and / or material thereof. In embodiments, the formulating includes spindling to form fibers, threads, yarn, twine, etc. while incorporating the particles therein, for example, using optically-transparent material, in embodiments, formulating the particles into fiber, thread, yarn, twine, and / or material thereof includes cladding and fiber draw processes similar to how fiber optic cables / fibers are made. In embodiments, the fiber, thread, yarn, and / or twine substrate, material, and / or surface is suitable to be woven into an article of clothing, a cloth, and / or a tarp.

[0201] In embodiments, formulations (e.g., compositions comprising particles) include magnetochromic particles in a number of particles per area, for example, at about or at least about 106particles / mm2, about or at least about 105particles / mm2, about or at least about 104particles / mm2, about or at least about 1,000 particles / mm2, about or at least about 100 particles / mm2, about or at least about 50 particles / mm2, about or at least about 10 particles / mm2, about or at least about 5 particles / mm2, about or at least about 1 particles / mm2or fewer, including ranges and amounts therein.

[0202] In embodiments, formulations (e.g, compositions comprising particles) include magnetochromic particles in a number of particles, for example, present in a number of particles per distance in length, for example, at about or at least about 50,000 particles / mm, about or at least about 10,000 particles / mm, about or at least about 1 ,000 particles / mm, about or at least about 500 particles / mm, about or at least about 100 particles / mm, about or at least about 50 particles / mm, about or at least about 10 particles / mm, about or at least about 5 particles / mm, about or at least about 1 particles / mm, about or at least about 0.5 particles / mm, or about or at least about 0.1 particles / mm, or fewer, including ranges and amounts therein.Kits

[0203] In aspects, described herein are kits for performing the methods of manufacture described herein, and / or kits with the intermediates of the magnetochromic particle manufacture methods for carrying out one or more sub-steps of the overall methods described herein.

[0204] In embodiments, the compositions (e.g., magnetochromic particle paper / foil, fluid, solution, suspension, fiber, thread, etc.) of the present disclosure are assembled into a kit. In embodiments, the kit comprises magnetochromic particles in one or more formulations described herein for application to one or more objects.

[0205] In embodiments, the kit comprises various sizes / types of “blank” particles and a series of optically active agents (e.g., pigments, dyes, stains, paints, etc.) that are suitable to be used to make batches of custom particles. For example, in embodiments, the kit comprises one or more sizes (e.g., diameters) of the magnetically-responsive particles and one or more colors of optically active agents, each held in a pouch, bag, vial, etc., where the appropriate magnetically-responsive particle is selected and the appropriate amount of optical agent is selected and dissolved, re-suspended, etc, such that magnetochromic particles are made.

[0206] In embodiments, the kit comprises a means for applying a magnetic field and / or a substrate to dispose the one or more magnetically-responsive particles upon. In embodiments, the means for applying a magnetic field includes a magnet, electromagnet, or other material having a magnetic quality (e.g, ferromagnetic, ferrimagnetic, antiferromagnetic, diamagnetic, paramagnetic, superparamagnetic, and / or antiferromagnetic), or otherwise capable of being used to apply a magnetic field in the range of at least about 200 gauss to about or at least about 25,000 gauss (10,000 gauss = 1 Tesla), or greater. In embodiments, the kit comprises one or more surface for particles to be disposed upon to be coated with the optically active agents, including any described herein, for example plastic, paper, thin film, metal sheets, etc. In embodiments, the kit comprises one or more masks for custom coating of the magnetochromic particles (e.g.coating with an optically active agent and / or coating material), a means for applying a magnetic field, a substrate to dispose the one or more magnetically responsive particles upon (e.g., after attachment of the magnetic material and before coating), and one or more optically active agents.

[0207] In embodiments, the kit comprises magnetic material (e.g., beads or particles) that are suspended or dissolved in a solution; or present in a pouch, vial, bag. etc., as a dry magnetic material (e.g., fine powder) suitable to be suspended or dissolved in a liquid. In embodiments, the kit comprises one or more particles that are suspended or dissolved in a solution; or present in a pouch, vial, bag. etc., as a dry particle material (e.g., fine powder) suitable to be suspended or dissolved in a liquid.

[0208] In embodiments, the kit comprises one or more materials to encapsulate the magnetochromic particles with a shell.

[0209] The kits described herein may include one or more containers housing components for performing the methods described herein and optionally instructions for use. Any of the kits described herein may further comprise components needed for performing the manufacturing methods described herein. Each component of the kits, where applicable, may be provided in liquid form (e.g., in solution, suspension, ink, paint, etc.) or in solid form, (e.g., dry powders, paper, foil, fiber, etc.). In embodiments, some of the components are reconstitutable or otherwise processible (e.g., magnetochromic particles in powder / granule form that can be resuspended in one or more solvents / fl uids to be applied to an object), for example, by the addition of a suitable solvent or other species (for example, water, ink, or paint), which may or may not be provided with the kit.

[0210] In embodiments, the kits may optionally include instructions and / or promotion for use of the components provided. As used herein, "instructions" can define a component of instruction and / or promotion, and typically involve written instructions on or associated with packaging of the disclosure. Instructions also can include any oral or electronic instructions provided in any manner such that a user will clearly recognize that the instructions are to be associated with the kit, for example, audiovisual (e.g., videotape, DVD, etc.), Internet, and / or web-based communications, etc. As used herein, "promoted" includes all methods of doing business including methods of education, engineering instruction, scientific inquiry, discovery or development, academic research, manufacturing, chemical, cosmetic, and pharmaceutical industry activity including sales, and any advertising or other promotional activity including written, oral, and electronic communication of any form, associated with the disclosure. Additionally, the kits may include other components depending on the specific application, as described herein.

[0211] The kits may have a variety of forms, such as a blister pouch, a shrink wrapped pouch, a vacuum sealable pouch, a sealable thermoformed tray, or a similar pouch or tray form, with the accessories loosely packed within the pouch, one or more tubes, containers, a box, or a bag.

[0212] Without further elaboration, it is believed that one skilled in the art can, based on the above description, utilize the present disclosure to its fullest extent. The following specific embodiments are, therefore, to be construed as merely illustrative, and not limiting of the remainder of the disclosure in anyway whatsoever.EXAMPLESExample 1: Synthesis of Ma neticallv-Responsive Qpticallv-Variable Particles Incorporating A Vapor Phase Deposition Step

[0213] Magnetic Janus yolk particles were prepared as follows: a dilute aqueous solution of ABSOLUTE MAG DBCO magnetic particles, 0.97 pm diameter (polystyrene, obtained from CD Bioparticles) was added dropwise to concentrated aqueous solution of DIAGPOLY azide poly (methyl methacrylate) (PMMA) particles, 16 pm diameter (obtained from CD Bioparticles). Using click chemistry, and ratio of magnetic particles to PMMA particles was 1 :10, the DBCO chemistry on the polystyrene magnetic particles enabled a specific 1 :1 stoichiometric reaction with the azide group on the PMMA particles such that 1 magnetic particle attached to each PMMA particle. After reaction, PMMA particles derivatized with magnetic particles (e.g., magnetically- responsive particles) were pulled to the side of the reaction vessel with an applied magnetic field (e.g., using a magnet). The unreacted PMMA particles were decanted, and pure water was added back to the reaction flask to rinse the magnetically-responsive particles. The vessel was mixed and the process of magnetic capture / decanting was repeated three times. The resulting magnetically-responsive particles were resuspended in water and sonicated to eliminate clumped particles.

