Paillettes and methods of making paillettes

Abstract

A film (2000a, 2000b) formed from a self-assembled microstructure of anisotropic nanocrystals is described. The membrane (2000a, 2000b) has an upper surface (2011), a lower surface (2010), a center of mass (2008), and a perimeter (2009). In a first type of film (2000a), the film (2000a) itself is bent back (2013) around a majority of the perimeter (2009). A second type of film (2000b) is shaped so as to move around any point on the periphery (2009) from the upper surface (2011) to the lower surface (2010), a minimum radius of curvature (rmin) being at least 0.1 times the thickness of the film (2000b) at the center of mass (2008).

Description

Field of the Invention

[0001] The present disclosure relates to films formed from self-assembled microstructures of anisotropic nanocrystals, articles including such films, and methods for forming the films and articles. In other applications, the films can be used to provide sequins or bio-iridescent sequins and methods for manufacturing the sequins, such as biodegradable sequins made from cellulose-based materials (e.g., cellulose nanocrystals (CNC)). Background Art

[0002] Embroidery is an art of using additional materials to decorate textiles to enhance the quality of the final garment. The materials are most commonly applied in the form of beads, sequins, threads, gemstones, and crystals. Through design and various application techniques, these materials can transform textiles, enhancing aesthetic, tactile, or functional qualities and / or adding cultural significance and purpose.

[0003] Sequins (pailettes or spangles) are small decorative shiny discs of various shapes and sizes, typically sewn in large numbers onto clothing to produce a shimmering effect. These discs were originally made of metal and served as strong cultural symbols.

[0004] However, with the development of technology, industrial mining, and machinery, sequins are now commonly made of low-cost plastics.

[0005] The essence of sequins is to shine. Once an alluring quality affordable only to the upper echelons of society, it has now become a mass commodity due to the low cost and formable nature of modern plastics. The luster can be mimicked by using petroleum and various iridescent coatings derived from similar chemical mixtures.

[0006] The most widely used sequins are mainly made of PVC (polyvinyl chloride) or PET (polyethylene terephthalate). These plastics are chemical polymers derived from petroleum. They have various surface treatments, such as matte, silk, two-tone, pearl, mirror, metallic, and iridescent.

[0007] In 2017, Ellen MacArthur released a research report: A New Textiles Economy: Redesigning Fashion’s Future, which raised issues regarding the use of petrochemicals in the textile industry and the leakage of microplastics into the environment. The report stated that in the past decade, "the life cycle of PVC (its production, use, and disposal) leads to the release of toxic chlorine-containing chemicals. These toxins accumulate in water, air, and the food chain, causing serious health problems, including cancer, immune system damage, and hormone disruption."

[0008] When considering the size of some types of sequins (the diameter can be less than 5 mm), they belong to the category of microplastics together with the microbeads in cosmetics and glitter powder. "Microplastics are tiny plastic fragments. Different studies have different definitions of their size, but the most common is to define them as having a maximum size of 5 millimeters." (Ellen MacArthur )

[0009] "Studies have shown that the negative impacts of small plastic particles are mainly because they can be digested by aquatic organisms throughout the food chain. It has been proven that the ingestion of microplastics can cause hunger and growth retardation in some species and can release substances of concern by breaking down in the digestive system" (Ellen MacArthur ). "Without clear understanding of their long-term impacts, the widespread pollution of the oceans by microplastics is becoming a major concern. Given the severity of global ocean pollution, some people refer to the current period of human activity as the Plasticine rather than the Anthropocene and describe the world's oceans as a 'plastic soup'."

[0010] Current attempts to make more sustainable sequins include the limited production of cellulose sequins by Langlois-Martin products (https: / / www.pailletteslangloismartin.fr / en / home-page / ) and the production of sequins from food waste (http: / / www.alicepotts.com / bioplasti c.html and https: / / cqstudio.uk / materialsprojects / excessories-c534m). Lang lois-Martin makes sequins from cellulose acetate, which is converted from cotton or wood fibers (80% of the composition) added to a solvent (20%), and the solvent mainly evaporates during the process. The Sustainable Sequin Company also makes sequins from recycled polyester and is seeking to make sequins from compostable bioplastics (https: / / futurefashionfac tory.org / a-new-solution-for sustain-sequins / ).

[0011] Meert et al. from Ghent University in Belgium found in 'Taking a shine to it: How the preference for glossy stems from an innate need for water' JCP 2014 that through a series of experiments, "the preference for gloss and sparkle stems from an innate need for the resource of water." The desire for shiny and vivid color effects is deeply rooted in our human instincts and is thus an important ingredient in countless industrial products (packaging / cosmetics / textiles / paints / automobiles). Besides sequins, these shiny materials come in various forms, such as components, glitter, confetti, pigments, paints, inks, coatings, foils, and flakes. The industry needs sustainable-source, recyclable, biodegradable, and recyclable plastic and metal alternatives to continue to provide colorful effects for consumers while complying with the UN-Sustainable Development Goals and emerging environmental policies.

