An assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate

Abstract

The present invention relates to an assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate; the at least one circular polycrystalline colloidal monolayer comprises at least one type of uniformly sized particles arranged in juxtaposed single-crystalline domains that emit domain-specific structural colors when illuminated by a white light source. The present invention also relates to a method for preparing the assembly, as well as to the use of the assembly for labeling items of interest by direct deposition or, preferably, transfer onto a polymer film.

Description

[Technical Field]

[0001] The present invention relates to an assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate, the at least one circular polycrystalline colloidal monolayer comprising at least one type of uniformly sized particles arranged in juxtaposed single-crystalline domains that emit domain-specific structural colors when illuminated by a white light source. The present invention also relates to a method for preparing the assembly, as well as to the use of the assembly for labeling items of interest by direct deposition or, preferably, transfer onto a polymer film. [Background technology]

[0002] More and more brands, especially in the luxury goods sector and in the pharmaceutical and food industries, have to deal with counterfeiting and direct authentication of their products during resale between individuals and / or during use of the product by individuals.

[0003] Known solutions for labeling goods for authentication and anti-counterfeiting measures, such as methods related to laser coding and printing technologies, rely on deterministic principles and are therefore complex to implement but can be copied by counterfeiters. Conversely, methods that rely on stochastic processes allow very strong protection against duplication or counterfeiting by counterfeiters, but are difficult to implement and may not be suitable for easy authentication by consumers or end users.

[0004] Additionally, there is growing interest in systems that display complex patterns of structural color, not only as an anti-counterfeiting solution, but also for their visual and highly aesthetic aspects. Indeed, structural colors with their characteristic metallic aspects, reflective / diffractive rather than absorptive properties, and their light source-dependent variability convey to the objects with which they are associated particularly striking and visually pleasing qualities that are highly valued by consumers.

[0005] Therefore, there is a real need to develop novel identification marks that can be used to label goods and that can provide both a strong level of authentication for the primary user (producer, transporter or reseller) and a fast but reliable authentication for the end user (primary and secondary owner or consumer). The mark shall also present an aesthetic aspect and be visually pleasing to the consumer. Furthermore, the mark shall withstand external attacks, including washing, dropping or handling.

[0006] Surprisingly, we have discovered that assemblies comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate, exhibiting a unique pattern of multiple structural colors, achieve the aforementioned objectives. The assembly's unique geometric shape (a millimeter-sized circular monolayer) offers particularly advantageous portability, immediate implementation (due to being immobilized on a solid substrate), and easy detection of its unique photonic multicolor signature. The random juxtaposition of uniquely shaped domains exhibiting difficult-to-replicate and unprintable structural colors ensures strong unreplicability and inviolability, as well as visually arresting and enjoyable properties. Furthermore, because they are composed of self-assembled inert particles, they are environmentally friendly and their manufacturing methods do not generate waste. Detection can be performed using a simple white light source or ambient light (e.g., a cell phone), and users only need a magnifying lens to view the domains for proper pattern analysis and / or recognition.

[0007] Furthermore, the present assemblies can be easily realized on a wide range of solid substrates and particle types, and the circular polycrystalline colloidal monolayers can be easily embedded or transferred to another solid substrate without damaging the intrinsic pattern of the original assembly. Summary of the Invention [Means for solving the problem]

[0008] The present invention relates to an assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate; the at least one circular polycrystalline colloidal monolayer comprises at least one type of uniformly sized particles arranged in juxtaposed single-crystalline domains that are distinct from one another and randomly oriented relative to one another; the diameter of the circular polycrystalline colloidal monolayer is in the range of 0.25 to 2.5 mm.

[0009] In one embodiment, the diameter of the at least one circular polycrystalline colloidal monolayer ranges from 0.5 to 2 mm, preferably from 1 to 2 mm.

[0010] In one embodiment, the size of each single crystal domain is 100 to 100,000 μm 2 The range is.

[0011] In one embodiment, the core of the at least one uniformly sized particle is selected from inorganic materials, organic materials and mixtures thereof, preferably from silica, polymers such as pure polymers or polymers containing additives such as metal oxide inclusions, metals and mixtures thereof.

[0012] In one embodiment, at least one type of uniformly sized particle is intrinsically negatively charged or is surface modified, preferably with small organic or inorganic molecules, metals, linear polymers, branched polymers and mixtures thereof, more preferably with small negatively charged organic or inorganic molecules, negatively charged polymers and mixtures thereof.

[0013] In one embodiment, the assembly of the present invention comprises at least two circular polycrystalline colloid monolayers, which may be different or identical to each other, and the at least two circular polycrystalline colloid monolayers are arranged in an array, overlapping each other or not in contact with each other.

[0014] The present invention also relates to a method for preparing an assembly of the present invention, comprising the steps of: a) preparing an aqueous dispersion (A), at least one anionic colloidal particle having an average diameter in the range of 100 nm to 10 μm and a dispersity of less than 5% of the diameter, - at least one cationic surfactant at a concentration ranging from CMC / 10000 to CMC / 100, wherein the CMC is the critical micelle concentration of the at least one cationic surfactant; and -Aqueous medium preparing an aqueous dispersion (A) containing: b) depositing at least one droplet of the aqueous dispersion (A) prepared in step a) on the upper surface of a solid substrate, wherein the volume of the at least one droplet is 15 μL or less; c) protecting the upper surface of the solid substrate obtained in step b) from airflow and inverting the solid substrate upside down; d) maintaining the solid substrate in an upside-down position to evaporate at least one droplet of aqueous dispersion (A); and then e) optionally, flipping the solid substrate obtained in step d) into the correct orientation; The present invention relates to a method comprising:

[0015] In one embodiment, the contact angle of a droplet of the aqueous dispersion (A) prepared in step a) on the solid substrate is in the range of 20° to 120°, preferably 40° to 100°.

[0016] In one embodiment, the concentration of the at least one type of dispersed anionic colloidal particles ranges from 0.01 to 1 mg / mL, preferably from 0.02 to 0.8 mg / mL, more preferably from 0.04 to 0.6 mg / mL of aqueous dispersion (A).

[0017] In one embodiment, the concentration of the cationic surfactant ranges from CMC / 8000 to CMC / 500, preferably from CMC / 5000 to CMC / 1000.

[0018] In one embodiment, the method of the present invention further comprises, between steps c) and d), the step of injecting a further volume of aqueous dispersion (A) into the droplets of aqueous dispersion (A) inverted in step c).

[0019] In one embodiment, the method of the present invention further comprises, after step d) or optional step e), repeating steps b) to d), or optionally up to e), wherein a second droplet of aqueous dispersion (A) prepared in step a) is deposited either on top of or adjacent to, but not in contact with, the circular polycrystalline colloidal monolayer obtained in step d) or optional step e), and the volume of the second droplet of aqueous dispersion (A) is 15 μL or less.

[0020] In one embodiment, the method of the present invention comprises the steps of: f) preparing an aqueous dispersion (B) different from the aqueous dispersion (A), at least one anionic colloidal particle having an average diameter in the range of 100 nm to 10 μm and a dispersity of less than 5% of the diameter, - at least one cationic surfactant at a concentration ranging from CMC / 10000 to CMC / 100, wherein the CMC is the critical micelle concentration of the at least one cationic surfactant; and -Aqueous medium preparing an aqueous dispersion (B) containing: g) depositing at least one droplet of the aqueous dispersion (B) prepared in step f) either on top of or adjacent to, but not in contact with, the circular polycrystalline colloidal monolayer obtained in step d) or optional step e), wherein the volume of the droplet is 15 μL or less and the contact angle of the droplet on the solid substrate is preferably in the range of 20° to 120°; h) protecting the upper surface of the solid substrate obtained in step g) from airflow and inverting the solid substrate upside down; i) maintaining the solid substrate in an upside-down position to evaporate at least one droplet of aqueous dispersion (B); and then j) optionally, flipping the solid substrate obtained in step i) into the correct orientation; Further includes:

[0021] In one embodiment, step d) and / or optional step i) are carried out until the aqueous medium of the droplets of aqueous dispersion deposited in step b) and optional step g), respectively, has completely evaporated.

[0022] In one embodiment, optional step e) and / or optional step j) are carried out before the aqueous medium of the droplets of aqueous dispersion deposited in step b) and / or optional step g), respectively, has completely evaporated.