[0214] Following the procedure, for example, as described in Lee et al., “Magnetically locked Janus particle clusters with orientation-dependent motion in AC electric fields,” Nanoscale, Vol. 15, (2023): pp. 16268-76, the entirety of which is incorporated herein by reference, a sub-monolayer of particles were prepared by a convective assembly-inspired method (e.g., as described further in Prevo at al., “Engineered deposition of coatings from nano- and micro-particles: A brief review of convective assembly at high volume fraction," Colloids and Surfaces A: Physicochem. Eng. Aspects, Vol. 311 , (2007): pp. 2-10, incorporated herein by reference in its entirety). 10 nm particles of Cr and 50 nm particles of Au were deposited as optically- active agents onto the particles by e-beam evaporation. Coated particles were removed from the substrateby gently scraping with a metal spatula. The coated particles were resuspended in purified water, and sonicated for 15 min.

[0215] To convert the above core particles into encapsulated particles, a resorcinol-formaldehyde polymer dissolution-regrowth approach was used, for example, as described in Zhou et al., “Formation of Resorcinol-Formaldehyde Hollow Nanoshells through a Dissolution-Reqrowth Process,” Nanoscale, Vol. 12, (2020): pp. 15460-65, which is herein incorporated by reference in its entirety. Resorcinol and formaldehyde were polymerized using a modified Stober method to form a core-shell particle. Next, the inner part of the shell was dissolved using a solvent (e.g., ethanol or tetrahydrofuran). 1 ml_ of the microfluidically-generated carbon black / titania Janus core particles were suspended in water were sonicated, and then mixed with 50 mg resorcinol and 70 pL of a formaldehyde solution, which was added to an aqueous ammonia solution (NH4OH, 160 pL, 2.8 wt%). The resulting solution was sonicated for 1 hr. at room temperature (approx. 22°C). The resulting mixture was centrifuged and redispersed in water several times. An etching solution comprising 1 mL of ethanol was added and dispersed ultrasonically, with subsequent stirring for 10 minutes. The resulting particles were collected and purified by repeated centrifugation / water resuspension cycles.Example 2: Microfluidics-Based Methods of Macineticallv-Responsive Particles

[0216] Non-spherical magnetic Janus particles similar to those shown in Fig. 7D at part (ii) were prepared using a combination of methods described in Saqib et al., “Synthesis of Anisotropic Magnetic Polymeric Janus Particles by In Situ Separation of Magnetic Nanoparticles in a Microfluidic Device”, Langmuir, 2023 Vol. 39, No. 48, (2023): pp. 17080-87; Nisisako et al., “Synthesis of Monodisperse Bicolored Janus Particles with Electrical Anisotropy Using a Microfluidic Co-Flow System,” Adv. Mater. (2006), Vol. 18, 2006: pp. 1152-56, and Xu et al., “Generation of Monodisperse Microparticles using Microfluidics: Control over Size, Shape, and Composition”, Angew. Chem. Int. Ed. (2005) 44, 724 -728; and Miralles et al., “A Review of Heating and Temperature Control in Microfluidic Systems: Techniques and Applications”, Diagnostics (2013), 3, 33-67, and Issadore et al., “Microwave dielectric heating of drops in microfluidic devices”, Lab on a Chip (2009), 9 (12), 1701 , each of which is herein incorporated by reference in their entirety.

[0217] Spherical Janus particles were made using the methods in Nisisako et al., where magnetic nanoparticles were added to both parts of the droplet precursors. After droplet formation, the nascent particles were elongated into ellipsoidal particles by channel narrowing according to Xu et al. Subsequently, following the protocols in Saqib et al., the magnetic particles were concentrated to one side of the ellipsoid, where themagnet was positioned above the plane of the microfluidic device channel to enable collection of magnetic particles along the Janus interface. Subsequent on-chip microwave-based thermal treatment according to Miralles etal. and Issadore etal. was used to cure the particles and lock them in shape, generating a magnetic dipole.Example 3: Swellable Janus particle (JP)-based macinetochromic synthesis

[0218] A swellable magnetic Janus particle was synthesized by depositing a swellable polymer network around 4 pm seed particles composed of Fe / silica prepared by metal evaporation process. To grow a pH- responsive swellable polymer around 4 pm magnetic Janus seeds, 5 mg of the seed particles were dispersed in 40 mL acetonitrile. Triton X-100 was added to the dispersion at approx. 0.84 mM concentration. The dispersion was transferred to a flask equipped with a condenser. The dispersion was stirred, heated to 70°C and purged with nitrogen for 30 min. A pH-responsive monomer mixture composed of 0.280 M methacrylic acid, 0.280 M methyl methacrylate, and 0.020 M Ethylene glycol dimethacrylate was prepared and added to the flask. The mixture was equilibrated for 10 min. The polymerization was initiated by adding 1 mM azobisisobutyronitrile and allowed to proceed for 4.5 hrs. The reaction was quenched in water or an ice bath. The resulting product was thoroughly purified by centrifugation, with washing steps with acetonitrile, ethanol, and water. The purified particles were resuspended in water. The final dispersion exhibited strong pH- responsive swellability. To trigger the swelling, the solution pH was increased to at or above the pka of the swellable polymer using a buffer or NaOH solution. As shown in the optical microscope image of Fig. 15, a transparent swollen spherical layer was observed around each individual magnetic Janus particle. The images demonstrated, inter alia, that swellable materials (e.g., in response to pH, metal ion concentration, temperature, etc.) are usable to generate magnetochromic particles to, for example, control formation of the void space and the shell layer for encapsulation.DEFINITIONS

[0219] The following definitions are used in connection with the disclosure disclosed herein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of skill in the art to which this disclosure belongs.

[0220] As used herein, “a,” “an,” or “the” can mean one or more than one.

[0221] Further, the term “about” when used in connection with a referenced numeric indication means the referenced numeric indication plus or minus up to and including 10% of that referenced numeric indication. For example, the language “about 50” covers the range of 45 to 55.

[0222] In embodiments, the terms “at least one” and “one or more” are used interchangeably.

[0223] As referred to herein, all compositional percentages are by weight of the total composition, unless otherwise specified. As used herein, the word “include,” and its variants, is intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the compositions and methods of this technology. Similarly, the terms “can” and “may” and their variants are intended to be non-limiting, such that recitation that an embodiment can or may comprise certain elements or features does not exclude other embodiments of the present technology that do not contain those elements or features.

[0224] Although the open-ended term “comprising,” as a synonym of terms such as including, containing, or having, is used herein to describe and claim the disclosure, the present disclosure, or embodiments thereof, may alternatively be described using alternative terms such as “consisting of” or “consisting essentially of.”

[0225] In embodiments, as used herein, the words “preferred” and “preferably” refer to embodiments of the technology that afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the technology.

[0226] In embodiments, the disclosure is directed to the following embodiments:

[0227] Embodiment 1. A method of manufacturing one or more magnetically-responsive optically- variable particles, the method comprising providing a magnetic material, providing one or more particles, attaching the magnetic material to the one or more particles to generate one or more magnetically-responsive particles, applying a first magnetic field to the one or more particles to separate the one or more magnetically- responsive particles from the one or more particles that did not attach magnetic material, disposing the one or more magnetically-responsive particles onto a surface to generate a 2-dimensional array of the one or more magnetically-responsive particles, applying a second magnetic field to the one or more magnetically- responsive particles to orient the one or more magnetically-responsive particles on the surface such that anequivalent portion of the surface area of each of the one or more magnetically-responsive particles is exposed relative to one another within the 2-dimensional array, and coating at least a portion of the exposed surface area of the one or more magnetically-responsive particles with at least a first optically active agent to generate one or more magnetically-responsive optically-variable particles.

