3D microprinting with molecular swimming body precursors

Abstract

Compositions and methods for three-dimensional (3D) printing of a variety of products are described. The composition comprises (i) a photoredox component comprising an electron donor and a redox shuttle, and (ii) one or more photoinert materials. The disclosed compositions and methods related to 3D nanoprinting techniques mainly utilize physical processes of phase separation induced by molecular aggregation from light energy input. The driving force of molecular aggregation comes from a photoredox active component in the vicinity of one or more photoinert materials (e.g., molecules to undergo molecular aggregation). Preferably, the collision between the photoredox active component and one or more photoinert materials provides a general phase separation process. The photoredox active component acts as an active bath, allowing any submerged inert reagent to inherit the active properties of the photosensitizer.

Description

TECHNICAL FIELD

[0001] The present invention generally belongs to the field of additive manufacturing, such as three-dimensional (3D) printing, and in particular relates to compositions and methods for three-dimensional printing involving molecular aggregation and phase separation of materials for the fabrication of desired products. BACKGROUND

[0002] In principle, the ability to control interactions at the molecular scale would enable the manipulation of the assembled structure and macroscopic properties of materials. Typically, since these interactions stem from chemical bonds or van der Waals forces, it is necessary to adjust the system composition, molecular configuration, or surrounding environment to tune these interactions and control the properties and phases of materials. However, a set of pseudo-interactions 6 One prominent example of such non-equilibrium interactions is the light-induced phase transition in solid-state materials, where intense laser pulses can strongly interact with the crystal 7 , electronic structure 8 or spin state 9 of the constituent atoms, ultimately leading to the recent discovery of metastable phases with extraordinary properties, including superconductivity 10 , insulator-to-metal transition 8 , geometric phase 11 , ferromagnetism 12 and ferroelectricity 13 . However, this strategy of strong interaction manipulation of atoms or molecules cannot be directed to apply in solution due to their high laser energy. As found in biological systems 1-3 , the breaking of interaction symmetries provided by thermodynamic constraints offers a new way to induce dissipative phases that cannot be achieved at equilibrium 4,5 . Recently, it has been found that chemical reactions on active colloids can generate apparent interactions between particles, leading to aggregation and phase separation 14-16 . However, there is still a need to develop compositions that can be used to fabricate products without the above-mentioned bottlenecks.

[0003] It is therefore an object of the present invention to provide improved compositions and methods for additive manufacturing.

[0004] It is also an object of the present invention to provide improved compositions and methods for three-dimensional printing involving molecular aggregation and phase separation, but without extensive covalent crosslinking between the aggregated components. SUMMARY

[0005] Compositions and methods are described that can be used to fabricate a variety of products by 3D printing. The compositions contain: (i) a photo-redox component containing an electron donor and a redox shuttle, and (ii) one or more photo-inert materials. The compositions can be in the form of a solution, suspension, colloid, gel, emulsion, etc. The compositions can be in the form of a solution, suspension, gel, emulsion, etc. The compositions can be in the form of a solution. In some forms, the compositions are not in the form of a colloid. In some forms, the compositions are not in the form of a colloid containing titanium (IV) oxide. In some forms, the compositions are substantially free of titanium (IV) oxide, i.e., contain less than 50%, 40%, 30%, 20%, 10%, 5% by weight of titanium (IV) oxide. Typically, the electron donor contains a photosensitizer, and the one or more photo-inert materials are materials used to fabricate the desired product.

[0006] The disclosed compositions and methods involving 3D nanofabrication techniques primarily utilize physical processes of phase separation induced by molecular aggregation from light energy input. These physical processes avoid the need for covalent bond cleavage and formation between atoms and molecules used in traditional laser direct writing techniques. The driving force for molecular aggregation comes from the photo-redox active component in the vicinity of the one or more photo-inert materials (e.g., molecules that are to undergo molecular aggregation). Preferably, collisions between the photo-redox active component and the one or more photo-inert materials provide a conventional phase separation process. Molecular aggregation with different photo-inert materials (such as those containing inert tracer particle systems, etc.) is shown in the examples, showing direct laser printing of a variety of desired materials. Here, it is shown that proteins, DNA nanostructures, and functional nanoscale organic electronic elements (including conductive nanowires and field effect transistors) can be directly fabricated from photo-redox inks.

[0007] Without wishing to be bound by theory, it is believed that the photo-redox reaction results in an apparent attractive potential between excited molecules, inducing Avrami-like phase transitions of photo-reactive molecules (e.g., dye molecules). More importantly, the photo-redox active solution acts as an active bath, allowing any immersed inert reagents to inherit the active properties of the photo-redox dye. As a result, universal light-induced aggregation and phase transitions can be observed for cargo molecules and colloids. This light-induced phase transition as a novel 3D printing technique enables laser direct writing to print general-purpose materials, including biological molecules and electronic polymers. This new discovery reveals a new field of photo-redox reactions where molecular-scale mechanical effects can be used as a new tool for nanofabrication and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figures 1A-1H. Photo-redox induced aggregation. a, Stepwise electron transfer process (red arrows) in a classical DSSC, while charge recombination (blue arrows) can complete the electron cycle (blue rectangle) without electrodes and induce intermolecular interactions. b, Schematic representation of photo-redox interactions leading to molecular aggregation. c, Successive fluorescence images showing D5 aggregates within the illuminated area (red circle). d, Patterning of the university initials in a solution under structured illumination. e, Fluorescence intensity evolution fitted with the KJMA model at different illumination powers from 0 to 69 kW / cm 2 . Inset: Exponential decrease of the energy barrier with the light intensity (I). f, Fluorescence lifetime showing a dynamic quenching process of the redox / shuttling as the lifetime decreases proportionally to the fluorescence intensity as shown in the inset Stern-Volmer plot. g, Evolution of the dye / shuttling agent concentration under continuous illumination as extracted from TCSPC experiments. h, Fluorescence intensity evolution of the redox-shuttling agent at different concentrations (from 9.5 to 30 mM) fitted with the KJMA model, inset showing the power law dependence of the conversion rate constant K with the redox-shuttling agent concentration, Avrami factor n = 4.

[0009] Figures 2A-2E . Attractive forces of microbeads in a photo-redox bath. a, Successive images showing the aggregation process of silica microbeads in a photo-redox bath under uniform global illumination. b, Force spectrum of 2 μm silica beads immersed in a photo-redox bath measured by optical tweezers under uniform 465 nm light illumination with intensity varying from 0 to 6.0 W / cm 2 . Inset shows the dissipation rate (J) of the beads increasing with the light intensity (I). c, Effective temperature T eff of immersed silica beads with diameters from 0.5 to 5 μm under different illumination intensities (I). Inset: Effective temperature T eff is inversely related to the bead diameter (D) and scales as T eff ~ D -2 .d, Schematic representation of the attractive potential induced between immersed microbeads in a photo-redox environment. e, Force F a between two silica beads in a photo-redox bath showing an attractive force increasing with the illumination intensity (I). Inset: Attractive potential E_attr is linearly related to the illumination intensity (I).

[0010] Figures 3A-3D . Photo-redox induced phase transition of inert cargo. a, Time-lapse images of photo-redox induced aggregation of cargo from nanoscale to molecular scale. b, Relative fluorescence intensity (I t / I0) represents the aggregation-nucleation-growth stage under irradiation. Red and blue dots represent the fluorescence intensity evolution of FTIC molecules and CdTe quantum dots in the photoredox bath. Dashed lines are drawn to guide the eye. c, Timed transmission image of the FITC solution under focused irradiation in Figure 3b. d, Timed transmission image of photoredox-induced BSA precipitation. The right image shows the SEM image of the solid BSA precipitate.