[0023] In one embodiment, the method of the present invention further comprises the step of transferring at least one circular polycrystalline colloidal monolayer obtained in step d) or any step e), i) or j) preferably to a polymer film.

[0024] The invention further relates to the use of the assembly of the invention for labeling articles of interest by direct deposition or, preferably, transfer onto a polymer film.

[0025] definition In the present invention, the following terms have the following meanings:

[0026] "Ambient temperature" refers to 20 to 25°C.

[0027] "Aqueous dispersion" refers to a system in which particles of one material are dispersed in water.

[0028] "Aqueous medium" refers to a solution in which the solvent is water.

[0029] "Average diameter" according to the present invention refers to the average diameter of the anionic colloidal particles present in the aqueous dispersion (A) or (B).

[0030] "Circular" refers to something having a circular shape, such as a disc or iris (ie, ring).

[0031] "CMC" or "critical micelle concentration" refers to the concentration for a given surfactant above which aggregates of surfactant molecules, e.g., micelles, form.

[0032] "Colloidal particles" refer to nanometer to micrometer spherical particles that can be dispersed in aqueous or organic solvents and do not dissolve in the substance.

[0033] "Colloidal monolayer" refers to colloidal particles arranged in a monolayer.

[0034] "Comprising" or "comprise" is to be interpreted in an open-ended, inclusive sense, including, but not limited to, In one embodiment, "comprising" means "consisting essentially of."

[0035] According to the present invention, the "contact angle" refers to the angle formed by the gas-liquid interface of a liquid, such as a droplet of distilled water or a droplet of aqueous dispersion (A) or (B), on a solid substrate. This quantifies the wettability of the solid substrate with respect to the liquid. The smaller the contact angle, the higher the wettability of the solid substrate, and when water is used as the liquid, the more hydrophilic the solid substrate is.

[0036] "Dispersity" is a measure of the size non-uniformity of particles. According to the present invention, the dispersity of anionic colloidal particles refers to the coefficient of variation of particle diameter (standard deviation divided by average diameter).

[0037] "Evaporation of droplets of aqueous dispersion" according to the present invention means evaporation of the aqueous medium of droplets of aqueous dispersion deposited on a solid substrate.

[0038] "From X to Y" refers to a range of values ​​between X and Y, where the limits of X and Y are included in the range.

[0039] "Polycrystalline" refers to a deposit having at least two single crystal domains randomly oriented relative to each other.

[0040] "Silicone" refers to an inorganic polymer containing chains of alternating silicon and oxygen atoms (the repeating unit is --Si--O--).

[0041] "Surfactant" defines a substance that reduces the interfacial energy between two liquids, between a gas and a liquid, or between a solid and a liquid. It often refers to an amphiphilic molecule that has two parts of different polarity: one lipophilic and low polarity, the other hydrophilic and high polarity. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 is a scheme showing the general process of how to prepare an assembly according to the present invention.

[0043] [Figure 2] FIG. 2 is a scheme illustrating one embodiment of the method according to the invention, which makes it possible to obtain circular polycrystalline colloidal monolayers in which the particles are separated by size.

[0044] [Figure 3] FIG. 3 is a scheme illustrating one embodiment of the method according to the invention, which makes it possible to obtain polycrystalline colloidal monolayers with the shape of an iris (ie a ring).

[0045] [Figure 4] 4 is a scheme illustrating one embodiment of the method according to the invention, which comprises the further steps f) to j), which makes it possible to obtain two polycrystalline colloidal monolayer disks of particles, the two monolayers being superimposed on each other.

[0046] [Figure 5A]Figure 5A shows a reflected light microscope image (scale bar: 200 μm) of polycrystalline colloidal monolayer disks of silica particles prepared by the method according to the present invention, where the average diameter of the silica particles is 0.56 μm (dispersity 3.6%) and the disks are immobilized on polystyrene, with a diameter of 750 μm. [Figure 5B] Figure 5B shows a scanning electron microscope (SEM) image (scale bar: 10 μm) of polycrystalline colloidal monolayer disks.

[0047] [Figure 6A] Figure 6A shows a reflected light microscope image (scale bar: 200 μm) of polycrystalline colloidal monolayer disks of polystyrene particles prepared by the method according to the present invention. The average diameter of the polystyrene particles is 4.65 μm (dispersity 2.6%), and the disks are immobilized on polystyrene. The diameter of the disks is 600 μm. [Figure 6B] Figure 6B shows a reflected light microscope image (scale bar: 200 μm) of a polycrystalline colloidal monolayer disk of silica particles prepared by the method according to the present invention. The average diameter of the silica particles in the disk is 2.4 μm (dispersity 1.7%), and the disk is immobilized on polystyrene. The diameter of the disk is 1000 μm. [Figure 6C] Figure 6C shows a reflected light microscope image (scale bar: 200 μm) of a polycrystalline colloidal monolayer disk of silica particles prepared by the method according to the present invention. The average diameter of the silica particles in the disk is 2.4 μm (dispersity 1.7%), and the disk is immobilized on polystyrene. The diameter of the disk is 500 μm. [Figure 6D] Figure 6D shows a reflected light microscope image (scale bar: 200 μm) of polycrystalline colloidal monolayer disks of silica particles prepared by the method according to the present invention, where the average diameter of the silica particles is 2.4 μm (dispersity 1.7%) and the disks are immobilized on untreated glass, with a diameter of 1000 μm.

[0048] [Figure 7]Figure 7 shows a reflectance microscope image (scale bar: 200 μm) of a polycrystalline colloidal monolayer of silica particles with an iris shape prepared by the method according to the present invention. The silica particles have an average diameter of 0.56 μm (dispersity 3.6%), and the monolayer is immobilized on polystyrene. The disk has a diameter of 850 μm and a central hole with a diameter of 350 μm.

[0049] [Figure 8A] Figure 8A shows a reflected light microscope image (scale bar: 500 μm) of a polycrystalline colloidal monolayer disk of silica particles prepared by the method according to the present invention, where the average diameter of the silica particles in the disk is 2.4 μm (dispersity 1.7%), and the disk is immobilized on polystyrene, with a diameter of 2100 μm. [Figure 8B] Figure 8B shows a reflected light microscope image (scale bar: 500 μm) of a polycrystalline colloidal monolayer disk of silica particles prepared by the method according to the present invention, where the average diameter of the silica particles in the disk is 2.4 μm (dispersity 1.7%), and the disk is immobilized on polystyrene, with a diameter of 400 μm.

[0050] [Figure 9] FIG. 9 shows a reflected light microscope image (scale bar: 200 μm) of polycrystalline colloidal monolayer disks of silica particles prepared by the method according to the invention, where the silica particles are separated by size (larger particles have an average diameter of 2.4 μm with a dispersity of 1.7% and smaller particles have an average diameter of 0.56 μm with a dispersity of 3.6%) and the disks are immobilized on polystyrene, with a diameter of 825 μm.

[0051] [Figure 10] Figure 10 shows a reflected light microscope image (scale bar: 200 μm) of two polycrystalline colloidal monolayer disks of silica particles prepared by the method according to the present invention, where the average diameter of the silica particles is 0.56 μm (dispersity 3.6%), the two monolayers are superimposed on each other and immobilized on polystyrene, and the diameter of the disks is 750 μm.

[0052] [Figure 11] Figure 11 shows a reflected light microscope image (scale bar: 200 μm) of two polycrystalline colloidal monolayer disks of silica particles prepared by the method of the present invention. The average diameter of the silica particles in the first disk is 0.98 μm (dispersity 2.7%), and the average diameter of the silica particles in the second disk is 0.56 μm (dispersity 3.6%). The two monolayers are superimposed on each other and immobilized on polystyrene. The diameter of the first disk is 1000 μm, while the diameter of the second disk is 800 μm.

[0053] [Figure 12A] Figure 12A shows a reflected light microscope image (scale bar: 200 μm) of polycrystalline colloidal monolayer disks of silica particles embedded in a NOA-based polymer slab, where the average diameter of the silica particles is 0.56 μm (dispersity 3.6%) and the diameter of the disks is 1250 μm. [Figure 12B] Figure 12B shows a scanning electron microscope (SEM) image (scale bar: 5 μm) of polycrystalline colloidal monolayer disks embedded in NOA-based polymer slabs.