[0228] Embodiment 2. The method of embodiment 1 , wherein providing the one or more particles comprises generating the one or more particles.

[0229] Embodiment 3. The method of embodiment 2, wherein generating the particles comprises one or more of evaporation, chemical or physical self-assembly, droplet-based microfluidics, polymerization (ultraviolet polymerization), adsorption, coacervation, mixing, and extrusion.

[0230] Embodiment 4. The method of embodiment 3, wherein generating the particles comprises droplet-based microfluidics and thermal treatment.

[0231] Embodiment 5. The method of any one of embodiments 2-4, wherein generating the particles comprising forming Janus particles.

[0232] Embodiment 6. The method of any one of the preceding embodiments, wherein attaching further comprises a click-chemistry reaction to adhere the magnetic material to the one or more particles.

[0233] Embodiment 7. The method of embodiment 6, wherein the click-chemistry reaction comprises one or more of azide-alkyne cycloaddition, thiol-click reaction (thiol-ene, thiol-yne, thiol-isocyante), Diels- Alder reaction, nitrile oxide cycloaddition, tetrazole cycloaddition, oxime formation, and 1 ,3-dipolar azidealkyne cycloaddition (CuAAC).

[0234] Embodiment 8. The method of any one of the preceding embodiments, wherein attaching further comprises microfluidics to adhere the magnetic material to the one or more particles.

[0235] Embodiment 9. The method of any one of the preceding embodiments, wherein the one or more particles and / or one or more magnetically-responsive particles and / or one or more magnetically-responsive optically-variable particles comprises a dimension of about or at least about 10 nm, about or at least 20 nm, about or at least about 30 nm, about or at least about 40 nm, about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm,about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or at least about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm, about or at least about 2 pm, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm, about or at least about 200 pm, about or at least about 300 pm, about or at least about 400 pm, about or at least about 500 pm, or about or at least about 1000 pm.

[0236] Embodiment 10. The method of any one of the preceding embodiments, wherein the magnetic material comprises one or more of magnetic beads and magnetic particles.

[0237] Embodiment 11. The method of embodiment 10, wherein the magnetic beads and magnetic particles are smaller in dimension than the one or more particles.

[0238] Embodiment 12. The method of any one of the preceding embodiments, wherein the magnetic material is ferromagnetic, ferrimagnetic, antiferromagnetic, diamagnetic, paramagnetic, superparamagnetic, and / or antiferromagnetic.

[0239] Embodiment 13. The method of any one of the preceding embodiments, wherein the magnetic material comprises one or more of an inorganic, organic, carbon-based, or biomolecule-based magnetic material.

[0240] Embodiment 14. The method of embodiment 13, wherein the magnetic material comprises one or more of iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), manganese (Mn), chromium (Cr), samarium (Sm), alloys or oxides thereof; alloys, intermetallic, and / or oxides of Fe, Co, Ni, Zn, Mn, Sm; oxides are of iron, Fe2O3, FeO, and / or FesO4; ferrite material and / or doped materials of Co, Ni, Zn, and / or Mn:FexOy, and / or magnetitetetracyanoethylene (TCNE) salts, [Fe^sMes^+ITCNE]--, Li|TCNE], [MnllTPP][TCNE]* (TPP = tetraphenylporphyrin), [Fell(TCNE)(NCMe)2][FelllCl4], Mnll(TCNE)l(OH2), Mnll(TCNE)[C4(CN)8]i / 2, Fe(TCNE)[C4(CN)s]i / 2, Mnll(TCNE)3 / 2(l3)i / 2, VII|TCNE]x (x » 2), C7H5CIN3Se4, magnetic organic polymers, and polymer-bonded magnets.

[0241] Embodiment 15. The method of embodiment 14, wherein the magnetic material comprises magnetic iron oxide nanoparticles embedded in polyethylene glycol) diacrylate.

[0242] Embodiment 16. The method of any one of the preceding embodiments, wherein attaching the magnetic material is performed in a 1 :1 stoichiometric ratio and each particle comprises magnetic material at substantially one location.

[0243] Embodiment 17. The method of any one of the preceding embodiments, wherein disposing the one or more magnetically-responsive particles onto the surface comprises spraying, evaporating, or blotting the particles onto the surface.

[0244] Embodiment 18. The method of any one of the preceding embodiments, wherein the surface comprises a substrate composed of one or more of thin film, plastic, polymer, paper, glass, sapphire, diamond, silicon, organic polymer, organic material, biological polymer, metal oxide, quartz, plastic, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers (TPE), acrylonitrile butadiene styrene (ABS), epoxies and epoxybased photoresists, hydrogels, cyclic olefin copolymer (COC) cyclic olefin polymer (COP), poly dimethyl siloxane (PDMS), poly ether ester ketone (PEEK), polyetherimide (ULTEM), and nylon.

[0245] Embodiment 19. The method of any one of the preceding embodiments, wherein the surface comprises one or more detents, indentations, or markers, which enable the one or more magnetically- responsive particles to be disposed in the 2-dimensional array.

[0246] Embodiment 20. The method of any one of the preceding embodiments, wherein coating comprises spraying, sputtering, painting, glow discharging, or otherwise applying at least one optically active agent onto at least a portion of the external surface area of the one or more magnetically-responsive particles.

[0247] Embodiment 21. The method of any one of the preceding embodiments, further comprising applying a third magnetic field to the one or more magnetically-responsive optically-variable particles to reorient the one or more magnetically-responsive optically-variable particles such that a different portion of the surface area of each is exposed, and coating at least a portion of the different portion of the surface area with at least a second optically active agent.

[0248] Embodiment 22. The method of embodiment 21, wherein the one or more magnetically- responsive optically-variable particles are re-oriented substantially 180° such that an opposite surface is exposed.

[0249] Embodiment 23. The method of embodiment 21 or 22, wherein the second optically active agent is distinct from the first optically active agent.

[0250] Embodiment 24. The method of any one of the preceding embodiments, further comprising encapsulating the magnetically-responsive particles in an outer shell.

[0251] Embodiment 25. The method of embodiment 24, wherein encapsulating the magnetically- responsive particles in an outer shell comprises performing one or more of interfacial polymerization, in situ polymerization, coacervation, layer-by-layer growth, adsorption, sol-gel encapsulation, suspension crosslinking, lyophilization, spay drying, co-extrusion, fluidized bed spray coating, and phase inversion precipitation.

[0252] Embodiment 26. The method of embodiment 24 or 25, wherein the outer shell is optically transparent to at least a portion of electromagnetic radiation between frequencies of about 10 nm to about 10 cm.

[0253] Embodiment 27. The method of any one of embodiments 24-26, wherein the outer shell comprises one or more materials.

[0254] Embodiment 28. The method of any one of embodiments 24-27, wherein the outer shell comprises one or more layers.

[0255] Embodiment 29. The method of any one of embodiments 24-28, wherein the outer shell comprises at least a portion that is opaque.

[0256] Embodiment 30. The method of any one of embodiments 24-29, wherein the outer shell comprises a single, uniform thickness and / or varying thicknesses.