[0011] Figures 4A-4I 3D laser-written microstructures of biomolecules. a, Illustration of the laser-written process for micro-line arrays. b, SEM image of a BSA micro-line array and detailed structure of a single line. c, Raman mapping image of the BSA micro-line array in b. df, SEM images of microscale antennas, pyramids, and line arrays printed with BSA using a two-photon 3D laser printer. gi, SEM images of micron-scale DNA structures of double-helix arrays, helices, and nanowires printed using a two-photon 3D laser printer.

[0012] Figures 5A-5D Laser direct writing using electronic polymers. a, SEM image of the printed PEDOT:PSS nanowire (green) between two Au electrodes (yellow). Inset: AFM image of the nanowire showing its thickness. b, Nanowire thickness and conductivity ( The conductivity is proportional to the exposure time (t) while maintaining good conductivity. Illustration: The IV curves of the nanowires show metallic properties. c, P3HT nanowires behave like typical p-type FETs because their source-drain current (Id) is proportional to the exposure time (t). ds With gate voltage (V) gs Modulation was performed from 0 to -50 V. d, Transport curve of the P3HT nanowire FET. Inset: SEM image of the P3HT nanowire (yellow). Detailed Implementation

[0013] I. Definition

[0014] "Photoinert materials" are materials that, when exposed to light in the absence of photoredox active components, exhibit substantially no photoinduced physical aggregation in a medium (e.g., a solution, colloid, suspension, or other medium in which the material can diffuse).

[0015] A "photoredox active component" refers to a system containing an electron donor and an electron acceptor, wherein the electron donor is able to transfer an electron to the electron acceptor upon excitation (e.g., by photon absorption), initiating a redox reaction. The electron donor can be referred to as a photosensitizer. An example of an electron acceptor is a redox shuttle. Therefore, a photoredox active component can comprise a combination of a photosensitizer and a redox shuttle.

[0016] "Photosensitizer" refers to a compound that absorbs light of a specific wavelength and converts it into useful energy.

[0017] A "redox shuttle" is a molecule that possesses sufficient electrochemical stability, diffusivity, and a suitable redox potential to reversibly undergo an electron transfer reaction. A reversible shuttle can gain electrons through reduction (e.g., from an excited molecule) and lose electrons through oxidation, repeating this process multiple times. Examples include dimethyl terephthalate, quinones (e.g., benzoquinone and dihydroxyanthraquinone), naphthalene, ferrocene, and (2,2,6,6-tetramethylpiperidin-1-yl)oxy radical (TEMPO).

[0018] "High electron recombination rate" refers to a rate between approximately ~1 x 10⁻⁶. -10 s -1 and ~1 x 10 -8 s -1 The quenching rate constant (k) between q ), such as ~1.75 x 10 -9 s -1 wait.

[0019] II. Composition

[0020] Compositions and methods for manufacturing a variety of products via 3D printing are described. Preferably, the composition comprises: (i) a photoredox component comprising an electron donor and a redox shuttle, and optionally (ii) one or more photoinert materials. The composition may be in the form of a solution, suspension, colloid, gel, emulsion, etc. The composition may be in the form of a solution, suspension, gel, emulsion, etc. The composition may be in solution form. In some forms, the composition is not in colloidal form. In some forms, the composition is not in colloidal form containing titanium dioxide (IV). In some forms, the composition is substantially free of titanium dioxide (IV), i.e., contains less than 50%, 40%, 30%, 20%, 10%, or 5% titanium dioxide (IV) by weight. Some materials that may be included in the composition include epoxy-based photoresists, proteins, enzymes, nucleic acids (e.g., synthetic and natural), and electron polymers (such as P3HT, NDI2OD-T2, PEDOT:PSS, inorganic quantum dots, etc.). Typically, the electron donor contains a photosensitizer, while one or more photoinert materials are materials used to manufacture the desired product.

[0021] Currently, 3D printing technologies, such as nanoscale and / or microscale 3D printing, rely on the polymerization of resins in which a focused laser beam is used to initiate cross-linking and curing of the resin. The advantage of this technology is its high resolution, in which sub-200 nm resolution has been demonstrated. However, one bottleneck is the limited selection of materials for cross-linking and curing. The compositions and methods described herein relate to a new molecular swimmer composition that, by mixing with any material, transforms the composition into a precursor that can be used for 3D printing via laser direct writing.

[0022] Embodiments demonstrate that in a composition containing a photo-redox active component, such as a composition containing a dye-redox shuttle solution, although no net chemical reaction occurs upon photoexcitation, the reversible photo-redox reaction induces a substantial effective attractive potential between the molecules, leading to molecular aggregation upon irradiation. In some cases, there is an incubation period between the irradiation time (photoexcitation) and the molecular aggregation. Importantly, the components of the composition (e.g., a dissipative preparation containing a photo-redox active component) act as a non-equilibrium active bath, transferring momentum from the active molecules (e.g., molecules of the photo-redox active component) to one or more photo-inert materials (e.g., suspended inert colloids and passive solute molecules), thereby inducing an effective attractive potential between the one or more photo-inert materials.

[0023] As a result, the photo-redox active component (e.g., a component containing a dye-redox shuttle system) can be used as a light-driven molecular engine to induce aggregation and phase separation of any embedded photo-inert material. A 3D nanofabrication technology has been developed that allows direct fabrication of nanostructures and / or microstructures using arbitrary materials, including biological molecules and electronic materials. Thus, the disclosed methods facilitate direct printing of operational nanoscale / microscale electronic components, including conductive nanowires and field effect transistors.

[0024] The disclosed compositions and methods relating to 3D nanofabrication technology primarily utilize the physical process of phase separation, which is induced by molecular aggregation from light energy input. These physical processes avoid the need for covalent bond cleavage and formation between atoms and molecules used in traditional laser direct writing technologies. The driving force for molecular aggregation comes from the photo-redox active component in the vicinity of the one or more photo-inert materials (e.g., molecules to undergo molecular aggregation). Preferably, collisions between the photo-redox active component and the one or more photo-inert materials provide the conventional phase separation process. Embodiments show molecular aggregation with different photo-inert materials, such as those containing inert tracer particle systems, showing direct laser printing of a wide range of desired materials.

[0025] In certain instances, the photo-redox active component containing a dye-redox shuttle system can be used to construct a light-driven molecular engine to induce the aggregation and phase separation of any embedded passive cargo, which is, to the best of the inventors' knowledge, the first validation of a simple light-controlled molecular engine. Furthermore, to the best of the inventors' knowledge, this is the first validation of photo-redox active components (e.g., photo-redox active components containing photo-redox molecular systems) to induce tracer particle phase separation on a molecular to micrometer scale. Finally, printed nanoscale / micrometer scale structures composed of biomolecules and / or electronic polymers printed by the disclosed phase separation method in a commercial laser direct write machine provides a new method of printed nanotechnology to achieve smaller feature sizes and provides the ability to print general purpose materials.

[0026] A. Photo-redox active component

[0027] Preferably, the photo-redox active component contains an electron donor and a redox shuttle.