[0054] [Figure 13A] Figure 13A shows a reflected light microscope image (scale bar: 200 μm) of a mold in a cured PDMS-based polymer slab of polycrystalline colloidal monolayer disks of silica particles, where the average diameter of the silica particles is 0.56 μm (dispersity 3.6%) and the diameter of the disks is 1000 μm. [Figure 13B] FIG. 13B shows a scanning electron microscope (SEM) image of the mold (scale bar: 5 μm).

[0055] [Figure 14A]Figure 14A shows a reflected light microscope image (scale bar: 200 μm) of a direct replica in a cured NOA-based polymer slab of polycrystalline colloidal monolayer disks of silica particles, where the average diameter of the silica particles is 0.56 μm (dispersity 3.6%) and the diameter of the disks is 1000 μm. [Figure 14B] FIG. 14B shows a scanning electron microscope (SEM) image of the direct replica (scale bar: 5 μm). DETAILED DESCRIPTION OF THE INVENTION

[0056] An assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate The present invention relates to an assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate; the at least one circular polycrystalline colloidal monolayer comprises at least one type of uniformly sized particles arranged in juxtaposed monocrystalline domains that are distinct from one another and randomly oriented relative to one another; the diameter of the circular polycrystalline colloidal monolayer is in the range of 0.25 to 2.5 mm. In other words, the assembly according to the present invention comprises at least one circular polycrystalline colloidal monolayer and a solid substrate; the at least one circular polycrystalline colloidal monolayer is immobilized on the solid substrate.

[0057] At least one circular polycrystalline colloidal monolayer The area of ​​at least one circular polycrystalline colloidal monolayer, also referred to as the deposit area, is preferably between 0.049 and 4.9 mm 2 The range is.

[0058] The diameter of the at least one circular polycrystalline colloidal monolayer is preferably in the range of 0.5 to 2 mm, more preferably 1 to 2 mm.

[0059] The at least one circular polycrystalline colloidal monolayer is preferably shaped as a disc or iris (ie, ring).

[0060] According to a preferred embodiment, the assembly of the present invention comprises at least two circular polycrystalline colloid monolayers, which may be different or identical to each other; i.e., the circular polycrystalline colloid monolayers may comprise uniformly sized particles with different or identical cores and / or different or identical average diameters, and / or the diameters of each monolayer may be different or identical. The at least two circular polycrystalline colloid monolayers may be stacked on top of each other or arranged in an array without contacting each other. According to a first variant of this embodiment, the at least two circular polycrystalline colloid monolayers are preferably stacked on top of each other. According to a second variant of this embodiment, the at least two circular polycrystalline colloid monolayers are preferably arranged in an array without contacting each other. According to a third variant of this embodiment, the assembly of the present invention comprises three or more circular polycrystalline colloid monolayers, some of which overlap each other and others of which are arranged in an array without contacting each other.

[0061] Advantageously, the juxtaposed single crystal domains emit a domain-specific structural color when illuminated by a white light source.

[0062] solid substrate Advantageously, the solid substrate corresponds to any solid substrate. Preferably, the contact angle of a droplet of distilled water on the solid substrate is in the range of 20° to 120°, more preferably 40° to 100°.

[0063] The solid substrate is preferably selected from a polymer substrate, a metal substrate or treated or untreated glass.

[0064] According to a preferred embodiment, the solid substrate is a polymer substrate. Examples of suitable polymer substrates according to the present invention include, but are not limited to, polydimethylsiloxane, polyethylene, polypropylene, polystyrene, polyvinyl chloride, rubber, neoprene, nylon, polyacrylonitrile, polycarbonate, polytetrafluoroethylene, and polyvinyl butyral. More preferably, the solid substrate is a polymer substrate selected from polydimethylsiloxane, polyethylene, polypropylene, polystyrene, and polyacrylonitrile. Even more preferably, the solid substrate is polystyrene.

[0065] According to another embodiment, the solid substrate is a metal substrate, preferably selected from aluminum, silver, gold, copper, iron, bronze, steel, chromium, and zinc.

[0066] According to another embodiment, the solid substrate is preferably treated or untreated glass.

[0067] At least one type of uniformly sized particle Advantageously, the at least one type of uniformly sized particles are arranged in 2 to 10,000 juxtaposed single crystal domains.

[0068] The size of each single crystal domain contained in the circular polycrystalline colloid monolayer is preferably 100 to 100,000 μm 2 , more preferably 1000 to 50000 μm 2 The range is.

[0069] Advantageously, the at least one type of uniformly sized particle has a dispersity of less than 5% of the mean diameter, the mean diameter being in the range of 100 nm to 10 μm, preferably 300 nm to 8 μm, more preferably 500 nm to 2.5 μm.

[0070] The core of at least one kind of uniformly sized particle is preferably selected from inorganic material, organic material and their mixture.Preferably, the core of at least one kind of uniformly sized particle is selected from silica, pure polymer or polymer, such as polymer containing additives such as metal oxides, metals and their mixtures;More preferably, the core of at least one kind of uniformly sized particle is made from silica.In other words, at least one kind of uniformly sized particle is preferably silica particle.

[0071] At least one kind of uniform-sized particles is preferably essentially negatively charged or surface-modified to be negatively charged.By "surface-modified", it is understood that according to the present invention, the surface of at least one kind of uniform-sized particles is preferably chemically modified with small organic or inorganic molecules, metals, linear polymers, branched polymers and their mixtures, more preferably with small negatively charged organic or inorganic molecules, negatively charged polymers and their mixtures.Surface-modified uniform-sized particles are commercially available or can be obtained by surface modification methods generally known to those skilled in the art.

[0072] The overall charge of the at least one type of uniformly sized particles is preferably negative, in other words, the at least one type of uniformly sized particles is preferably intrinsically negatively charged or negatively surface-modified.

[0073] Advantageously, the surface of the at least one type of uniformly sized particle essentially has or is functionalized with at least one functional group selected from hydroxyl, carboxylate, sulfate, carbonate and mixtures thereof.

[0074] In a first embodiment, at least one circular polycrystalline colloidal monolayer comprises at least two types of uniformly sized particles having the same average diameter but different cores.

[0075] In a second embodiment, at least one circular polycrystalline colloidal monolayer comprises at least two types of uniformly sized particles having the same core but different average diameters.

[0076] In a third embodiment, the at least one circular polycrystalline colloidal monolayer comprises at least two types of uniformly sized particles having different cores and different average diameters.

[0077] Method for preparing an assembly according to the invention The present invention also relates to a method for preparing an assembly according to the invention as defined above, i.e. an assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate, said method comprising the following steps: a) preparing an aqueous dispersion (A), at least one anionic colloidal particle having an average diameter in the range of 100 nm to 10 μm and a dispersity of less than 5% of the average diameter, - at least one cationic surfactant at a concentration ranging from CMC / 10000 to CMC / 100, wherein the CMC is the critical micelle concentration of the at least one cationic surfactant; and -Aqueous medium preparing an aqueous dispersion (A) containing: b) depositing at least one droplet of the aqueous dispersion (A) prepared in step a) on the upper surface of a solid substrate, wherein the volume of the at least one droplet is 15 μL or less; c) protecting the upper surface of the solid substrate obtained in step b) from airflow and inverting the solid substrate upside down; d) maintaining the solid substrate in an upside-down position to evaporate at least one droplet of aqueous dispersion (A); and then e) optionally, flipping the solid substrate obtained in step d) into the correct orientation; The present invention relates to a method comprising:

[0078] Steps a) to d) and optional step e) of the method for preparing an assembly according to the invention are carried out in this order.

[0079] The process for preparing the assembly according to the present invention is preferably carried out at a temperature in the range of 4 to 99°C, more preferably at ambient temperature.

[0080] The method for preparing the assembly according to the invention can be carried out under various humidity conditions. Advantageously, the method is carried out at a relative humidity in the range of 25-35%.

[0081] In one embodiment, the method for preparing an assembly according to the present invention is carried out at ambient temperature and a relative humidity in the range of 25-35%.

[0082] The method for preparing assemblies according to the present invention is based on the process shown in Figure 1. After flipping a solid substrate upside down, at least one type of dispersed anionic colloidal particles first settles toward the air / water interface of the droplet and adsorbs to this interface thanks to the cationic surfactant (Figure 1A). Then, at least one type of dispersed anionic colloidal particles accumulates as a monolayer toward the center of the droplet (Figure 1B). Meanwhile, the droplet volume gradually decreases by evaporation, leading to gradual crystallization (Figure 1C). When the droplet interface becomes pin-shaped (Figure 1D), final evaporation occurs, leaving a circular deposit on the substrate (Figure 1E).