[0257] Embodiment 31. The method of any one of embodiments 24-30, wherein the outer shell is configured to filter or select for a wavelength or ranges of wavelengths of radiation.

[0258] Embodiment 32. The method of any one of embodiments 24-31, wherein the outer shell is configured to transmit a percentage of electromagnetic radiation of about or at least about 100%, about or at least about 99%, about or at least about 98%, about or at least about 97%, about or at least about 96%, about or at least about 95%, about or at least about 94%, about or at least about 93%, about or at least about 92%, about or at least about 91 %, about or at least about 90%, about or at least about 85%, about or at least about 80%, about or at least about 75%, about or at least about 70%, about or at least about 65%, about or at least about 60%, about or at least about 55%, about or at least about 50%, about or at least about 40%, about or at least about 30%, about or at least about 20%, about or at least about 10%, about or at least about 5%, about or at least about 4%, about or at least about 3%, about or at least about 2%, about or at leastabout 1 %, about or at least about 0.5%, about or at least about 0.4%, about or at least about 0.3%, about or at least about 0.2%, about or at least about 0.1%, about or at least about 0.05%, about or at least about 0.04%, about or at least about 0.03%, about or at least about 0.02%, about or at least about 0.01 %, about or at least about 0.005%, or about or at least about 0.001 %, relative to the intensity or amount of electromagnetic radiation that impinges on the outer shell.

[0259] Embodiment 33. The method of any one of embodiments 24-32, wherein the outer shell comprises one or more inorganic materials.

[0260] Embodiment 34. The method of any one of embodiments 24-33, wherein the one or more inorganic materials comprise one or more of alumina, silica, titania, silicon nitride, zirconia, copper oxide, iron oxide, cobalt oxide, silver, gold, aluminum, copper, tin oxide, nickel oxide, lead oxide, glass, quartz, sapphire, inorganic glasses, diamond, diamond-like materials, zinc oxide, and manganese oxide.

[0261] Embodiment 35. The method of any one of embodiments 24-31 , wherein the outer shell is porous and / or discontinuous.

[0262] Embodiment 36. The method of embodiment 35, wherein the pores and / or discontinuities comprise about or up to about 0.1%, about or up to about 1 %, about or up to about 10%, or about or up to about 50% or more of a total surface area of the outer shell.

[0263] Embodiment 37. The method of any one of embodiment 24-34, wherein the outer shell fully encapsulates the one or more magnetically-responsive optically-variable particles, resulting in a bounded internal volume.

[0264] Embodiment 38. The method of embodiment 37, further comprising filling the bounded internal volume with one or more of a gas, liquid, polymer, semisolid, and solid material.

[0265] Embodiment 39. The method of embodiment 38, wherein the gas is atmospheric air.

[0266] Embodiment 40. The method of embodiment 38, wherein the liquid comprises an aqueous liquid, organic liquid, a mixed aqueous-organic mixture, a polymer, and / or a gel.

[0267] Embodiment 41. The method of embodiment 38, wherein liquid comprises one or more additives, preservatives, anti-oxidants, lubricants, emulsifiers, stabilizers, thickeners, anti-foaming agents, humectants, anti-bacterial agents, anti-caking agents, inorganic salts, pH adjusters, pH buffers, and rheology modifiers.

[0268] Embodiment 42. The method of embodiment 41 , wherein the lubricant comprises one or more of mineral oil, synthetic oil, grease, a silicone-based lubricant, a graphite-based lubricant, molybdenum disulfide, vegetable oils, and Teflon-based lubricants.

[0269] Embodiment 43. The method of any one of embodiments 38-42, wherein the one or more gas, liquid, polymer, semisolid, and solid material occupies about or up to about 100%, about or up to about 99%, about or up to about 97%, about or up to about 96%, about or up to about 95%, about or up to about 94%, about or up to about 93%, about or up to about 92% about or up to about 91 % about or up to about 90%, about or up to about 85%, about or up to about 80%, about or up to about 70%, about or up to about 60%, about or up to about 50%, about or up to about 40%, about or up to about 30%, about or up to about 20%, about or up to about 15%, about or up to about 10%, about or up to about 9%, about or up to about 8%, about or up to about 7%, about or up to about 6%, about or up to about 5%, about or up to about 4%, about or up to about 3%, about or up to about 2%, about or up to about 1 %, about or up to about 0.5%, about or up to about 0.2%, about or up to about 0.1%, about or up to about 0.01%, or about or up to about 0.001% of the bounded internal volume outside of the one or more core particles.

[0270] Embodiment 44. The method of any one of embodiments 24-43, wherein the outer shell comprises a dimension of about or at least 10 nm, about or at least 20 nm, about or at least about 30 nm, about or at least about 40 nm, about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm, about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or at least about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm, about or at least about 2 pm, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm, about or at least about 200 pm, about or at least about 300 pm, about or at least about 400 pm, about or at least about 500 pm, or about or at least about 1000 pm.

[0271] Embodiment 45. The method of any one of the preceding embodiments, wherein the one or more particles and / or the outer shell comprises one or more material of plastic, acrylic resin, styrene acrylic copolymer, vinyl acetate ethylene copolymer, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyurethane, epoxy resin, alkyd resin, cellulose acetate, silicone resin, a fluoropolymer resin, chlorinated rubber, a copolymer derived from maleic anhydride, ethylene vinyl acetate, polyethylene, polypropylene, polyamides (nylons), polyester resins, polybutadienes, thermally responsive polymers, latex, hydrocarbons, crude oil derivatives and / or petroleum derivatives, poloxamers, styrene-butadiene block copolymers, polymethylmethacrylate, polybutylmethacrylate, poly(tert-butyl acrylate)-poly(3-(triethoxysilyl)propyl methacrylate) (PtBA-PTPM), polystyrene latex polymer, carboxylated latex polymer, aminated latex polymer, colored polystyrene polymer (dye-infused and / or pigment-infused), colored polystyrene-based carboxylated latex polymer (dye-infused and / or pigment-infused), fluorescent polystyrene-based polymers, fluorescent polystyrene-based carboxylated latex polymers, fluorescent aminated polystyrene-based polymer, surfactant-free polystyrene, carboxylated surfactant-free polymer, polymethyl methacrylate (PMMA) latex polymer, and / or divinylbenzene-crosslinked polystyrene latex, plasticized polyvinyl chloride, plasticized nylon, plasticized polyethylene terephthalate, polyacrylonitrile, polychlorotrifluoroethylene, poly-4, 4'- isopropylidenediphenylene carbonate, polyethylene vinyl ester, polyvinyl chloride-diethyl fumarate, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers, acrylonitrile butadiene styrene, epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer, cyclic olefin polymer, poly dimethyl siloxane, poly ether ester ketone, polyetherimide, metal, metal oxide, metal nitride, inorganic material, silica, organic material, organic polymer, inorganic polymer, biological polymer, synthetic polymer, and combinations thereof.

[0272] Embodiment 46. The method of any one of the preceding embodiments, wherein the one or more particles and / or the outer shell comprises one or more material of a naturally occurring polymer and / or biological polymer comprising a nucleic acid (DNA, RNA), amino acid (peptide, protein), polysaccharide, or lipid.

[0273] Embodiment 47. The method of any one of the preceding embodiments, wherein at least the first optically active agent and / or at least the second optically active agent possesses an extinction in the electromagnetic spectrum between the x-ray / ultraviolet region (wavelengths >10 nm) and microwave / radio region (<10 cm).