[0028] i. Electron donor component

[0029] Preferably, the electron donor component contains a photosensitizer. In some forms, the electron donor contains a photo-oxidation-reduction active dye, which comprises an organic dye such as a photoactivatable fluorophore, for example a fluorescent dye. Photoactivatable fluorophores are described in Li and Zheng, Phtochem. Photobiol. Sci. 2012, 11(3), 460-471, the contents of which description of photoactivatable fluorophores are incorporated herein by reference. Specific non-limiting examples of photosensitizers include, but are not limited to, 3-(5-(4-(diphenylamino)styryl)thiophene-2-yl)-2-cyanoacrylic acid, chlorothiazide, curcumin, porphyrin, phenothiazine, sulfonamide, monogalacturonide A, anthraquinone, hypericin, tolporphyrin, chlorophyllin, and tetracycline. A variety of organic dyes used in dye-sensitized solar cells can be used as photosensitizers. These materials include a variety of organic dyes used in dye-sensitized solar cells that can be used in photo-oxidation-reduction active dyes, such as: (E)-3-(6-(4-(bis(2',4'-dimethoxy-[1,1'-biphenyl]-4-yl)amino)phenyl)-4,4-dihexyl-4H- cyclopenta[2,1-b:3,4-b']dithiophen-2-yl)-2-cyanoacrylic acid (D51), 5-carboxy-2-[[3-[(2,3- dihydro-1,1-dimethyl-3-ethyl-1H-benzo[e]indolium-2-yl)methyl]-2-hydroxy-4-oxo-2- cyclobuten-1-yl]methyl]-3,3-dimethyl-1-octyl-3H-indolium (SQ2), 1-butyl-N,N,N-butyl-[(2,2':6',2''- terpyridinato)-4,4',4''-tricarboxylato(3-)-κN1,κN1',κN1'']tris(thiocyanato-κN)ruthenium acid (4- )ammonium hydride (2:2:1) (N749), and 3-(2-((E)-2-((E)-3-((Z)-2-(3-(2-carboxyethyl)-1,1-dimethyl-1,3- dihydro-2H-benzo[e]indol-2-yl)ethylidene)-2-chlorocyclohex-1-en-1-yl)vinyl)-1,1-dimethyl-1H- benzo[e]indol-3-ium-3-yl)propanoate (MK245).

[0030] ii. Redox shuttle

[0031] Preferred redox shuttles are those that have high electron complexation rates. Examples of redox shuttles include, but are not limited to, halide redox shuttles, organic redox shuttles, transition metal complex redox shuttles, tandem redox shuttles, or combinations thereof. Masud and Kim, ACS Omega 2023, 8(7), 6139-6163; and U.S. Patent 7851092 describe redox shuttles, the contents of which describing redox shuttles are incorporated herein by reference. Specific non-limiting examples of redox shuttles include quinones (e.g., benzoquinone and dihydroxyanthraquinone), dimethyl terephthalate, naphthazarine, ferrocene, and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO), or combinations thereof.

[0032] B. Photo-inert materials

[0033] Preferably, the composition contains one or more photo-inert materials. Typically, these are materials used to make a desired product, such as during 3D printing. Preferably, the one or more photo-inert materials undergo molecular aggregation and phase separation upon exposure to / upon exposure to a light source. Preferably, for these photo-inert materials, substantially no photo-induced physical aggregation occurs in a medium (e.g., a solution, a colloid, a suspension, or other medium in which the material can diffuse) when the composition is exposed to light in the absence of a photo-oxidation-reduction active component.

[0034] Examples of optically inert materials include, but are not limited to, synthetic polymers (e.g., organic electronic polymers, particularly solution-processable electronic polymers), natural polymers, thermoplastic polymers, nanoparticles, quantum dots, microparticles, biomolecules (proteins, DNA, etc.), dyes (e.g., fluorescein). Preferably, in these cases, the dye is not reactive with the redox shuttle under irradiation. Nanoparticles and microparticles can be polymeric, non-polymeric, liposomes, combinations thereof, or mixtures thereof. Preferred examples of organic electronic polymers are those containing a π-conjugated system, such as poly(3,4-ethylenedioxythiophene), poly(3-hexyl-thiophene), indacenodithiophene-cobenzothiadiazole (IDTBT) polymers, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, benzodifuran dione-based oligo(p-phenylenevinylene), diketopyrrolopyrrole (DPP)-based semiconducting polymers, diketopyrrolopyrrole-based PDPPT3 polymers, copolymers thereof, blends thereof, and the like. Organic electronic polymers are described in Kukhta and Luscombe, Chem. Commun. 2022, 58, 6982-6997, the contents of which describing organic electronic polymers are incorporated herein by reference. Other examples of polymers include polyamideimide, polyether sulfone, polyetherimide, polyarylate, polysulfone, polyamide, polymethyl methacrylate, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polystyrene, polyether ether ketone, polytetrafluoroethylene, polyamide 6,6, polyamide 11, polyphenylene sulfide, polyethylene terephthalate, polyformaldehyde, polypropylene, high-density polyethylene, low-density polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, natural rubber, polydimethylsiloxane, polyformaldehyde, polycarbonate, polyethylene terephthalate, polyether ether ketone, nylon 6, polyamideimide, polysulfone, polyphenylene sulfide, polyether sulfone, polyetherimide, polytetrafluoroethylene, polyethylene glycol, polypropylene glycol, copolymers thereof, or blends thereof.

[0035] Generally, the compositions described herein contain an aqueous solvent, an organic solvent, or a combination thereof. Desirable solvents include those in which the photo-oxidation-reduction active component and optional optically inert material can be dissolved or dispersed. Preferably, the solvent system involves a solvent having a high solubility / dispersibility for the optically inert material and another solvent having a high solubility for the photo-oxidation-reduction active component.

[0036] III. Methods of Preparation and Reagents Thereof

[0037] The compositions described herein are generally prepared by mixing two or more components. Specific, non-limiting procedures are provided in the Examples section below. Preferably, when an optically inert material is present, the composition is saturated with the optically inert material in order to increase the speed of phase separation and / or molecular aggregation.

[0038] IV. Methods of use

[0039] The disclosed compositions and methods can be used to fabricate products by three-dimensional printing. The method involves exposing the composition to a light source. In the most preferred form, the three-dimensional printing does not involve extensive covalent crosslinking of the composition, where extensive covalent crosslinking refers to 40% to 100% (such as 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc.) of the composition undergoing covalent crosslinking upon exposure to the light source.

[0040] The disclosed compositions and methods can be applied to new technologies involving direct laser printing in commercial strategies that traditionally rely on photoreduction or photopolymerization. However, as noted above, both of these reactions are limited by the printable materials. In addition, photoreduction is only applicable to metal printing, and photopolymerization is highly dependent on the presence of photoresist materials. The disclosed compositions and methods can be applied to general material printing and printing structures with smaller feature sizes. The disclosed compositions and methods can be used to directly print electronic devices with existing commercially available laser 3D nanoprinters, avoiding the need to modify existing 3D printing platforms. The disclosed compositions and methods allow for direct 3D printing of functional electronic devices with multiple components.