[0083] The definitions given above for the assembly according to the invention apply mutatis mutandis to the method of preparing the assembly, and vice versa.

[0084] Process a) Aqueous dispersion (A) The aqueous dispersion (A) comprises at least one type of uniformly sized anionic colloidal particles dispersed in an aqueous medium, the particles having a dispersity of less than 5% of the average diameter, and the average diameter being in the range of 100 nm to 10 μm, preferably 300 nm to 8 μm, and more preferably 500 nm to 2.5 μm.

[0085] In one embodiment, the core of at least one dispersed anionic colloidal particle is selected from inorganic material, organic material and their mixture.Preferably, the core of at least one dispersed anionic colloidal particle is selected from silica, pure polymer or polymer containing additives such as metal oxide content, metal and their mixture;More preferably, the core of at least one dispersed anionic colloidal particle is made from silica.In other words, at least one dispersed anionic colloidal particle is preferably silica particle.

[0086] Advantageously, the concentration of the at least one type of dispersed anionic colloidal particles present in the aqueous dispersion (A) ranges from 0.01 to 1 mg / mL, preferably from 0.02 to 0.8 mg / mL, more preferably from 0.04 to 0.6 mg / mL of the aqueous dispersion (A).

[0087] Advantageously, the relative density of each dispersed anionic colloidal particle present in the aqueous dispersion (A) is greater than or equal to 1.05, more advantageously greater than or equal to 1.5, which ensures better settling of the particles.

[0088] Advantageously, the aqueous dispersion (A) comprises at least two types of dispersed anionic colloidal particles that are different from one another. By "different particles" is meant, according to the invention, that the at least two types of dispersed anionic colloidal particles have different cores and / or different average diameters.

[0089] In a first embodiment, the aqueous dispersion (A) comprises at least two types of dispersed anionic colloidal particles having the same average diameter but different cores.

[0090] In a second embodiment, the aqueous dispersion (A) contains at least two types of dispersed anionic colloidal particles with the same core but different average diameters. This allows for the formation of a circular polycrystalline colloidal monolayer in which the particles are separated by size. Indeed, due to their greater weight, the majority of the larger particles gather at the center of the particle patch on the fluid interface and eventually crystallize there; meanwhile, the smaller particles accumulate and crystallize in the outer regions of the patch, with only a few particles remaining trapped in the gaps formed by the crystallization of the larger particles (Figure 2).

[0091] In a third embodiment, the aqueous dispersion (A) comprises at least two types of dispersed anionic colloidal particles having different cores and different average diameters.

[0092] The aqueous dispersion (A) prepared in step a) of the method according to the invention further comprises at least one cationic surfactant in a concentration ranging from CMC / 10000 to CMC / 100, CMC being the critical micelle concentration of the at least one cationic surfactant.

[0093] The concentration of the at least one cationic surfactant is preferably in the range of CMC / 8000 to CMC / 500, more preferably in the range of CMC / 5000 to CMC / 1000. All known methods for determining the CMC of cationic surfactants can be used to determine the CMC of the at least one cationic surfactant present in the aqueous dispersion (A). In particular, procedures based on measurements at different surfactant concentrations or surface tension measurements are among the methods well known to those skilled in the art. The CMC values ​​of most known surfactants are also published and available in textbooks, databases, or scientific papers.

[0094] Advantageously, the at least one cationic surfactant present in the aqueous dispersion (A) is optionally selected from polyoxyalkylenated primary, secondary, or tertiary fatty amine salts, quaternary ammonium salts, nitrogen-containing heterocyclic surfactants (e.g., imidazolium salts, pyrrolidinium salts, and pyridinium salts), and mixtures thereof, preferably from quaternary ammonium salts such as dodecyltrimethylammonium halides, and more preferably from dodecyltrimethylammonium bromide. The CMC value of dodecyltrimethylammonium bromide in water at ambient temperature and atmospheric pressure is 0.0155 to 0.016 mol / L.

[0095] Step b) Droplets of aqueous dispersion (A) The method for preparing an assembly according to the present invention further comprises a step b), in which at least one droplet of the aqueous dispersion (A) prepared in step a) is deposited on top of a solid substrate.

[0096] Advantageously, the drop volume, which corresponds to the volume of the drops of aqueous dispersion (A) deposited in step b), ranges from 0.25 μL to 15 μL, preferably from 4 μL to 10 μL.

[0097] The contact angle of droplets of the aqueous dispersion (A) prepared in step a) on the solid substrate is preferably in the range of 20° to 120°, more preferably 40° to 100°.

[0098] From step c) to any step e) The method for preparing an assembly according to the present invention further comprises step c), in which the top surface of the solid substrate obtained in step b) is protected from airflow and the solid substrate is turned upside down.

[0099] Step c) is preferably carried out immediately after depositing the droplets of aqueous dispersion (A) on top of the solid substrate (ie immediately after step b)), without any intermediate waiting time.

[0100] The method for preparing an assembly according to the present invention further comprises step d), in which the inverted solid substrate of step c) is maintained in an upside-down position to allow the droplets of aqueous dispersion (A) to evaporate. In other words, during step d), the aqueous medium of the droplets of aqueous dispersion (A) evaporates while at least one type of dispersed anionic colloidal particles accumulates and crystallizes, leaving behind a circular deposit on the solid substrate, as shown in FIG.

[0101] The method for preparing an assembly according to the present invention may further comprise an optional step e) in which the solid substrate maintained in an upside-down position in step d) is inverted to the correct orientation to allow the droplets of aqueous dispersion (A) to evaporate.

[0102] According to a first embodiment, step d) is optionally carried out until the droplets of aqueous dispersion (A) have completely evaporated, before carrying out step e). In other words, according to this embodiment, the inverted solid substrate is maintained in an upside-down position until the aqueous medium of the droplets of aqueous dispersion (A) has completely evaporated, before optionally inverting the solid substrate in the correct orientation according to step e) of the method of the present invention. This allows obtaining, at the end of step d), a polycrystalline colloidal monolayer in the form of a disk.

[0103] According to the second embodiment, step d) is stopped before the droplets of aqueous dispersion (A) completely evaporate, and step e) is necessarily performed after step d). In other words, according to this embodiment, step e) is necessarily performed before the complete evaporation of the aqueous medium of the droplets of aqueous dispersion (A). This allows obtaining a polycrystalline colloidal monolayer having an iris (i.e., ring) shape at the end of step e). Indeed, during the evaporation of the droplets of aqueous dispersion (A), at least one type of dispersed anionic colloidal particles accumulates and adsorbs to the air / water interface (Figure 3A). Then, after inverting the solid substrate obtained in step d) before the complete evaporation of the droplets of aqueous dispersion, the at least one type of dispersed anionic colloidal particles still trapped at the air / water interface accumulates at the edge of the droplet and gradually distributes along the entire diameter (Figure 3B), thereby resulting in the formation of a polycrystalline colloidal monolayer having a ring shape.

[0104] Thus, depending on whether step d) is carried out until complete evaporation of the droplets of aqueous dispersion (A) or is stopped before complete evaporation and followed by optional step e), a circular polycrystalline colloidal monolayer is obtained either at the end of step d) or at the end of optional step e).

[0105] The time for holding the solid substrate upside down is preferably in the range of 10 to 240 minutes to ensure complete evaporation of the aqueous medium from the droplets of aqueous dispersion (A), although the exact time depends on the droplet volume, temperature, and humidity conditions. Alternatively, to obtain a polycrystalline colloidal monolayer having an iris (i.e., ring) shape, the time for holding the solid substrate upside down is preferably in the range of 10 to 120 minutes, and step e) is necessarily performed before complete evaporation of the droplets of aqueous dispersion (A).

[0106] Further steps Further step c') The method for preparing an assembly according to the invention may further comprise a further step carried out between steps c) and d), consisting of injecting a further volume of aqueous dispersion (A) into the drop of aqueous dispersion (A) inverted in step c).

[0107] This further step is further referred to as step c'). This further step c') makes it possible to increase the volume of the droplets of aqueous dispersion (A) that adhere to the inverted solid substrate and therefore to increase the final deposition area. In other words, when step c') is carried out in the method according to the invention, the diameter of the polycrystalline colloidal monolayer thus obtained on the solid substrate is larger.