[0274] Embodiment 48. The method of embodiment 23, wherein at least the first optically active agent and / or at least the second optically active agent exhibits a color in the visible electromagnetic spectrum and / or comprising an extinction, reflection, or scattering at a wavelength from about or at least about 300 nm to about or at least about 1200 nm.

[0275] Embodiment 49. The method of embodiment 47 or 48, wherein at least the first optically active agent and / or at least the second optically active agent comprises a color of one or more of white, black, red, orange, yellow, green, blue, indigo, violet, and variations of hue, shade, and intensity therebetween.

[0276] Embodiment 50. The method of any one of the preceding embodiments, wherein the one or more magnetically-responsive optically-variable particles comprises two optically active agents, three optically active agents, four optically active agents, or five or more optically active agents.

[0277] Embodiment 51 . The method of any one of the preceding embodiments, wherein at least the first optically active agent and / or at least the second optically active agent comprises a dye.

[0278] Embodiment 52. The method of embodiment 51 , wherein the dye comprises one or more of Rhodamine B, Congo Red, Crystal Violet, Methylene Blue, Acridine Orange, Nile Red, Malachite Green, Eosin Y, Cresol Red, Fluorescein, and Indigo.

[0279] Embodiment 53. The method of any one of the preceding embodiments, wherein at least the first optically active agent and / or at least the second optically active agent comprises a pigment.

[0280] Embodiment 54. The method of embodiment 53, wherein the pigment comprises a water-soluble pigment.

[0281] Embodiment 55. The method of embodiment 54, wherein the water-soluble pigment comprises one or more of anthocyanin, anthraquinone, carotenoid, violacein, melanin, pyocyanin, prodiginines, asperversin, benzoquinone, anthraquinone, and derivatives thereof.

[0282] Embodiment 56. The method of embodiment 53, wherein the pigment comprises one or more of Titanium White (PW6), Zinc White (PW4), Carbon Black (PBk7), Mars Black (PBk11), Iron Oxide Red (PR101), Cadmium Red (PR108), Alizarin Crimson (PR83), Cadmium Orange (PO20), Cadmium Yellow (PY35), Lemon Yellow (PY3), Chromium Green Oxide (PG17), Phthalo Green (PG7), Ultramarine Blue (PB29), Cobalt Blue (PB28), Cerulean Blue (PB35), Prussian Blue (PB27), Burnt Sienna (PBr7), Raw Umber (PBr7), Raw Sienna (PBr7), and Yellow Ochre (PY43).

[0283] Embodiment 57. The method of embodiment 53, wherein the pigment is an organic pigment.

[0284] Embodiment 58. The method of embodiment 53, wherein the pigment is an inorganic pigment.

[0285] Embodiment 59. The method of embodiment 57 or 58, wherein the organic pigment or inorganic pigment is a white pigment.

[0286] Embodiment 60. The method of embodiment 59, wherein the white pigment is one or more of lead white (2PbCO3-Pb(OH)2), kaolin, silica (SiC ), titanium dioxide (TiC / rutile and anatase), zinc oxide (ZnO), zinc sulfide (ZnS), and lithopone (ZnS + BaSCU).

[0287] Embodiment 61 . The method of embodiment 57 or 58, wherein the organic pigment or inorganic pigment is a black pigment.

[0288] Embodiment 62. The method of embodiment 61 , wherein the black pigment is one or more of coal (charcoal), groutite (o-MnOOH), manganite (y-MnOOH), hausmannite (MnsC ), carbon black, iron oxide black (FesC ), and spinel black (CuCtoCU)

[0289] Embodiment 63. The method of embodiment 57 or 58, wherein the organic pigment or inorganic pigment is a colored pigment.

[0290] Embodiment 64. The method of embodiment 63, wherein the colored pigment comprises a yellow pigment.

[0291] Embodiment 65. The method of embodiment 64, wherein the yellow pigment comprises one or more of yellow ochre (a-FeOOH), auric pigment (AS2S3), lead ochre (PbO), lead tin yellow (Pb2SnO4, PbSn2SiO?), Naples yellow (Pb(SbO3)2), zinc yellow (Zn2CrO4), Indian yellow (C19H16O10), iron oxide yellow (o-FeOOH), chromium titanium yellow ((Ti,Cr,Sb)O2), nickel titanium yellow ((Ti,Ni,Sb)C>2), lead yellow (PbCrO4), cadmium yellow (CdS), and bismuth yellow (BiVCM).

[0292] Embodiment 66. The method of embodiment 63, wherein the colored pigment comprises a red pigment.

[0293] Embodiment 67. The method of embodiment 66, wherein the red pigment comprises one or more of red ocher (a-Fe2O3), Terra di Siena (a-Fe2O3), vermilion (HgS), lead red (PbsCU), alizarin madder varnish, alizarin red (CuHsC ), iron oxide red (a-Fe2O3), molybdate red (Pb(Cr,S,Mo)O4), and cadmium red (Cd(S,Se)).

[0294] Embodiment 68. The method of embodiment 63, wherein the colored pigment comprises a green pigment.

[0295] Embodiment 69. The method of embodiment 68, wherein the green pigment comprises one or more of green earth (Fe silicates), Schweinfurt green (C4H6AS6CU4O16), chromium oxide green (CrcOs), chromium oxide hydrate green (CrOOH), and cobalt green (CtoTiC ).

[0296] Embodiment 70. The method of embodiment 63, wherein the colored pigment comprises a blue pigment.

[0297] Embodiment 71. The method of embodiment 70, wherein the blue pigment comprises one or more of lazurite (lapis lazuli), Egyptian blue (CaCuSi40io), azurite (2CuCO3'Cu(OH)2), malachite (CUCO3'CU(OH)2), cobalt blue (COAI2O4), Cobalt blue (COAI2O4), ultramarine blue: (Na6Al6SieO24(NaSn)), and iron blue (K[FelllFell(CN)6] xH2O).

[0298] Embodiment 72. The method of embodiment 63, wherein the colored pigment comprises a brown pigment.

[0299] Embodiment 73. The method of embodiment 72, wherein the brown pigment comprises one or more of burnt umber (Fe2O3 xMnC>2), brown ocher (o-Fe2O3 + Mn oxides), and limonite (mixture of different Fe oxides).

[0300] Embodiment 74. The method of embodiment 53, wherein the pigment is one or more of an oxide or oxide hydroxide pigment (TiO2, ZnO, o-Fe2O3, a-FeOOH, y-Fe2O3, FesC , Cr20s, CrOOH, PbO, PB3O4, MnsO4, -MnOOH, Sb2O3), a complex oxide pigment (COAI2O4, CuCr2O4, Co2TiO4, (Ti,Ni,Sb)O2, (Ti,Cr,Sb)O2), a carbonate hydroxide pigment (2PbCO3'Pb(OH)2, 2CuCO3'Cu(OH)2, CuCO3-Cu(OH)2), a sulfide / selenide pigment (ZnS, CdS, Cd(S,Se), CdSe, y-Ce2S3, HgS, AS2S3), a chromate / molybdate pigment (PbCrO4, Pb(Cr,S)O4, Pb(Cr,S,Mo)O4, ZnCrO4, BaCrO4, SrCrt U), a vanadate pigment (BiVO4, 4BiVO4-3Bi2MoOe), a stannate pigment (Pb2SnO4, PbSn2SiO?, Co2SnO4, CoSnOs), a phosphate pigment (Co3(PO4)2), an antimonate pigment (Pb(SbO3)2), an arsenate pigment (Cu(AsO3)2), an ultramarine pigment (Na6AleSi6O24(NaSn)), a hexacyanidoferrate / hexacyanoferrate pigment (K[FelllFell(CN)6] xH2O (x = 14-16)), an oxonitride pigment (CaTaO2N, LaTaON2), an elemental-based pigment (C, Al, Cu, Cu / Zn, Au), a spinelbased pigment, and a rutile-based metal pigment.