[0041] Preferably, the light source intensity is between 1 µW and 500 µW, such as 5 µW, 8.32 µW, 10 µW, 15 µW, 18 µW, 20 µW, 25 µW, 30 µW, 35 µW, 50 µW, 75 µW, 100 µW, 150 µW, 165 µW, 166.4 µW, and 200 µW, etc. In some forms, the light source is a laser. In some forms, the light source is applied by a focused exposure method, a region of interest exposure method, a single point exposure method, etc. In some forms, the product is a biomedical device, an electronic device, an electronic paper display, an organic electronic element, a conductive nanowire, a field effect transistor, a material for optical camouflage, a smart window (e.g., for building thermal management), etc. In some cases, the composition can be used to generate an array of microwires (e.g., an array of biomolecular microwires), which can be further designed as a microchip for biosensors or detection. In addition, by combining the patterns of conductive nanowires and organic field effect transistor polymer nanowires, nanoscale integrated circuits can be generated. The dimensions of the product can be between 50 nm and 1000 µm, 50 nm and 1,000 nm, 50 nm and 750 nm, 50 nm and 500 nm, or 100 nm and 500 nm, such as 200 nm, etc.

[0042] Examples

[0043] Phase transitions are universally observed in materials and living matter, where molecular interactions dictate the formation of phases and their properties. The ability to control such interactions would be beneficial for the production of phase transitions on demand and materials with new responsive properties. While such control is typically exercised by well-recognized molecular forces, dissipative chemical reactions can induce effective interaction potentials and phase transitions, phenomena that have been scarcely investigated. The work below shows that the photochemical electron shuttling process in photoredox reactions induces substantial apparent attractions between molecules without causing net chemical reactions, which leads to Avrami-like aggregation and phase transitions. More importantly, photoredox reaction solutions can act as non-equilibrium molecular baths, allowing any immersed inert material (e.g., colloids and solute molecules) to partially inherit the bath's active behavior, thereby inducing similar attractive potentials and leading to photoinduced aggregation and phase separation of the immersed passive cargo in general. With such versatility, photoredox inks can be formulated for 3D laser direct writing, allowing the printing of a wide variety of materials, including biomolecules and organic electronic materials, with a resolution of ~100 nm. Here it is shown that proteins, DNA nanostructures, and functional nanoscale organic electronic elements, including conducting nanowires and field effect transistors, can be directly fabricated from photoredox inks.

[0044] Surprisingly, simple photoredox reactions with forward electron transfer and reverse recombination can generate effective non-equilibrium baths 17 which induce apparent attractive potentials between the reactants and immersed inert colloids and solute molecules. As a result, photoredox solutions act as active media under much milder conditions compared to their solid-state counterparts, where universal photoinduced aggregation of any immersed cargo, ranging in size from molecules to microns, can be achieved. In combination with laser direct writing strategies, such photoinduced phase separation phenomena can serve as a new three-dimensional (3D) nanofabrication method that, in principle, can directly laser print functional nanodevices with versatile materials 18,19 . To demonstrate its applicability, photoredox active inks for 3D printing were formulated with biomolecules and organic electronic polymers. Functional nanoelectronic device components, including conducting nanowires and field effect transistors, were realized with such new technology.

[0045] Example 1: Photoinduced molecular aggregation and phase separation of D5 molecules under patterned laser scanning

[0046] Materials and Methods

[0047] The commercial D5 (3-(5-(4-(diphenylamino)styryl)thiophene-2-yl)-2-cyanoacrylic acid) organic dye and BQ (1,4-benzoquinone) were purchased from a chemical company and used without further purification. In the classical method, 10 μΐ of a saturated D5 (250 μΜ) acetonitrile (MeCN) solution was mixed with 40 μΐ of a saturated BQ (40 mM) MeCN solution and injected into a glass tube. Using the region of interest (ROI) scan or the spot bleaching mode scan of a commercial confocal microscope (TCS SP8, Lecia), fluorescence images of the D5 dye were taken after a fast bleaching fast step and repeated for a long time. A series of irradiation intensities and concentrations of BQ quencher molecules were tested, respectively. For the irradiation intensity experiment, the laser power at 488 nm was set to 8.32 to 75 μW. And, the concentrations of BQ tested were 9.5 to 30 mM.

[0048] Results

[0049] The photoinduced electron transfer (PET) process involves the transfer of an excited electron on a donor molecule to an acceptor upon photon absorption, resulting in a redox reaction. This process is mainly present in many dye quencher systems and is widely used in organic photosynthesis 20 . A famous application of the PET method in energy applications is the dye-sensitized solar cell (DSSC) 21 , where the photoredox reaction on the photoanode is balanced by the reverse reaction on the counter electrode, thus converting light into electricity. In DSSC, the overall electron transfer chain is from the counter electrode, through the redox shuttle and the dye molecule, and finally to the TiO2 conduction band, as shown by the red arrow in Figure la. It is well known that photoexcited electrons, in addition to preferentially transferring to the TiO2 conduction band, can also transfer back to the LUMO of the redox shuttle if not collected quickly, which is an energy loss process called electron recombination 22 , as shown by the blue arrow. Such electron recombination is undesirable and has been minimized by optimizing the electronic structure of the redox shuttle. However, it is prudent to inquire about the details of the free energy thermalization in such recombination processes, as there is a fierce debate about whether energy dissipation at the molecular level can produce some mechanical effects 23-26 .

[0050] In this study, it was found that by intentionally using a redox shuttle with a high electron recombination rate, the photoredox electron cycle highlighted in the dashed blue rectangle in Figure la can induce an apparent attractive potential of the reactant molecule, leading to aggregation and phase transition in the active molecule system, as shown in Figure lb.

[0051] In principle, many fluorescent dyes can be used as photosensitizers to construct a photoredox system, and specifically the 3-(5-(4-(diphenylamino)styryl)thiophene-2-yl)-2-cyanoacrylic acid (D5) dye was chosen as a model photoredox donor 27 , and benzoquinone (BQ) and naphthazarine were chosen as redox shuttles with high recombination rates to provide electrons to the D5 dye at the charge separation step, and also to accept electrons from the excited D5 in the regeneration step.

[0052] As shown in Figure 1c, a mixed solution of D5 (0.1 mM) and BQ (24 mM) was selectively irradiated with a 488 nm laser within the red circle. Before excitation, the fluorescence intensity was uniformly distributed across the observation area, confirming that the system was a homogeneous single-phase solution. During the 80 seconds of laser excitation (69 kW / cm 2 ), the fluorescence intensity within the irradiated area gradually increased more than 10 times compared to the background. Such an intensity enhancement is in stark contrast to the photobleaching 28 of fluorescence commonly observed, indicating an unexpected photoredox-induced aggregation. Taking advantage of such a phenomenon, one can pattern arbitrary concentration configurations (such as the university abbreviation “HKU”) in solution with a scanning laser, as shown in Figure 1d.

[0053] A closer examination of such aggregation with the fluorescence intensity evolution reveals that the aggregation has an incubation phase. As shown in Figure 1e, an incubation of about 10-20 seconds is required before the fluorescence intensity increases almost linearly with time and reaches saturation, and such aggregation is apparently intensity-dependent, where higher irradiation intensity leads to faster and more intense aggregation.

[0054] It is worth noting that such observed photo-induced aggregation is related to the photoredox reaction, rather than the temperature gradient in thermophoresis previously reported 11,29,30 . To confirm, a pure dye solution was used as a control, where the light absorption, and thus the local temperature increase caused by the laser, hardly changes. Since no aggregation was observed in this control experiment, the molecular aggregation is indeed induced by the photoredox reaction.