[0108] Advantageously, the total volume of the droplets of aqueous dispersion (A) in step c'), corresponding to the sum of the volume of the droplets of aqueous dispersion (A) deposited in step b) and the volume of the further aqueous dispersion (A) injected in step c'), is not more than 55 μL. In other words, the further volume of aqueous dispersion (A) injected in step c') is preferably not more than 40 μL, more preferably in the range of 0.25 μL to 40 μL, more preferably 10 μL to 30 μL.

[0109] Repeat from step b) to any step e). According to one embodiment, the method for preparing an assembly according to the present invention may further comprise repeating steps b) through e) after optional step e), in which a second droplet of aqueous dispersion (A) prepared in step a) is deposited either on top of (i.e., on top of) or adjacent to (without contact with) the circular polycrystalline colloidal monolayer obtained in step d) or optional step e); the volume of the second droplet of aqueous dispersion (A) is 15 μL or less. The contact angle of the second droplet of aqueous dispersion (A) on the solid substrate is preferably in the range of 20° to 120°, more preferably 40° to 100°. Preferably, the second droplet of aqueous dispersion (A) prepared in step a) is deposited on the circular polycrystalline colloidal monolayer obtained in step d) or optional step e).

[0110] In other words, after depositing a second droplet of aqueous dispersion (A) on top of the circular polycrystalline colloidal monolayer obtained in step d) or optional step e), the solid substrate thus obtained is protected from airflow and inverted upside down (repeated step c)), and then maintained in the inverted position to allow the second droplet of aqueous dispersion (A) to evaporate (repeated step d)); and then optionally inverted back upright (repeated step e) to obtain another circular polycrystalline colloidal monolayer superimposed on the circular polycrystalline colloidal monolayer obtained in step d) or optional step e), or aligned in an array with but not in contact with the circular polycrystalline colloidal monolayer obtained in step d) or optional step e). Crystallization of the new monolayer at the liquid interface allows the domain orientation and interparticle distance of each monolayer to remain unchanged between successive depositions.

[0111] Advantageously, the volume of the second droplet of aqueous dispersion (A) deposited in the repetition of step b) ranges from 0.25 μL to 15 μL, more advantageously from 4 μL to 10 μL.

[0112] Further steps f) to j) According to another embodiment, the method for preparing an assembly according to the invention comprises the following steps: f) preparing an aqueous dispersion (B) different from the aqueous dispersion (A), at least one anionic colloidal particle having an average diameter in the range of 100 nm to 10 μm and a dispersity of less than 5% of the diameter, - at least one cationic surfactant at a concentration ranging from CMC / 10000 to CMC / 100, wherein the CMC is the critical micelle concentration of the at least one cationic surfactant; and -Aqueous medium preparing an aqueous dispersion (B) containing: g) depositing at least one droplet of the aqueous dispersion (B) prepared in step f) either on (i.e., on top of) or adjacent to, but not in contact with, the circular polycrystalline colloidal monolayer obtained in step d) or optional step e) (FIG. 4A), wherein the volume of the droplet is 15 μL or less and the contact angle of the droplet on the solid substrate is preferably in the range of 20° to 120°; h) protecting the top surface of the solid substrate obtained in step g) from airflow and flipping the solid substrate upside down (Figure 4B); i) maintaining the solid substrate in an upside-down position to evaporate at least one droplet of aqueous dispersion (B); and then j) optionally, flipping the solid substrate obtained in step i) into the correct orientation; It may further include: This embodiment makes it possible to obtain another circular polycrystalline colloidal monolayer superimposed on or adjacent in an array (but without contact) to the circular polycrystalline colloidal monolayer previously obtained in step d) or optional step e). The crystallization of the new monolayer at the liquid interface allows the domain orientation and interparticle distance of each monolayer to remain unchanged between successive depositions. Preferably, at least one droplet of the aqueous dispersion (B) prepared in step f) is deposited onto the circular polycrystalline colloidal monolayer previously obtained in step d) or optional step e).

[0113] The further steps f) to j) of the method for preparing an assembly according to the invention are carried out in this order.

[0114] The at least one cationic surfactant, the at least one type of dispersed anionic colloidal particles, and the aqueous medium suitable for the aqueous dispersion (A) described above are also suitable in nature and content for the aqueous dispersion (B) prepared in optional step f).

[0115] When the method for preparing an assembly according to the present invention comprises steps f) to optional step j), step h) is preferably carried out immediately after the deposition of the droplets of aqueous dispersion (B) (i.e., immediately after step g) without any intermediate waiting time.

[0116] According to a first embodiment, when the method for preparing an assembly according to the present invention comprises steps f) through j), step i) is carried out until the droplets of aqueous dispersion (B) have completely evaporated (optionally before step j) is carried out (FIG. 4C). In other words, according to this embodiment, the solid substrate inverted in step i) is maintained in an upside-down position until the aqueous medium of the droplets of aqueous dispersion (B) has completely evaporated, before optionally inverting the solid substrate in step j). This allows obtaining another polycrystalline colloidal monolayer, preferably superimposed on the circular polycrystalline colloidal monolayer previously obtained in step d) or optional step e), and the monolayer deposited by steps f) through i) is a disk.

[0117] According to a second embodiment, when the method for preparing an assembly according to the present invention includes steps f) to j), step i) is stopped before the droplets of aqueous dispersion (B) have completely evaporated. In other words, according to this embodiment, step j) is necessarily performed before the aqueous medium of the droplets of aqueous dispersion (B) has completely evaporated. This makes it possible to obtain another polycrystalline colloidal monolayer, preferably superimposed on the circular polycrystalline colloidal monolayer previously obtained in step d) or any step e), and the monolayer deposited by steps f) to j) has an iris (i.e., ring) shape.

[0118] In one embodiment, when the method for preparing an assembly according to the present invention comprises steps f) through optional step j), the average diameter of the at least one type of dispersed anionic colloidal particles of aqueous dispersion (B) is less than or equal to the average diameter of the at least one type of dispersed anionic colloidal particles of aqueous dispersion (A).

[0119] In one embodiment, when the method for preparing an assembly according to the present invention comprises steps f) through optional step j), the method further comprises at least one repetition of steps f) through optional step j), thereby obtaining at least one additional circular polycrystalline colloidal monolayer, preferably superimposed on the original circular polycrystalline colloidal monolayer obtained by steps f) through optional step j).

[0120] In one embodiment, when the method for preparing an assembly according to the present invention comprises steps f) through optional step j), steps d) and i) are carried out until the aqueous medium of the droplets of aqueous dispersion deposited in steps b) and g) respectively has completely evaporated, thereby obtaining another polycrystalline colloidal monolayer preferably superimposed on the circular polycrystalline colloidal monolayer obtained in step d), and both deposited polycrystalline colloidal monolayers being disks.

[0121] Protection of at least one circular polycrystalline colloidal monolayer The method according to the invention may optionally further comprise a step of protecting the at least one circular polycrystalline colloidal monolayer, this further step allowing for better protection of the at least one monolayer against external attack.

[0122] Any method known to those skilled in the art for the protection of solid substrates can be applied to the protection of at least one circular polycrystalline colloidal monolayer.

[0123] One example of protecting the at least one circular polycrystalline colloidal monolayer is injecting a liquid heat-curable or UV-curable prepolymer onto the at least one circular polycrystalline colloidal monolayer and then curing the liquid prepolymer.

[0124] Transfer of at least one circular polycrystalline colloidal monolayer The method according to the invention may optionally further comprise a step of transferring at least one circular polycrystalline colloidal monolayer obtained in step d) or any step e), i) or j) preferably onto a polymer film.

[0125] Any method known to those skilled in the art for transferring nano / micro structures to polymeric materials can be applied to the present invention.

[0126] The transfer of at least one circular polycrystalline colloidal monolayer can advantageously be carried out in a hardened polymer slab. By way of example, the transfer of at least one circular polycrystalline colloidal monolayer obtained in step d) or any of steps e), i) or j) can be carried out by the following steps: k) pouring a liquid heat-curable or UV-curable prepolymer onto the at least one circular polycrystalline colloidal monolayer obtained in step d) or any step e), i) or j) and onto the substrate on which the monolayer is immobilized; l) curing the liquid prepolymer of step k); and then m) Peeling off the hardened polymer slab may be carried out in accordance with The at least one circular polycrystalline colloidal monolayer of step k) is embedded in the hardened polymer slab of step m).