[0301] Embodiment 75. The method of embodiment 58, wherein the inorganic pigment is one or more of a transparent effect pigment, goniochromatic pigments, pearlescent pigment, metallic pigment, interference pigment, metallic effect pigment, fluorescent pigment, luminescent pigment, phosphorescent pigment, magnetic pigment, and anticorrosive pigment.

[0302] Embodiment 76. The method of embodiment 75, wherein the metallic pigment comprises one or more of aluminum, bronze, and copper metallic pigment.

[0303] Embodiment 77. The method of embodiment 75, wherein the pearlescent pigment comprises one or more of mica, titanium dioxide, and bismuth oxychloride.

[0304] Embodiment 78. The method of embodiment 75, wherein the fluorescent pigment comprises one or more fluorescent dye and pigment comprising a fluorescent mineral.

[0305] Embodiment 79. The method of embodiment 75, wherein the phosphorescent pigment comprises zinc sulfide and / or strontium aluminate.

[0306] Embodiment 80. The method of embodiment 75, wherein the interference pigment comprises titanium dioxide-coated mica and / or aluminum oxide-coated mica.

[0307] Embodiment 81 . The method of any one of the preceding embodiments, wherein at least the first optically active agent and / or at least the second optically active agent comprises an anisotropic particle.

[0308] Embodiment 82. The method of embodiment 81, wherein the anisotropic particle comprises a nanoparticle of the one or more metals, optionally comprising a nanorod of one or more of chromium (Cr), gold (Au), silver (Au), and aluminum (Al).

[0309] Embodiment 83. The method of any one of the preceding embodiments, wherein the at least two optically active agents comprise a plasmonic material.

[0310] Embodiment 84. The method of embodiment 83, wherein the plasmonic material comprises a pigment, particle, foil, and / or film.

[0311] Embodiment 85. The method of embodiment 84, wherein the plasmonic material comprises a polymer-film loaded with noble metal nanoparticles.

[0312] Embodiment 86. The method of embodiment 75, wherein the goniochromatic pigment comprises aluminum coated with magnesium fluoride embedded in chromium.

[0313] Embodiment 87. The method of any one of the preceding embodiments, further comprising coating the one or more magnetically-responsive optically-variable particles with one or more coating materials.

[0314] Embodiment 88. The method of embodiment 87, wherein the one or more coating materials comprises one or more organic substance, inorganic substance, biological substance, and combinations thereof.

[0315] Embodiment 89. The method of embodiment 87 or 88, wherein the one or more coating materials comprises one or more of a lubricant, surface treatment, and polishing agent.

[0316] Embodiment 90. The method of embodiment 89, wherein the one or more lubricant, surface treatment, and polishing agent comprises one or more of polytetrafluoroethylene (PTFE), hydroxylated selfassembled monolayers, vitreous enamel, ceria (cerium oxide), ceramics, anodized metals, and silica.

[0317] Embodiment 91. The method of any one of the preceding embodiments, further comprising formulating the one or more magnetically-responsive optically-variable particles.

[0318] Embodiment 92. The method of embodiment 91 , wherein formulating comprises suspending the magnetically-responsive optically-variable particles in a liquid.

[0319] Embodiment 93. The method of embodiment 92, wherein the liquid comprises one or more of an emulsifier, surfactant, solvent, viscosity modifier, salt, rheological agent, anti-microbial agent, pH adjuster, buffer, suspending agent, biological polymer, synthetic polymer, and organic molecule.

[0320] Embodiment 94. The method of embodiment 92 or 93, wherein the one or more magnetically- responsive optically-variable particles are present in a concentration of about or less than about 0.001% (w / v), about or less than about 0.1% (w / v), about or less than about 0.5% (w / v), about or less than about 1 % (w / v), about or less than about 2% (w / v), about or less than about 3% (w / v), about or less than about 4% (w / v), about or less than about 5% (w / v), about or less than about 6% (w / v), about or less than about 7% (w / v), about or less than about 8% (w / v), about or less than about 9% (w / v), about or less than about 10% (w / v), about or less than about 12% (w / v), about or less than about 14% (w / v), about or less than about 16% (w / v), about or less than about 18% (w / v), about or less than about 20% (w / v), about or less than about 25% (w / v), about or less than about 30% (w / v), about or less than about 35% (w / v), about or less than about 40% (w / v), about or less than about 50% (w / v), about or less than about 60% (w / v), or about or less than about 70% (w / v).

[0321] Embodiment 95. The method of embodiment 91, wherein formulating the one or more magnetically-responsive optically-variable particles comprises arranging into an array on a substrate.

[0322] Embodiment 96. The method of embodiment 95, wherein the substrate comprises a foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material.

[0323] Embodiment 97. The method of embodiment 95 or 96, wherein the one or more magnetically- responsive optically-variable particles cover a surface area of about or less than about 1 %, about or less than about 5%, about or less than about 10%, about or less than about 15%, about or less than about 20%, about or less than about 25%, about or less than about 30%, about or less than about 35%, about or less than about 40%, about or less than about 45%, about or less than about 50%, about or less than about 55%, about or less than about 60%, about or less than about 65%, about or less than about 70%, about or less than about 75%, about or less than about 80%, about or less than about 85%, about or less than about 90%, about or less than about 95%, or about or less than about 99%.

[0324] Embodiment 98. The method of any one of embodiments 95-97, wherein at least a portion of the substrate is transparent to at least a portion of the visible electromagnetic (EM) spectrum and / or opaque.

[0325] Embodiment 99. The method of any one of embodiments 95-98, wherein the substrate comprises a material of one or more of glass, sapphire, diamond, silicon, organic polymers, organic materials, biological polymers, metal oxides, quartz, plastic, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers (TPE), acrylonitrile butadiene styrene (ABS), epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer (COC) cyclic olefin polymer (COP), poly dimethyl siloxane (PDMS), poly ether ester ketone (PEEK), polyetherimide (ULTEM) and nylon.

[0326] Embodiment 100. The method of embodiment 91, wherein formulating the one or more magnetically-responsive optically-variable particles comprises assembling the one or more magnetically- responsive optically-variable particles into a fiber, thread, yarn, twine, and / or material thereof.

[0327] Embodiment 101. A method of manufacturing one or more magnetically-responsive optically- variable particles, the method comprising generating one or more Janus particles in a microfluidic channel, wherein the Janus particle is composed of at least one magnetic material, applying a magnetic field to the microfluidic channel to induce anisotropy in the one or more Janus particles, and curing the one or more Janus particles in the magnetic field using a thermal treatment to generate one or more magnetically- responsive particles optically-variable particles.

[0328] Embodiment 102. The method of embodiment 101 , wherein the Janus particles are generated using two or more materials, optionally wherein the materials are thermally responsive polymers, and further optionally wherein the two or more materials have distinct optical properties.