[0055] To investigate the kinetics of the aggregation process, the fluorescence intensity information must be converted into the relative concentrations of dye and redox shuttle. Time-correlated single photon counting (TCSPC) lifetime spectroscopy was used to independently track the concentrations of D5 and BQ during excitation. As shown in Figure If, the PET method quenches the fluorescence emission of D5 as the concentration of BQ is increased from 0 to 1.4 mM, and the lifetime decreases from 820 ± 80 ps to 280 ± 30 ps. Since both the fluorescence intensity and lifetime follow a Stern-Volmer relationship, the D5 / BQ PET is a dynamic quenching process, i.e., the charge transfer complex is formed from an excited D5 molecule. In this aggregation experiment, the weak laser from the TCSPC system is focused in the redox-active solution while measuring the fluorescence lifetime of D5 during the aggregation process. Although the relative fluorescence intensity increases, the lifetime of D5 changes little, which can be converted into the relative concentrations of dye and redox shuttle using a Stern-Volmer relationship. As shown in Figure Ig, although the irradiation intensity is much weaker in the TCSPC system, the aggregation of D5 can be observed while the concentration of the redox shuttle BQ is mostly undisturbed. This indicates that the photoredox-induced aggregation mainly concentrates the active D5 molecules rather than the redox shuttle, which allows us to directly use the irradiation intensity as a benchmark for the relative dye concentration.

[0056] Based on the TCSPC measurements, here, it is assumed that the photoredox-induced aggregation consists of four sub-reaction steps:

[0057] (1) photoexcitation:

[0058] (2) charge transfer:

[0059] (3) charge recombination:

[0060] (4) aggregation:

[0061] where the dye molecule D5 is first photoexcited (1) and forms a metastable complex with BQ through charge transfer from the excited molecule (2), which can relax back to the initial state through charge recombination (3). Such a reversible photoredox dissipation of the complex structure induces aggregation (4), which can be considered as a classical nucleation and growth in phase separation.

[0062] Such kinetics can generally be explained by the classical Kolmogorov-Johnson-Mehl-Avrami (KJMA) model 31,32 which assumes a random and constant generation of nucleation centers and linear aggregation growth. In this model, the normalized dye concentration can be fitted as

[0063]

[0064] where n is the Avrami factor, is the characteristic transformation rate constant related to the particle interaction and concentration. Both n and K reflect the nucleation and growth mechanism in the sample. For the Avrami factor, the equation is

[0065]

[0066] where a is the nucleation exponent (a = 0 for 0 nucleation rate and a = 1 for constant nucleation rate), b is the dimension of growth, and c is the growth exponent (c = 1 for interface-controlled growth and c = 0.5 for diffusion-controlled growth). By reconfiguring the KJMA equation (1) to express ln [-ln(1 - C D5 )] as a function of ln(t), the slope n = 4 is obtained (Supplementary Information Figures S3a and b), and a = 1 and bc = 3. This result corresponds to uniform 3D nucleation and growth controlled by interface reaction 33 . For the transformation rate constant K, the general equation is

[0067]

[0068] where K0is the isothermal JMAK parameter representing the rate constant K at infinite temperature, E eff is the effective activation energy describing the energy barrier of the phase transition, T is the absolute temperature, and k B is the Boltzmann constant.

[0069] As shown in Figure le, the light-induced aggregation kinetics of various irradiation powers follow the KJMA rate law, while the transformation rate constant K increases with the input laser power and follows the law. This observation indicates that, assuming the light-redox-induced aggregation follows the JMAK mechanism, the effective activation energy barrier E eff will linearly decrease with the irradiation intensity, as shown in the inset of Figure le, which is also consistent with the previous observation in the photoactive colloidal reaction system 16 .

[0070] In addition, since the kinetics of aggregation is closely related to the photo-redox reaction, the growth rate of aggregation can also be adjusted by the redox shuttle concentration. As shown in Figure If, the transformation rate constant K exhibits a clear dependence on the benzoquinone concentration [BQ], with the proportionality K ~ [BQ] 4 . This indicates that the redox shuttle concentration does not change the effective activation energy barrier, but rather influences the isothermal JMAK parameter K0with the Avrami factor n = 4, which can be reasonably attributed to the reaction-limited growth mechanism.

[0071] Example 2: Measuring the force on a silica probe in a photoredox bath using optical tweezers

[0072] Materials and Methods

[0073] For optical tweezers force measurements based on QPD (position-sensitive quadrant photodetector), an Olympus Ix81 inverted microscope with a 60x / 1.4NA oil immersion objective was used in conjunction with a 1000 mW 1064 nm NIR laser system to create a dual-well optical trap and a position-sensitive sensor, digitized at a sampling frequency of 50 kHz. In the classic measurement process, 2 μm SiO2 particles were used as passive tracer probes, and the wave dynamics generated by the active molecules on the probes in the photo-redox system were measured under uniform 465 nm LED structured light illumination. The force applied was 0 to 5.96 W / cm² in a MeCN solution containing 100 μm D₅ and 5 mM naphthylazine. 2 A series of irradiation intensities were applied. To avoid interaction with other particles and substrates, the silica probe was placed in the middle of the solution. First, the trap stiffness was calibrated using a wave power spectrum analysis method at the silica body position under light-free illumination. and Through equations Further calculation of the force signal of the probe. Finally, the force spectrum was calculated using the Welch method. The Hamming window sampling was set at 50 kHz. For size-dependent experiments, a series of 0.5–5 μm silica probes were measured in a photoredox bath.

[0074] For the attraction force measurement, a 3 μm silica bead was captured by optical tweezers that were fixed in the middle of the solution and adjusted. Then, another silica bead was clamped using another channel of the optical tweezers to approach the first silica bead and the force between them was measured.

[0075] result

[0076] While the exact mechanism of photoredox-induced aggregation in this system requires further investigation, it is believed that electron shuttle in the PET process may power molecular movement, with active molecules aggregating due to enhanced mobility and apparent attraction. In active colloidal systems, the active component is a self-propelled particle that can transfer activity fluctuations to embedded passive particles. 36 This leads to enhanced apparent diffusion. 37,38 Assembly 39,40 and gathering 41 At the molecular level in living cells, this type of bioactive assisted assembly is ubiquitous, where motor proteins provide the active environment that allows for the dynamic assembly of protein clusters and microtubules. 42-44. Here, it is tested whether the active environment provided by the photoredox reaction can effectively induce the assembly of a submerged passive cargo at the microscopic scale.

[0077] Here, the interaction under uniform illumination is investigated using inert silica particles immersed in a photoredox solution with D5 and naphthazarine shuttles. As shown in Fig. 2a, upon illumination, the dispersed silica colloids gradually assemble into close-packed crystals, suggesting evidence of apparent attractive interactions between colloids. Of note, while such observed active crystallization is reminiscent of the previously observed active particle aggregation 14,45-47 Similar, but the underlying mechanism is different, as the previous active particle aggregation was formed from reaction-induced hydrodynamic flows, while in the composition and method described in this example, the particles are passive cargo with inter-particle attraction mediated by the active molecular species in solution.