[0127] In step k) of transferring in the hardened polymer slab the at least one circular polycrystalline colloidal monolayer obtained in step d) or any of steps e), i) or j), the at least one circular polycrystalline colloidal monolayer remains strongly attached to the underlying substrate and is not damaged by the liquid prepolymer solution, thereby allowing it to be transferred undamaged and while maintaining the unique arrangement of crystalline domains with specific orientations.

[0128] Advantageously, the liquid thermosetting prepolymer that can be used to transfer at least one circular polycrystalline colloidal monolayer is selected from silicones such as fluorosilicones, polyurethanes, bakelite, duroplasts, melamines, epoxies, benzoxazines, polyimides, bismaleimides, cyanate esters, furans, thiolites, and vinyl esters. In a preferred embodiment, the liquid thermosetting prepolymer is a silicone prepolymer, more preferably polydimethylsiloxane.

[0129] Advantageously, the UV-curable prepolymer that can be used to transfer at least one circular polycrystalline colloid monolayer is selected from acrylated polyurethanes, epoxies, thiolenes, acrylated epoxies, acrylated polyesters, acrylate silicones, and fluorosilicones. In a preferred embodiment, the UV-curable prepolymer is a thiolenes prepolymer. An example of a commercially available UV-curable thiolenes prepolymer is Norland Optical Adhesives (NOA 81) sold by Norland Products.

[0130] The transfer of at least one circular polycrystalline colloidal monolayer in a cured polymer slab can also be performed by replica molding using either a direct replica or an inverse replica. As an example, the molding of at least one circular polycrystalline colloidal monolayer obtained in step d) or any of steps e), i) or j) in a cured polymer slab can be performed by the following steps: n) subjecting at least one circular polycrystalline colloidal monolayer obtained in step d) or any step e), i) or j) and the substrate on which the monolayer is immobilized to a surface functionalization treatment; o) pouring a liquid thermosetting prepolymer onto the treated surface of step n); p) curing the liquid thermosetting prepolymer of step o) to obtain a cured polymer slab; and then q) peeling off the hardened polymer slab of step p) to obtain in the peeled hardened polymer slab a mold of at least one circular polycrystalline colloidal monolayer obtained in step d) or any step e), i) or j) of the method according to the invention (see Figure 6C for steps m) and n)). may include:

[0131] According to a preferred embodiment, the surface functionalization treatment in step n) is a chemical passivation of the surface, such as silanization with 1H,1H,2H,2H-perfluorooctyltrichlorosilane, which renders the at least one circular polycrystalline colloidal monolayer obtained in step d) or any of steps e), i), or j) non-adhesive to the liquid thermosetting prepolymer in step o). Therefore, the at least one circular polycrystalline colloidal monolayer obtained in step d) or any of steps e), i), or j) does not adhere to the liquid thermosetting prepolymer surface, resulting in the colloidal particles remaining on the substrate in step n) and forming a structural mold in the peeled-off cured polymer slab in step q).

[0132] The direct replication of at least one circular polycrystalline colloidal monolayer obtained in step d) or any of steps e), i) or j) can be carried out by the following steps: r) pouring a liquid thermosetting or UV curable prepolymer onto the mold obtained in the molding of at least one circular polycrystalline colloidal monolayer obtained in step d) or optional steps e), i) or j) in a cured polymer slab; s) curing the liquid prepolymer of step r) to obtain a cured polymer slab; and then t) peeling off the hardened polymer slab of step s) to obtain in the hardened polymer slab a replica of at least one circular polycrystalline colloidal monolayer obtained in step d) or any step e), i) or j) of the method according to the invention. may include:

[0133] Direct or inverse replication of the at least one circular polycrystalline colloidal monolayer can be performed in different cured polymer slabs using the same type of at least one circular polycrystalline colloidal monolayer. In other words, starting from a unique type of at least one circular polycrystalline colloidal monolayer, a first replication of the at least one circular polycrystalline colloidal monolayer can be performed in a first cured polymer slab, followed by a second replication in a second cured polymer slab, etc.

[0134] The aforementioned liquid thermosetting and / or UV curable prepolymers are also inherently suitable for replica molding of at least one circular polycrystalline colloidal monolayer in a cured polymer slab.

[0135] Assemblies directly obtained by the method according to the invention The present invention further relates to an assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate, directly obtainable by the method according to the invention.

[0136] Use of assemblies containing at least one circular polycrystalline colloidal monolayer The present invention also relates to the use of the assembly according to the present invention for labeling products of interest by direct deposition or, preferably, transfer onto a polymer film. The unique arrangement of crystalline domains with specific orientations in the monolayer allows for rapid identification of products of interest. Furthermore, the structural color resulting from white light reflected by the crystalline domains can enable such identification. Due to their complex and unique patterns, the assembly according to the present invention can be used, for example, for anti-counterfeiting or product identification. [Example]

[0137] The present invention is further illustrated by the following examples.

[0138] Example 1: Application of the method according to the invention to prepare an assembly comprising one polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene.

[0139] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Silica particles (average diameter = 0.56 μm, dispersity 3.6%, concentration = 0.05 mg / mL) preparing an aqueous dispersion containing: b) depositing a droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 5 μL); c) closing the Petri dish of step b) and inverting it upside down; and then d) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated in about 100 minutes. at ambient temperature and 40% relative humidity.

[0140] result An assembly is obtained containing one polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene. The disk has a diameter of 0.75 mm and a deposition area corresponding to the disk area of ​​0.44 mm. 2 Reflectance microscope and SEM images of polycrystalline colloidal monolayer disks of silica particles are shown in Figures 5A and 5B. The structural color arises from domains of tightly packed particles, which can be observed in Figure 5B, where the particles are packed with various orientations relative to the light source.

[0141] Example 2: Application of the method according to the invention to prepare four assemblies each containing one polycrystalline colloidal monolayer disk of particles immobilized on a solid substrate.

[0142] material and method The same procedure as presented in Example 1 was applied, except that three different sets of conditions were used: [Table 1]

[0143] In set 1, the surface of the polystyrene particles is functionalized with sulfate and high density carboxylate.

[0144] result Four different assemblies were obtained, each containing one polycrystalline colloidal monolayer disk of particles immobilized on the substrate. For the first set of conditions, a reflected light microscope image of the corresponding polycrystalline colloidal monolayer disk of polystyrene particles (surface-modified with sulfate and carboxylate) immobilized on a polystyrene substrate is shown in Figure 6A (disk diameter: 600 μm). Similarly, for the second and third sets of conditions, reflected light microscope images of the corresponding polycrystalline colloidal monolayer disk of silica particles immobilized on a polystyrene substrate are shown in Figure 6B and Figure 6C (disk diameters: 1000 μm and 500 μm, respectively). For the fourth set of conditions, a reflected light microscope image of the corresponding polycrystalline colloidal monolayer disk of silica particles immobilized on an untreated glass substrate is shown in Figure 6D (disk diameter: 1000 μm).

[0145] Comparative Example 1: Application of the method according to the invention without cationic surfactant. material and method Comparative Example 1 differs from Example 1 in that the aqueous dispersion in step a) does not contain dodecyltrimethylammonium bromide, in other words, the aqueous dispersion in step a) in Comparative Example 1 does not contain a cationic surfactant.

[0146] result Unlike Example 1, which yields an assembly containing a single polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene, Comparative Example 1 yields a thick multilayer deposit with a smaller diameter (200 μm). This result demonstrates the need to have at least one cationic surfactant in the aqueous dispersion for the method according to the invention.

[0147] Comparative Example 2: Application of the method according to the invention without the step of flipping the solid substrate upside down. material and method Comparative Example 2 differs from Example 1 in that steps c) to d) are replaced by step b) of closing the Petri dish, i.e., the solid substrate of Comparative Example 2 is not flipped upside down.

[0148] result Unlike Example 1, which yields an assembly containing a single polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene, Comparative Example 2 yields non-circular multilayer deposits (typical size 700 μm) with only localized micrometric domains exhibiting structural color, with the domains exhibiting a lack of overall organization and clear domain boundaries. This result demonstrates the necessity of flipping the solid substrate upside down in the method according to the present invention.

[0149] Comparative Example 3: Application of the method according to the invention using a cationic surfactant at a concentration equal to CMC / 16. material and method Comparative Example 3 differs from Example 1 in that the cationic surfactant dodecyltrimethylammonium bromide has a concentration equal to 1 mM, which corresponds to a CMC / 16.