[0329] Embodiment 103. The method of embodiment 101 or 102, wherein the microfluidic channel comprises an elongated portion of the channel which alters the shape of the Janus particles that are generated.

[0330] Embodiment 104. The method of any one of embodiments 101-103, wherein the induced anisotropy comprises orienting the magnetic material to one portion of the one or more Janus particles to generate a magnetic dipole.

[0331] Embodiment 105. The method of any one of embodiments 101-104, wherein the thermal treatment comprises one or more of microwave treatment, ultraviolet (UV) polymerization, and induction.

[0332] Embodiment 106. The method of any one of embodiments 101-105, further comprising disposing the one or more magnetically-responsive optically-variable particles onto a surface to generate a 2- dimensional monolayer or array of the one or more magnetically-responsive optically-variable particles.

[0333] Embodiment 107. The method of embodiment 106, further comprising applying a second magnetic field to the one or more magnetically-responsive particles to orient the one or more magnetically- responsive particles on the surface such that an equivalent portion of the surface area of each of the one or more magnetically-responsive particles is exposed relative to one another within the 2-dimensional monolayer or array.

[0334] Embodiment 108. The method of embodiment 106 or 107, further comprising coating at least a portion of the exposed surface area of the one or more magnetically-responsive optically-variable particles with at least one optically active agent.

[0335] Embodiment 109. The method of any one of embodiments 101-108, further comprising encapsulating the one or more magnetically-responsive optically-variable particles in a shell.

[0336] Embodiment 110. A composition comprising one or more magnetically-responsive optically- variable particles made by the method of any one of embodiments 1 -109.

[0337] Embodiment 111. A kit comprising one or more magnetically-responsive particles and one or more optically active agent.

[0338] Embodiment 112. The kit of embodiment 111 , further comprising a means for applying a magnetic field and / or a substrate to dispose the one or more magnetically-responsive particles upon.

[0339] Embodiment 113. A kit comprising magnetic material, one or more particles, a means for applying a magnetic field, a substrate to dispose the one or more magnetically-responsive particles upon, at least one optically active agent.EQUIVALENTS

[0340] While the disclosure has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains and as may be applied to the essential features hereinbefore set forth and as follows in the scope of the appended claims.

[0341] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific embodiments described specifically herein. Such equivalents are intended to be encompassed in the scope of the following claims.INCORPORATION BY REFERENCE

[0342] All patents and publications referenced herein are hereby incorporated by reference in their entireties.

[0343] The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure.

[0344] As used herein, all headings are simply for organization and are not intended to limit the disclosure in any manner. The content of any individual section may be equally applicable to all sections.

Claims

CLAIMSWhat is claimed is:

1. A method of manufacturing one or more magnetically-responsive optically-variable particles, the method comprising:(i) attaching a magnetic material to one or more particles to generate one or more magnetically- responsive particles;(ii) applying a magnetic field to the one or more magnetically-responsive particles such that each of the one or more magnetically-responsive particles are equivalently oriented relative to the direction of the magnetic field; and(iii) coating at least a portion of the exposed surface area of the one or more magnetically-responsive particles with at least a first optically active agent, wherein each of the one or more magnetically-responsive optically-variable particles are coated on an equivalent portion of the exposed surface area relative to the direction of the magnetic field, to generate one or more magnetically-responsive optically-variable particles.

2. The method of claim 1 , further comprising applying a magnetic field, after the attaching step, to separate the one or more magnetically-responsive particles from the one or more particles that did not attach magnetic material.

3. The method of any one of claims 1 or 2, wherein applying the magnetic field in step (ii) further comprises disposing the one or more magnetically-responsive particles onto a surface to generate a 2-dimensional array of the one or more magnetically-responsive particles such that an equivalent portion of the surface area of each of the one or more magnetically-responsive particles is exposed within the 2-dimensional array relative to the direction of the magnetic field.

4. The method of claim 3, wherein disposing the one or more magnetically-responsive particles onto the surface comprises spraying, evaporating, or blotting onto the surface.

5. The method of claim 1 , further comprising generating the one or more particles.

6. The method of claim 5, wherein generating the particles comprises performing one or more of evaporation, chemical or physical self-assembly, droplet-based microfluidics, polymerization (ultraviolet polymerization), adsorption, coacervation, mixing, and extrusion.

7. The method of claim 6, wherein generating the particles comprises droplet-based microfluidics.

8. The method of any one of claims 5-7, wherein generating the particles comprising forming Janus particles.

9. The method of any one of the preceding claims, wherein the attaching further comprises microfluidics to adhere the magnetic material to the one or more particles; and / or wherein adhering the magnetic material to the one or more particles comprises exposure to microwave radiation, thermal treatment, or UV-crosslinking.

10. The method of any one of the preceding claims, wherein the one or more particles and / or one or more magnetically-responsive particles and / or one or more magnetically-responsive optically- variable particles comprises a dimension of about 50 nm to about 100 pm, or about or at least about 50 nm, about or at least about 60 nm, about or at least about 70 nm, about or at least about 80 nm, about or at least about 90 nm, about or at least about 100 nm, about or at least about 150 nm, about or at least about 200 nm, about or at least about 250 nm, about or at least about 300 nm, about or at least about 350 nm, about or at least about 400 nm, about or at least about 450 nm, about or at least about 500 nm, about or at least about 550 nm, about or at least about 600 nm, about or at least about 650 nm, about or at least about 700 nm, about or at least about 750 nm, about or at least about 800 nm, about or at least about 850 nm, about or at least about 900 nm, about or at least about 950 nm, about or at least about 1000 nm, about or at least about 2 pm, about or at least about 3 pm, about or at least about 4 pm, about or at least about 5 pm, about or at least about 6 pm, about or at least about 7 pm, about or at least about 8 pm, about or at least about 9 pm, about or at least about 10 pm, about or at least about 20 pm, about or at least about 50 pm, about or at least about 100 pm.

11. The method of any one of the preceding claims, wherein the magnetic material is or comprises one or more of magnetic beads and magnetic particles.

12. The method of any one of the preceding claims, wherein the magnetic material is ferromagnetic, ferrimagnetic, antiferromagnetic, diamagnetic, paramagnetic, superparamagnetic, and / or antiferromagnetic.

13. The method of any one of the preceding claims, wherein the magnetic material is or comprises one or more of an inorganic, organic, or carbon-based material.

14. The method of any one of the preceding claims, wherein the magnetic material is or comprises one or more of iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), manganese (Mn), chromium (Cr), samarium (Sm), alloys or oxides thereof; alloys, intermetallic, and / or oxides of Fe, Co, Ni, Zn, Mn, Sm; oxides are of iron, Fe2Os, FeO, and / or Fe3O4; ferrite material and / or doped materials of Co, Ni, Zn, and / or Mn:FexOy, and / or magnetitetetracyanoethylene (TCNE) salts, [Fe(C5Me5)2]+[TCNE]‘-, Li[TCNE], [MnllTPP][TCNE]« (TPP = tetraphenylporphyrin), [Fell(TCNE)(NCMe)2][FelllCl4], Mnll(TCNE)l(OH2), Mnll(TCNE)[C4(CN)8]i / 2, Fe(TCNE)[C4(CN)8]i / 2, Mnll(TCNE)3 / 2(l3)i / 2, VI l[TCNE]x(x « 2), C7H5CIN3Se4, magnetic organic polymers, and polymer-bonded magnets.