[0078] Conceptually, when inert particles are immersed in an active environment, the random noise of active molecular collisions leads to enhanced fluctuations beyond the scope of the Boltzmann distribution. To extract such active fluctuations, optical tweezers are used to trap and measure the force spectrum of a submerged silica bead probe in a photoredox solution 48 . As shown in the force spectrum in Fig. 2b, higher illumination intensity corresponds to higher photoredox activity, leading to enhanced fluctuations of the probe particle across the entire spectrum. The active energy is integrated over the entire frequency of the force spectrum by the following equation: The value of the dissipation rate J estimates the average rate of energy transfer from active molecules to the tracer colloids, manifested as translational fluctuations 49 . Remarkably, J increases substantially as the illumination intensity increases to 6.0 W / cm 2 (the intensity of active molecular collisions induced by the photoredox reaction), which is indicative of the enhanced fluctuations of the inert silica particles. To further quantify the diffusion enhancement dependence of the inert silica particles, the Langevin equation is adopted to model the random forces acting on these particles. That is, the position of the probe particle r(t) is governed by

[0079]

[0080] its equilibrium deterministic frictional and optical trapping forces with random active and thermal forces. In Eq. (4), κ is the optical trapping stiffness, γ is the friction coefficient of the stokes drag, D eff is the effective diffusion coefficient of a zero-mean, δ-correlated Gaussian white noise process In the active Brownian system, the effective temperature T eff of the colloids can be simplified from the analogous equilibrium state of Eq. 48 ​Higher effective temperatures correspond to the case where the photo-redox bath "heats" the probe particles by bombardment from the active environment, allowing the particles to fluctuate dramatically in their actual temperature. As shown in Figure 2c, for particles of different sizes, the effective temperature is proportional to the irradiation intensity T. eff ~I 2 Since the efficiency of energy transfer is size-dependent, smaller probe particles exhibit higher effective temperatures than larger probe particles. An inset in Figure 2c shows 6 W / cm². 2 T under irradiation eff Larger particles exhibit significantly lower T values ​​than smaller particles. eff This phenomenon provides a visual physical picture to reasonably explain the colloidal crystallization observed in Figure 2a: due to the increase in physical size, all the “hot” particles condense into the “cold” clusters, and individual colloids exhibit a higher effective temperature than the colloidal clusters.

[0081] In active material systems, it is well known that active mobile particles undergo migration-induced phase separation (MIPS). 51-53 Self-separation into a dilute phase and a concentrated phase. The physical picture of MIPS can be described as active particles accumulating where they move slowly, forming a positive feedback loop where the increased local density leads to a further reduction in particle mobility and induced phase separation. Most examples of reduced mobility are primarily due to particle collisions. 52 or density-dependent velocity distribution 53 The resulting velocity rearrangement leads to this. However, in active molecular systems, the size dependence of the effective temperature provides a new perspective for understanding phase separation, where particle aggregation and cluster growth lead to the cold process of the colloid (Fig. 2d). This MIPS can be balanced using repulsive forces. 54,55 The repulsive force can be measured by capturing two probe particles with dual-beam optical tweezers. As shown in Figure 2e, the net apparent attractive force is experimentally observed by subtracting the net interparticle force without illumination from the force with illumination. 54 As shown in Figure 2e, the apparent attraction potential (E) attr The intensity increases linearly with increasing irradiation intensity. When the irradiation intensity exceeds 0.8 W / cm²... 2 At that time, E attr Suppressing thermal energy k B T makes it possible for passive particles to aggregate in a photo-oxidation-reduction bath.

[0082] Example 3: Photoinduced aggregation and phase separation of tracer particles

[0083] Materials and Methods

[0084] Similar to the light-induced molecular aggregation and phase separation experiments of D5 molecules, the ROI bleaching scan mode was applied in the tracer particle aggregation and phase separation experiments. In the classical experiments, tracer particles were added to 50 μΜ D5 and 16 mM BQ acetonitrile solutions. The tracer particles selected were 500 nm silica colloids, 100 nm gold nanoparticles, 10 nm CdTe quantum dots, and 2 nm FITC molecules. In the FITC molecule phase separation experiments, irradiation intensities from 0 to 75 μW were tested. In the BSA phase separation experiments, 0.5 mg D5, 2 mg BQ, and 0.5 mg BSA were added to 500 μΐ acetonitrile. The BSA was dissolved in a 500 μΐ DMSO and 500 μΐ H2O mixed solution and filtered with a 220 nm Nelon filter. The transparent solution was then injected into the glass tube under the spot bleaching mode scan.

[0085] BSA was dissolved in a 500 μΐ DMSO and 500 μΐ H2O mixed solution and filtered with a 220 nm Nelon filter. The transparent solution was then injected into the glass tube under the spot bleaching mode scan.

[0086] Results

[0087] As shown in Fig. 2c, the smaller the particle, the more obvious the effective temperature. It is reasonable to extrapolate this trend to even smaller passive cargo units, even at the molecular level. Since smaller cargos can diffuse faster, it is assumed that a higher effective temperature leads to a stronger cooling process, a trend of aggregation formation, which not only leads to light-induced aggregation from microns to nanometers, but also leads to phase transitions of molecular species.

[0088] Here, a series of inert cargo units with different sizes and surface properties were selected, from 500 nm insulating silica microbeads to 100 nm metallic gold nanoparticles, to 10 nm semiconductor CdTe quantum dots, and finally to fluorescein molecules. None of these units showed light-induced aggregation without a photo-redox bath, showing the passive nature of these cargos. As shown in Fig. 3a, immersed in a photo-redox solution, all inert cargos gradually aggregated into the laser scanning area (red circle). These results demonstrate the generality of using a photo-redox bath as an active bath to concentrate the immersed cargo by photoexcitation. The light-induced aggregation process of these passive cargos can also be analyzed using the KJMA model, similar to the photoactive dyes described in the previous sections. Through similar analysis results, it is shown that passive cargo molecules can partially inherit the active behavior of photoactive dyes 41,57 , which means an effective momentum transfer process from photoactive dyes to immersed cargos.

[0089] One interesting observation in the molecular cargo (fluorescein) aggregation experiment is that the fluorescence intensity of fluorescein will reach a peak under strong light (75 μW) and decay as the irradiation time is prolonged. Similar phenomena are observed for CdTe quantum dots. Brightfield images show that a dark solid precipitate gradually grows in the center of the irradiation area as the irradiation time is prolonged (Fig. 3b), which indicates that the aggregation process will concentrate the passive cargo beyond the saturation limit, leading to precipitation, the same as the CdTe cargo system.

[0090] Due to its generality, the disclosed compositions and methods facilitate phase separation with light guiding of any selected material, which has great applicability in the new biomedical and electronic device 3D printing manufacturing. By tuning the protein-protein and light interactions, such light-activated phase separation in life systems has been previously demonstrated in cells with optogenetic tools 4,58-60 Here, laser-induced phase separation of biomolecules is tested using the compositions disclosed herein. Bovine serum albumin (BSA) is first selected as a model system to show the applicability of protein deposition. As shown in Fig. 3d, upon laser irradiation, a solid BSA precipitate is gradually concentrated from solution by focusing a 166.4 μW 488 nm laser on the substrate. The resulting concentrated BSA is assumed to be a stagnant gelled precipitate, as the deposit does not quickly re-dissolve into solution after the irradiation is turned off. Such a gelling process can be attributed to the strong aggregating power of the photo-redox bath, which drives the system deep into the phase boundary and passes the gelation point 4,61 Since such observed light-induced aggregation and phase transition originate from the active bath, in principle, general light-guided deposition can be achieved for any immersed ingredient / solute, which indicates that active inks compatible with any material can be formulated for laser direct 3D micro-printing.