[0150] result Unlike Example 1, which yields an assembly containing a single polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene, Comparative Example 3 yields an irregular deposit 800 mm in diameter with localized gel-like structures and particles spread throughout the wetted area. This result demonstrates the need for a cationic surfactant concentration in the range of CMC / 10,000 to CMC / 100 for the method according to the invention.

[0151] Example 3: Application of the method according to the invention to prepare an assembly having the shape of an iris (i.e., a ring) and comprising one polycrystalline colloidal monolayer of silica particles immobilized on polystyrene.

[0152] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Silica particles (average diameter = 0.56 μm, dispersity 3.6%, concentration = 0.05 mg / mL) preparing an aqueous dispersion containing: b) depositing a droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 5 μL); c) closing the Petri dish of step b) and inverting it upside down; d) maintaining the solid substrate in an upside-down position for about 90-105 minutes; e) inverting the Petri dish obtained in step d) into the correct orientation before the deionized water has completely evaporated; and then f) maintaining the solid substrate in an upright position until the deionized water has completely evaporated; at ambient temperature and 40% relative humidity.

[0153] result The resulting assembly has an iris shape and consists of a polycrystalline colloidal monolayer of silica particles immobilized on polystyrene. The disk has a diameter of 850 μm, with a central hole of 350 μm. A reflection microscope image of the polycrystalline colloidal monolayer of silica particles is shown in Figure 7.

[0154] Example 4: Application of the method according to the invention to prepare an assembly comprising one polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene.

[0155] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (5 μM, corresponding to a concentration of CMC / 3200), deionized water, and -Silica particles (average diameter = 2.4 μm, dispersity 1.7%, concentration = 0.05 mg / mL) preparing an aqueous dispersion containing: b) depositing droplets of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish; c) closing the Petri dish of step b) and inverting it upside down; d) injecting a further volume of aqueous dispersion into the inverted droplets of aqueous dispersion from step c); and then e) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated, which takes approximately 2-4 hours. at ambient temperature and 40% relative humidity.

[0156] Two different sets of conditions were applied: [Table 2]

[0157] result Two different assemblies were obtained, each containing one polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene. Reflectance microscope images of polycrystalline colloidal monolayer disks of silica particles corresponding to the first and second set of conditions are shown in Figures 8A and 8B, respectively. For the first set of conditions, the 3.5 mm 2 A deposition area of ​​0.125 mm (diameter 2100 μm) was obtained in the second set of conditions. 2 A deposition area of ​​400 μm in diameter is obtained. Thus, by injecting additional volumes of aqueous dispersion, larger polycrystalline colloidal monolayer disks can be obtained without exceeding the 15 μl volume in step b) required for the droplet of aqueous dispersion to remain retained on the substrate when flipped upside down.

[0158] Example 5: Application of the method according to the invention using dispersed anionic colloidal particles with two different mean diameters.

[0159] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Two types of silica particles (average diameter = 0.56 μm, dispersity 3.6% at a concentration of 0.05 mg / mL, and average diameter = 2.4 μm, dispersity 1.7% at a concentration of 0.1 mg / mL) preparing an aqueous dispersion containing: b) depositing a droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 5 μL); c) closing the Petri dish of step b) and inverting it upside down; and then d) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated in about 100 minutes. at ambient temperature and 40% relative humidity.

[0160] result An assembly containing a single polycrystalline colloidal monolayer disk of silica particles immobilized on polystyrene was obtained, with large (average diameter = 2.4 μm, dispersity 1.7%) and small (average diameter = 0.56 μm, dispersity 3.6%) particles separated by size. The disk diameter is 825 μm. A reflected light microscope image of the polycrystalline colloidal monolayer disk of silica particles is shown in Figure 9. Thus, the method according to the present invention makes it possible to achieve controlled colloidal deposition with complex structures that are not easily accessible by common deposition strategies.

[0161] Example 6: Application of the method according to the invention to prepare an assembly comprising two polycrystalline colloidal monolayer disks of silica particles superimposed on each other and immobilized on polystyrene.

[0162] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Silica particles (average diameter = 0.56 μm, dispersity 3.6%, concentration = 0.05 mg / mL) preparing an aqueous dispersion containing: b) depositing a first droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 5 μL); c) closing the Petri dish of step b) and inverting it upside down; d) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated in about 100 minutes; e) inverting the Petri dish obtained in step d) into the correct orientation; f) depositing a second droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 5 μL); g) closing the Petri dish of step f) and inverting it upside down; and then h) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated in about 100 minutes. at ambient temperature and 40% relative humidity.

[0163] result An assembly was obtained containing two polycrystalline colloidal monolayer disks of silica particles immobilized on polystyrene, with the two monolayers stacked on top of each other. The disks had a diameter of 750 μm. A reflected light microscope image of the two polycrystalline colloidal monolayer disks of silica particles is shown in Figure 10.

[0164] Example 7: Application of the method according to the invention to prepare an assembly comprising two polycrystalline colloidal monolayer disks of silica particles superimposed on each other and immobilized on polystyrene.

[0165] material and method The method according to the invention comprises the following steps: a) preparing a first aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Silica particles (average diameter = 0.98 μm, dispersity 2.7%, concentration = 0.1 mg / mL) preparing a first aqueous dispersion containing: b) depositing a droplet of the first aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 7 μL); c) closing the Petri dish of step b) and inverting it upside down; d) maintaining the solid substrate in an upside down position until the deionized water has completely evaporated in about 120 minutes; e) turning the Petri dish obtained in step d) upside down and opening it; f) preparing a second aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Silica particles (average diameter = 0.56 μm, dispersity 3.6%, concentration = 0.05 mg / mL) preparing a second aqueous dispersion containing: g) depositing a droplet of the second aqueous dispersion prepared in step f) on the upper surface of the polycrystalline colloidal monolayer disk of silica particles obtained in step d) (droplet volume = 10 μL); h) closing the Petri dish of step b) and inverting it upside down; and then i) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated; at ambient temperature and 40% relative humidity.

[0166] result An assembly was obtained containing two polycrystalline colloidal monolayer disks of silica particles immobilized on polystyrene, with the two monolayers stacked on top of each other. The first disk, obtained by steps a) through d), had a diameter of 1000 μm, while the second disk, obtained by steps f) through i), stacked on top of the first, had a diameter of 800 μm. Reflection microscope images of the two polycrystalline colloidal monolayer disks of silica particles are shown in Figure 11. Examples 6 and 7 demonstrate the fact that the method for preparing assemblies according to the present invention allows for the formation of ordered monolayers on top of already formed monolayers, advantageously producing colloidal materials with hierarchical structures.

[0167] Example 8: Application of the method according to the invention with the further step of transfer of a circular polycrystalline colloidal monolayer in a hardened polymer slab.

[0168] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -Silica particles (average diameter = 0.56 μm, dispersity 3.6%, concentration = 0.05 mg / mL) preparing an aqueous dispersion containing: b) depositing a droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 15 μL); c) closing the Petri dish of step b) and inverting it upside down; d) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated; and then e) turning the Petri dish obtained in step d) over in the correct orientation at ambient temperature and 40% relative humidity.

[0169] The polycrystalline colloidal monolayer disks of silica particles thus obtained were subjected to the following steps: a) pouring UV-curable NOA 81 photopolymer onto the polycrystalline colloidal monolayer disk of silica particles obtained in step d) and onto the polystyrene on which the monolayer is immobilized; b) applying a flat PDMS-based polymer slab on top of the NOA 81 photopolymer of step a); c) curing the NOA 81 photopolymer of step b) by UV irradiation; d) removing the flat PDMS-based polymer slab from on top of the cured NOA-based polymer slab of step c); and then e) Peeling off the hardened polymer slab to a hardened polymer slab.

[0170] result An assembly containing a single polycrystalline colloidal monolayer disk of silica particles embedded in a NOA-based polymer slab was obtained. The disk had a diameter of 1250 μm. Reflectance microscope and SEM images of the polycrystalline colloidal monolayer disk embedded in a NOA-based polymer slab are shown in Figures 12A and 12B.

[0171] Example 9: Application of the method according to the invention with the further step of transfer of a circular polycrystalline colloidal monolayer in a hardened polymer slab.