15. The method of any one of the preceding claims, wherein coating further comprises spraying, sputtering, painting, glow discharging, or otherwise applying the at least one optically active agent onto at least a portion of the external surface area of the one or more magnetically-responsive particles.

16. The method of any one of the preceding claims, further comprising encapsulating the magnetically- responsive optically-variable particles in an outer shell.

17. The method of claim 16, wherein encapsulating the magnetically-responsive particles in an outer shell comprises performing one or more of interfacial polymerization, in situ polymerization, coacervation, layer-by-layer growth, swelling, adsorption, sol-gel encapsulation, suspension crosslinking, lyophilization, spay drying, co-extrusion, fluidized bed spray coating, and phase inversion precipitation.

18. The method of claim 16 or 17, wherein the outer shell is optically transparent to at least a portion of electromagnetic radiation between frequencies of about 10 nm to about 10 cm.

19. The method of any one of claims 16-18, wherein encapsulating the magnetically-responsive particles in an outer shell further comprises removing a sacrificial layer of material resulting in a bounded internal volume filled with one or more of gas, liquid, polymer, semisolid, and solid material.

20. The method of any one of the preceding claims, wherein the one or more particles and / or the outer shell comprises one or more material of plastic, acrylic resin, styrene acrylic copolymer, vinyl acetate ethylene copolymer, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyurethane, epoxy resin, alkyd resin, cellulose acetate, silicone resin, a fluoropolymer resin, chlorinated rubber, a copolymer derived from maleic anhydride, ethylene vinyl acetate, polyethylene, polypropylene,polyamides (nylons), polyester resins, polybutadienes, thermally responsive polymers, latex, hydrocarbons, crude oil derivatives and / or petroleum derivatives, poloxamers, styrene-butadiene block copolymers, polymethylmethacrylate, polybutylmethacrylate, poly(tert-butyl acrylate)-poly(3- (triethoxysilyl)propyl methacrylate) (PtBA-PTPM), polystyrene latex polymer, carboxylated latex polymer, aminated latex polymer, colored polystyrene polymer (dye-infused and / or pigment- infused), colored polystyrene-based carboxylated latex polymer (dye-infused and / or pigment- infused), fluorescent polystyrene-based polymers, fluorescent polystyrene-based carboxylated latex polymers, fluorescent aminated polystyrene-based polymer, surfactant-free polystyrene, carboxylated surfactant-free polymer, polymethyl methacrylate (PMMA) latex polymer, and / or divinylbenzene-crosslinked polystyrene latex, plasticized polyvinyl chloride, plasticized nylon, plasticized polyethylene terephthalate, polyacrylonitrile, polychlorotrifluoroethylene, poly-4, 4'- isopropylidenediphenylene carbonate, polyethylene vinyl ester, polyvinyl chloride-diethyl fumarate, polyethylene terephthalate, polycarbonate, polymethyl methacrylate (acrylic), polyethylene, polyurethane, polypropylene, thermoplastic elastomers, acrylonitrile butadiene styrene, epoxies and epoxy-based photoresists, hydrogels, cyclic olefin copolymer, cyclic olefin polymer, poly dimethyl siloxane, poly ether ester ketone, polyetherimide, metal, metal oxide, metal nitride, inorganic material, silica, organic material, organic polymer, inorganic polymer, biological polymer, synthetic polymer, and combinations thereof.

21. The method of any one of the preceding claims, wherein at least the first optically active agent and / or at least the second optically active agent possesses an extinction in the electromagnetic spectrum between the x-ray / ultraviolet region (wavelengths >10 nm) and microwave / radio region (<10 cm).

22. The method of claim 21, wherein at least the first optically active agent and / or at least the second optically active agent exhibits a color in the visible electromagnetic spectrum and / or comprising an extinction, reflection, or scattering at a wavelength from about or at least about 375 nm to about or at least about 875 nm (visible spectrum).

23. The method of claim 21 or 22, wherein at least the first optically active agent and / or at least the second optically active agent comprises a color of one or more of white, black, red, orange, yellow, green, blue, indigo, violet, and variations of hue, shade, and intensity therebetween.

24. The method of any one of the preceding claims, further comprising coating the one or more magnetically-responsive optically-variable particles with one or more coating materials.

25. The method particle of claim 24, wherein the one or more coating materials comprises one or more organic substance, inorganic substance, biological substance, and combinations thereof.

26. The method of claim 24 or 25, wherein the one or more coating materials comprises one or more of a lubricant, surface treatment, and polishing agent.

27. The method of claim 26, wherein the one or more lubricant, surface treatment, and polishing agent comprises one or more of polytetrafluoroethylene (PTFE), hydroxylated self-assembled monolayers, vitreous enamel, ceria (cerium oxide), ceramics, anodized metals, and silica.

28. The method of any one of the preceding claims, further comprising formulating the one or more magnetically-responsive optically-variable particles into a liquid or suspension.

29. The method of claim 28, further comprising applying the liquid or suspension to a foil, film, thin film, plastic, thin plastic, tape, and / or paper substrate and / or material.

30. The method of claim 28, wherein formulating the one or more magnetically-responsive optically- variable particles comprises assembling the one or more magnetically-responsive optically-variable particles into a fiber, thread, yarn, twine, and / or material thereof.

31. A method of manufacturing one or more magnetically-responsive optically-variable particles, the method comprising:(i) generating one or more Janus particles in a microfluidic channel, wherein the one or more Janus particles are composed of at least one magnetic material;(ii) applying a magnetic field to the microfluidic channel to induce anisotropy in the one or moreJanus particles; and(iii) curing the one or more Janus particles in the magnetic field using a curing treatment to generate one or more magnetically-responsive particles optically-variable particles.

32. The method of claim 31 , wherein the Janus particles are generated using two or more materials, optionally wherein the materials are thermally responsive polymers, and further optionally wherein the two or more materials have distinct optical properties.

33. The method of claim 31 or 32, wherein the microfluidic channel comprises an elongated portion of the channel which alters the shape of the Janus particles that are generated.

34. The method of any one of claims 31-33, wherein the induced anisotropy comprises orienting the magnetic material to one portion of the one or more Janus particles to generate a magnetic dipole.

35. The method of any one of claims 31-34, wherein the curing treatment comprises one or more of microwave treatment, thermal treatment, ultraviolet (UV) polymerization, and induction.

36. The method of any one of claims 31 -35, further comprising disposing the one or more mag netically- responsive particles optically-variable particles onto a surface to generate a 2-dimensional monolayer or array.

37. The method of claim 36, further comprising applying a second magnetic field to the one or more magnetically-responsive particles optically-variable particles to orient the magnetically-responsive particles optically-variable particles on the surface such that an equivalent portion of the surface area of each of the one or more magnetically-responsive particles optically-variable particles is exposed relative to one another within the 2-dimensional monolayer or array relative to the direction of the magnetic field.

38. The method of claim 37, further comprising coating at least a portion of the exposed surface area of the one or more magnetically-responsive particles optically-variable particles with at least a first optically active agent.

39. The method of any one of claims 31-38, further comprising encapsulating the one or more magnetically-responsive optically-variable particles in a shell.

40. A composition comprising one or more magnetically-responsive optically-variable particles made by the method of any one of claims 1 -39.

41. A kit comprising one or more components for performing the method of any one of claims 1-39.

Images