[0091] Example 4: Direct laser printing of biomolecules

[0092] Directed laser printing of biomolecules is first tested in a Leica TCS SP8 confocal microscope with a 40 x 0.85 NA objective using single-photon laser. The printing uses a point-bleaching mode, where each bleaching spot is exposed with an 18 μW 488 nm laser for 25 seconds at a time for one layer of printing. Then, the lens is adjusted to be 1.5 μm away from the printed layer for the next layer of printing. By the same method, the bleaching spots are reduced for each layer, and a DNA nanowire array is printed.

[0093] For two-photon 3D laser printing, a commercial two-photon printer (Photonic Professional GT2, Nanoscribe) with a 63x oil objective was used for 3D directed laser printing. To increase the attachment of DNA microstructures to glass, the substrates were modified with positively charged polymer (poly(diallyldimethylammonium chloride)) by a layer-by-layer approach. Static mode and pulsed laser printing methods were employed for 3D microfabrication. For each spot exposure with BSA ink, the laser power was set to 30% of the maximum power for 0.15 s, and the gap for each printing spot was set to 0.2 pm for x, y, and z axes. But the parameters for DNA ink were slightly changed, such as 20% of exposure power and 0.2 s of exposure time. After printing, the microstructures were washed with a DMSO and H20 mixed solution (volume ratio = 1 : 1) to remove the excess ink, and then they were immersed in a pure DMSO solution. Then, the pure DSO solution was replaced with a gradient ethanol and H20 mixed solution with a volume ratio of 0% to 100% in an exchange process. Finally, critical point drying (EM CPD 300, Leica) was used to remove ethanol without damaging the 3D microstructures.

[0094] Results

[0095] Direct laser writing (DLW) is one of the most promising 3D printing techniques, capable of rapidly fabricating high-resolution nanodevices prototypes 62 , in which electronic 18,63,64 , optical 18,63,64 and mechanical 65 microdevices have been demonstrated. However, photo-crosslinking is generally considered necessary for laser writing, allowing the precursors in the ink to solidify into the desired nanostructures. As a result, specially designed photo-curable materials have been developed to accommodate the DLW method 18,66-68 .

[0096] The photo-redox-induced phase transition demonstrated in the disclosed compositions and methods provides an alternative physical method in which deposition is caused by an active bath that over-saturates the desired material at its phase transition boundary. As shown in FIG. 4a, by scanning a focused laser beam in a photo-redox bath of mixed loading materials, desired 3D nanostructures of the corresponding material can be prepared. For example, after a single spot exposure of 75 s, vertical BSA nanowires with a diameter of 1.5 pm and a length of 7.2 pm can be deposited on a glass substrate (FIG. 4b, left, middle, and supplemental information FIGs. S7a and b). In addition to the central vertical nanowire, the diffraction rings corresponding to the point spread function of the focused light around the nanowire are also visible, indicating that the resolution is diffraction-limited rather than measurement method-limited. As shown in the right panel of FIG. 4b, the characteristic of 1672 cm 69 corresponding to the white protein amide I band peak -1Raman microscopy images at the peaks (Supplementary Information Figure S8) are consistent with the deposited nanowires, confirming that the deposition is indeed of the BSA protein.

[0097] To further improve the resolution, a commercial two-photon laser printer (Photonic Professional GT2, Nanoscribe) was used with reactive inks without further modification of the instrument. Here, an 850 nm femtosecond laser was used to excite the dye molecules, while BSA and salmon DNA were used to show the applicability of nanometric precision 3D bioprinting. In this experiment, the biomolecules were dissolved in a water / DMSO mixed solution and solubilized with a photo-oxidation-reduction dye / shuttle agent. As shown in Figure 4c, the BSA-printed nanometer antenna, nanometer pyramid, nanowire array and the salmon DNA-printed double helix, vertical nanowire in Figure 4d were successfully produced with two-photon excitation in which sub-100 nm structures can be resolved.

[0098] Example 5: Nanoelectronic device printing

[0099] Materials and methods

[0100] First, the n-type silicon wafer coated with a 300 nm SiO2layer was cleaned in Piranha solution (component volume ratio H2SO4 / H2O2= 70:30) by heating at 110 °C for 2 hours and then thoroughly rinsing with deionized (DI) water. On the clean silicon wafer, 5 nm Al2O3, 5 nm HfO2and 10 nm Al2O3thin films were sequentially deposited by atomic layer deposition (ALD) at 150 °C, with deposition cycles of 56, 40 and 111 for each layer, respectively.

[0101] Second, gold microcircuitry was fabricated on the silicon wafer using ultraviolet lithography. I-line photoresist was coated and exposed on the wafer as a sacrificial layer by the designed pattern. After removing the photoresist in the exposed area, 50 nm Au thin layer was deposited by thermal evaporation at a pressure of 5 x 10 −4 Pa, at a rate of 0.1 Å / s, and ultrasonically treated in acetone solution for 15 minutes to remove the excess I-line.

[0102] For PEDOTS:PSS printing ink, 0.5 mg D5 and 2 mg BQ were dissolved into 100 μΐ DMSO mixed with 100 μΐ 1.1 mg / ml PEDOTS:PSS aqueous solution. The ink was then injected into a channel sealed by glass with scotch tape on a gold microcircuit. Nanowires of PEDOS:PSS were printed by line bleaching mode with 18 μ\Λ of 488 nm laser from 45 seconds to 540 seconds. Similarly, P3HT ink consists of 0.5 mg D5, 2 mg BQ and 0.5 mg P3HT in a mixture of CHCI3and DMSO. Nanowires were also printed by line bleaching mode with 75 μ\Λ of 488 nm laser from 10 seconds to 40 seconds.

[0103] Results

[0104] In view of the generality of the disclosed method (e.g., photoredox-induced DLW method) and the wide selection of solution-processed electronic materials, it is possible to laser direct write functional electronic components with high precision.

[0105] Generally, electronic devices are composed of conductive, semiconductive, and insulating materials that are appropriately overlapped and interconnected. Previous DLW techniques require photo-curable ligands or adhesives, which can deteriorate the electronic properties of the deposited materials 70-72 . Here, using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOTS:PSS) as a representative conductive polymer and poly(3-hexylthiophene) (P3HT) as a representative semiconductive polymer, the suitability of photoredox-induced deposition for electronic component fabrication was demonstrated.

[0106] PEDOT:PSS and P3HT are the most studied solution-processed electronic polymers, which have been extensively chemically modified and engineered 73-77 . In this test, PEDOTS:PSS and P3HT active inks were similarly prepared, where the electronic polymers were dissolved in a photoredox-active base solution and directly used for DLW. By scanning a 488 nm laser on a silicon substrate with 300 nm thermal oxide, nanowires of the respective polymers could be deposited, bridging two gold electrodes (Figure 5a). As shown in Figure 5b, -800 nm wide PEDOT:PSS and P3HT nanowires were deposited from the formulated active inks, bridging a 10 μιη gap after 40 seconds of exposure. PEDOT:PSS nanowires were tested with two-terminal I-V measurements to determine the conductivity, while P3HT nanowires were tested as field effect transistors with the bottom silicon as a global gate.