[0172] material and method The method according to the invention comprises the following steps: a) preparing an aqueous dispersion, - dodecyltrimethylammonium bromide (10 μM, corresponding to a concentration of CMC / 1600), deionized water, and -silica particles (average diameter = 0.56 μm, dispersity 3.6%, concentration = 0.05 mg / mL); preparing an aqueous dispersion containing: b) depositing a droplet of the aqueous dispersion prepared in step a) onto the top surface of a polystyrene (PS) Petri dish (droplet volume = 15 μL); c) closing the Petri dish of step b) and inverting it upside down; d) maintaining the solid substrate in an upside-down position until the deionized water has completely evaporated; and then e) turning the Petri dish obtained in step d) over in the correct orientation at ambient temperature and 40% relative humidity.

[0173] The polycrystalline colloidal monolayer disks of silica particles thus obtained were subjected to the following steps: a) subjecting the polycrystalline colloidal monolayer disks of silica particles obtained in step d) and the polystyrene on which the monolayer is immobilized to silanization with 1H,1H,2H,2H-perfluorooctyltrichlorosilane; b) pouring liquid PDMS onto the treated surface of step a); c) curing the liquid PDMS of step b) at temperature to obtain a cured PDMS-based polymer slab; d) Peeling off the cured PDMS-based polymer slab of step c). is used to mold into a thermoset polymer slab. The mold thus obtained is used to carry out the following steps: a) pouring UV-curable NOA photopolymer onto the exfoliated cured PDMS-based polymer slab obtained in step d) of molding polycrystalline colloidal monolayer disks of silica particles; b) curing the NOA photopolymer of step a) with UV radiation to obtain a UV-cured NOA-based polymer slab; and then c) peeling off the cured NOA-based polymer slab of step b). is used to replicate polycrystalline colloidal monolayer disks of silica particles in UV-cured polymer slabs.

[0174] result In step d), polycrystalline colloidal monolayer disks of silica particles with a diameter of 1000 μm are obtained. A mold of the polycrystalline colloidal monolayer disk is then obtained in a cured PDMS-based polymer slab. The diameter of the mold is also 1000 μm. Reflected light microscope and SEM images of the mold are shown in Figures 13A and 13B. A direct replica of the polycrystalline colloidal monolayer disk of silica particles obtained in step d) of the method according to the invention is then obtained in a cured NOA-based polymer slab. The diameter of the direct replica is also 1000 μm. Reflected light microscope and SEM images of the direct replica are shown in Figures 14A and 14B.

[0175] Examples 8 and 9 demonstrate that the method of the present invention not only provides assemblies containing at least one circular polycrystalline colloidal monolayer, but also accurately transfers the circular polycrystalline colloidal monolayer without damaging it. The domain structure and orientation of the original circular polycrystalline colloidal monolayer are transferred identically, thus retaining the same structural color that is easily detectable under a white light source. The resulting polymer slabs can then be used to label products, enabling their identification.

Claims

1. 1. An assembly comprising at least one circular polycrystalline colloidal monolayer immobilized on a solid substrate, said at least one circular polycrystalline colloidal monolayer comprising at least one type of uniformly sized particles arranged in juxtaposed single-crystalline domains that are different from one another and randomly oriented relative to one another, and wherein the diameter of said circular polycrystalline colloidal monolayer is in the range of 0.25 to 2.5 mm.

2. 2. The assembly of claim 1, wherein the diameter of said at least one circular polycrystalline colloidal monolayer is in the range of 0.5 to 2 mm, preferably 1 to 2 mm.

3. The size of each single crystal domain is 100 to 100,000 μm ２ 3. The assembly of claim 1 or claim 2, wherein the range is:

4. 4. The assembly according to any one of claims 1 to 3, wherein the core of said at least one type of uniformly sized particle is selected from inorganic materials, organic materials and mixtures thereof, preferably from silica, polymers such as pure polymers or polymers containing additives such as metal oxide inclusions, metals and mixtures thereof.

5. 5. The assembly according to any one of claims 1 to 4, wherein the at least one type of uniformly sized particle is intrinsically negatively charged or is surface-modified, preferably with small organic or inorganic molecules, metals, linear polymers, branched polymers and mixtures thereof, more preferably with small negatively charged organic or inorganic molecules, negatively charged polymers and mixtures thereof.

6. 6. The assembly according to any one of claims 1 to 5, comprising at least two circular polycrystalline colloid monolayers, which are different from each other or identical to each other, and the at least two circular polycrystalline colloid monolayers are arranged in an array, overlapping each other or not in contact with each other.

7. The following steps: a) preparing an aqueous dispersion (A), - at least one anionic colloidal particle having an average diameter ranging from 100 nm to 10 μm and a dispersity of less than 5% of said diameter; - at least one cationic surfactant at a concentration ranging from CMC / 10000 to CMC / 100, wherein CMC is the critical micelle concentration of said at least one cationic surfactant, and -Aqueous medium preparing an aqueous dispersion (A) containing: b) depositing at least one droplet of the aqueous dispersion (A) prepared in step a) on the upper surface of a solid substrate, wherein the volume of the at least one droplet is 15 μL or less; c) protecting the upper surface of the solid substrate obtained in step b) from airflow and turning the solid substrate upside down; d) maintaining the solid substrate in the upside-down position to evaporate the at least one droplet of the aqueous dispersion (A); and then e) optionally, flipping the solid substrate obtained in step d) into the correct orientation; A method for preparing an assembly according to any one of claims 1 to 6, comprising:

8. 8. The method according to claim 7, wherein the contact angle of a droplet of the aqueous dispersion (A) prepared in step a) on the solid substrate is in the range of 20° to 120°, preferably 40° to 100°.

9. 9. The method of claim 7 or claim 8, wherein the concentration of the at least one type of dispersed anionic colloidal particle is in the range of 0.01 to 1 mg / mL, preferably 0.02 to 0.8 mg / mL, more preferably 0.04 to 0.6 mg / mL of the aqueous dispersion (A).

10. 10. The method according to any one of claims 7 to 9, wherein the concentration of the cationic surfactant ranges from CMC / 8000 to CMC / 500, preferably from CMC / 5000 to CMC / 1000.

11. The method according to any one of claims 7 to 10, further comprising the step between step c) and step d) of injecting a further volume of the aqueous dispersion (A) into the droplet of the aqueous dispersion (A) inverted in step c).

12. 12. The method of any one of claims 7 to 11, further comprising repeating steps b) to d) or optionally to step e) after step d) or optional step e), wherein a second droplet of the aqueous dispersion (A) prepared in step a) is deposited either on top of or adjacent to, but not in contact with, the circular polycrystalline colloidal monolayer obtained in step d) or optional step e), and wherein the volume of the second droplet of aqueous dispersion (A) is 15 μL or less.

13. The following steps: f) preparing an aqueous dispersion (B) different from the aqueous dispersion (A), - at least one anionic colloidal particle having an average diameter ranging from 100 nm to 10 μm and a dispersity of less than 5% of said diameter; - at least one cationic surfactant at a concentration ranging from CMC / 10000 to CMC / 100, wherein CMC is the critical micelle concentration of said at least one cationic surfactant, and -Aqueous medium preparing an aqueous dispersion (B) containing: g) depositing at least one droplet of said aqueous dispersion (B) prepared in step f) either on or adjacent to, but not in contact with, said circular polycrystalline colloid monolayer obtained in step d) or optional step e), wherein the volume of said droplet is 15 μL or less and the contact angle of said droplet on said solid substrate is preferably in the range of 20° to 120°; h) protecting the upper surface of the solid substrate obtained in step g) from airflow and turning the solid substrate upside down; i) maintaining the solid substrate in the upside-down position to evaporate the at least one droplet of aqueous dispersion (B); and then j) optionally, flipping the solid substrate obtained in step i) into the correct orientation; The method of any one of claims 7 to 12, further comprising:

14. 14. The method according to any one of claims 7 to 13, wherein step d) and / or optional step i) is carried out until the aqueous medium of the droplets of aqueous dispersion deposited in step b) and optional step g), respectively, has completely evaporated.

15. 15. The method according to any one of claims 7 to 14, wherein optional step e) and / or optional step j) is carried out before complete evaporation of the aqueous medium of the droplets of aqueous dispersion deposited in step b) and / or optional step g), respectively.

16. 16. The method according to any one of claims 7 to 15, further comprising the step of transferring said at least one circular polycrystalline colloidal monolayer obtained in step d) or optional steps e), i) or j) preferably onto a polymer film.

17. Use of an assembly according to any one of claims 1 to 6 for labelling an article of interest by direct deposition or preferably by transfer onto a polymer film.

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