[0107] As shown in Figure 5c for PEDOT:PSS and Figure 5d for P3HT, classic metal and semiconductor I-V transfer curves can be obtained for all deposited nanowires with different exposures. By increasing the exposure dose, the nanowire thickness increases proportionally, and the resulting PEDOT OS:PSS nanowire conductivity increases from 10 2 S∙m -1 to 10 3 S∙m -1 and approaches the conductivity of previously reported pristine PEDOT OS:PSS nanowires 78-80 . For P3HT-based field effect transistors, the device mobility reaches 4.1◊10 −4 cm 2 V −1 S −1 at an on / off ratio of 1.2 x 10 3 , which is also 10 times higher than previous nanowire FET measurements 81-83 .

[0108] It is noteworthy that the method of printing organic electronic elements described herein provides much higher resolution than previous inkjet methods, which guarantees improved performance of integrated organic electronic devices by reducing device size. One drawback of such photo-redox-induced deposition is that the printing speed is limited by the phase transition and material diffusion processes in solution and is currently slower than using existing photo-curable inks. A potential solution to this challenge is to formulate active inks with concentrated precursors and additional ingredients to approach the phase transition boundary, which facilitates phase transition and deposition at lower irradiation. Furthermore, since such new methods significantly expand the list of printable materials without the need for instrument modifications, they can be integrated into existing device printing processes to make functional components or modifications on pre-printed photo-curable resins, thereby enhancing device functionality.

[0109] General Materials and Methods

[0110] i. Ultraviolet-visible absorption and fluorescence spectroscopy measurements

[0111] Ultraviolet-visible absorption measurements of solutions were determined with an Agilent Cary 60 spectrophotometer. Ultraviolet-visible absorption spectra of D5 solutions were collected from acetonitrile solutions at low concentrations. For fluorescence spectroscopy measurements, D5 FITC and CdTe were dissolved in acetonitrile solutions and measured by a Shimadzu RF-6000 fluorescence spectrometer.

[0112] ii. Time-correlated single photon counting (TCSPC) measurements

[0113] The fluorescence lifetime of D5 dye was determined on the nanosecond time scale by TCSPC technique with an Edinburgh FLS1000. A picosecond pulsed diode laser (450 nm, 20 MHz) was used as excitation source. A photomultiplier tube (PMT-900, 200 nm - 870 nm, lifetime range: 100 ps to 50 μβ) was used to detect the fluorescence photons with an emission wavelength set to 610 nm with a band gap of 2 nm. The decay of 2000 counts was recorded in peak channel within a time window of 50 ns. Data were collected and analyzed using Fluoracle software based on iterative deconvolution of the data with the instrument response function (IRF). In a classical fluorescence lifetime measurement, 1 mL of a 0.1 mM D5 and 1 mM Bq acetonitrile solution was placed in a quartz cuvette (10 mm path length), sealed with a Teflon stopper and mounted on the device. The Stern-Volmer relationship of D5 and BQ was investigated by changing the concentration of BQ from 0 to 1.4 mM by setting a constant count value (2000). In addition, the concentration change of D5 and BQ over time was measured by setting a fast measurement time (30 seconds) after a long time continuous irradiation time (2 minutes).

[0114] iii. Confocal-Raman spectroscopy scans

[0115] Raman spectra were collected using a WITec Alpha 300 R confocal Raman microscope (100X objective, 0.9 NA) with excitation wavelengths of 532 nm for BSA, 633 nm for DNA, and 783 nm (off-resonance conditions) for PEDOT:S:PSS and P3HT. Spectra were taken at room temperature in the Stokes region and calibrated against the 520.5 cm −1 -1 line of an internal silicon wafer. The signal-to-noise ratio was enhanced by repeated acquisition.

[0116] iv. Device characterization

[0117] The OFETs were characterized with a Perfict Lab probe station with two Keithley 2635B system source meters, where the source and drain contacts were connected with low noise shielded probes and the gate connection was made with a probe chuck.

[0118] The transistor characteristics were obtained at room temperature in air by a standard probe station and two semiconductor parameter analyzers. The mobility of the devices was calculated in the saturation regime by standard methods:

[0119]

[0120] where W / L is the channel width / length and V G and V thVgand Vth, respectively. C i is the insulator capacitance per unit area.

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[0207] One skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments of the application described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

1. A composition comprising: (i) a photoredox active component comprising an electron donor and a redox shuttle, and optionally (ii) one or more photoinert materials.

2. The composition according to claim 1, wherein the electron donor comprises a photosensitizer.

3. The composition according to claim 2, wherein the photosensitizer comprises a photoredox active dye (e.g., a photoactivated fluorophore, such as a fluorescent dye).

4. The composition according to any one of claims 1 to 3, wherein it is in the form of a solution, suspension, colloid, gel, emulsion, etc.

5. The composition according to any one of claims 1 to 4, wherein it is in the form of a solution, suspension, gel, emulsion, etc.

6. The composition according to any one of claims 1 to 4, wherein the redox shuttle has a high electron recombination rate.

7. The composition according to any one of claims 1 to 6, wherein the redox shuttle comprises a halide redox shuttle, an organic redox shuttle, a transition metal complex redox shuttle, a tandem redox shuttle, or a combination thereof.

8. The composition according to any one of claims 1 to 7, wherein the redox shuttle comprises quinone (e.g., benzoquinone and dihydroxyanthraquinone), naphthalassium, dimethyl terephthalate, ferrocene, and (2,2,6,6-tetramethylpiperidin-1-yl)oxy radical (TEMPO) or a combination thereof.

9. The composition according to any one of claims 1 to 8, wherein the photoinert material is present and comprises synthetic polymers (e.g., solution-processable electronic polymers), natural polymers, thermoplastic polymers, nanoparticles, quantum dots, microparticles, biomolecules (proteins, DNA, etc.), and inert fluorescent dyes (e.g., fluorescein).

10. The composition according to any one of claims 1 to 9, comprising an aqueous solvent, an organic solvent, or a combination thereof.

11. A product obtainable from the composition of any one of claims 1 to 10.

12. A method of manufacturing a product, the method comprising three-dimensional printing, the three-dimensional printing comprising exposing the composition of any one of claims 1 to 10 to a light source.

13. The method of claim 12, wherein the intensity of the light source is between 1 µW and 500 µW, such as 5 µW, 8.32 µW, 10 µW, 15 µW, 18 µW, 20 µW, 25 µW, 30 µW, 35 µW, 50 µW, 75 µW, 100 µW, 150 µW, 165 µW, 166.4 µW, and 200 µW.

14. The method according to claim 12 or 13, wherein the light source is a laser.

15. The method according to any one of claims 12 to 14, wherein the light source is applied via a focused exposure method, a region of interest exposure method, a single-point exposure method, or the like.

16. The method according to any one of claims 12 to 15, further comprising agglomerating the components of the composition during and / or after exposure to the light source.

17. The method according to any one of claims 12 to 16, comprising an incubation period between exposure to the light source and aggregation of the components of the composition.

18. The method according to any one of claims 12 to 17, wherein the product is a biomedical device, an electronic device, an electronic paper display, an organic electronic component, a conductive nanowire, a field-effect transistor, a material for optical camouflage, a smart window (e.g., for building thermal management), etc.

19. The method according to any one of claims 12 to 18, wherein the size of the product is between 50 nm and 1,000 µm.

20. The method according to any one of claims 12 to 19, wherein the three-dimensional printing does not include a large amount of covalent crosslinking of the composition, wherein a large amount of covalent crosslinking means that 40% to 100% (such as 40%, 50%, 60%, 70%, 80%, 90%, or 100%) of the composition is covalently crosslinked after exposure to the light source.

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