[0012] US 5,629,055 A describes a solid film with novel optical properties produced from a colloidal suspension of cellulose crystals.

[0013] Cellulose nanocrystals are rod-shaped nanoparticles extracted from cellulose. Cellulose nanoparticles can be dispersed in water to produce chiral nematic liquid crystals, and these structures can be preserved in the solid state. Such nanostructures or microstructures can reflect light in the visible spectrum to produce structural color.

[0014] Zhao et al. in "Printing of Responsive Photonic Cellulose Nanocrystal Microfilm Arrays’ Adv. Funct. Mater. 2018 described the research on producing coatings using cellulose nanocrystals through a blade coating technique. The SEM of the edge described by Zhao et al. showed that the thickness gradually decreased towards the edge of the film. However, in highly ordered films, the edge effect observed by Zhao et al. led to a decrease in the observed structural color intensity relative to the thickness as the periphery was approached because the cholesteric axes remained perpendicular to the substrate. Summary of the Invention

[0015] Aspects of the present invention are described in the independent claims, and optional features are stated in the dependent claims. Aspects of the present invention can be provided in combination with each other, and features of one aspect can be applied to other aspects.

[0016] According to a first aspect of the present invention, there is provided a film formed from a self-assembled microstructure of anisotropic nanocrystals and having a centroid and a perimeter, wherein around most of the perimeter, the film itself bends back.

[0017] The perimeter may correspond to the contour of the projection of the film onto a plane perpendicular to the film thickness at the centroid.

[0018] The film does not enclose a volume. The film may bend back itself in a transverse plane parallel to the film thickness at the corresponding point of the perimeter. The film may bend back itself by a distance of at least 0.1 times the film thickness at the centroid. The film may bend back itself by a distance of at least 0.2 times the film thickness at the centroid. The film may bend back itself by a distance of at least 0.5 times the film thickness at the centroid.

[0019] In this way, the presence of sharp or thin edges at the perimeter can be avoided. Therefore, crack initiation / propagation can be suppressed at the perimeter (which may correspond to the maximum stress in many loading cases). The film produced by this edge effect may be less likely to break or crack than films previously formed from self-assembled microstructures of anisotropic nanocrystals. The curved-back (or "re-curved") portion may still terminate in a sharp / thin edge.

[0020] The film of the first aspect may include features corresponding to any of the features of the method of the sixth aspect. The definitions applicable to the method (or its features) of the sixth aspect may equally apply to the film (or its features) of the first aspect.

[0021] According to a second aspect of the present invention, there is provided a film formed from a self-assembled microstructure of anisotropic nanocrystals and having an upper surface, a lower surface, a centroid and a perimeter, wherein, moving from the upper surface to the lower surface around any point on the perimeter, the minimum radius of curvature is at least 0.1 times the film thickness at the centroid.

[0022] The perimeter may correspond to the contour of the projection of the film onto a plane perpendicular to the film thickness at the centroid.

[0023] Similar to the film of the first aspect, in the film of the second aspect, the presence of sharp or thin edges at the perimeter can be avoided. Therefore, crack initiation / propagation can be suppressed at the perimeter (which may correspond to the maximum stress in many loading cases). The film produced by this edge effect may be less likely to break or crack than films previously formed from self-assembled microstructures of anisotropic nanocrystals.

[0024] The film of the second aspect may include features corresponding to any of the features of the method of the sixth aspect. The definitions applicable to the method (or its features) of the sixth aspect may equally apply to the film (or its features) of the second aspect.

[0025] The following optional features apply equally to the film of the first aspect and / or the film of the second aspect (and / or the article containing any of the films).

[0026] The anisotropic nanocrystals can have a volume fraction of at least 70 wt% of the self-assembled microstructure. The anisotropic nanocrystals can have a volume fraction of at least 80 wt% of the self-assembled microstructure. The anisotropic nanocrystals can have a volume fraction of at least 90 wt% of the self-assembled microstructure. The anisotropic nanocrystals can be uniformly distributed throughout the volume of the film.

[0027] The film can be formed as a single piece by drying a suspension containing anisotropic nanocrystals. By examining the orientation arrangement of the anisotropic nanocrystals, the origin of the film formed as a single piece by drying a suspension containing anisotropic nanocrystals can be determined. This orientation arrangement can be determined in a variety of ways, including but not limited to:

[0028] · Microscopic examination of the fracture surface;

[0029] · Microscopic examination of the cross-section (e.g., polished); or

[0030] · When the film is at least partially transparent, by examining the film using visible light between crossed polarizers.

[0031] When the edge effect in the orientation arrangement of the anisotropic nanocrystals is substantially similar from any point on the periphery towards the centroid, the film is formed as a single piece by drying a suspension containing anisotropic nanocrystals. If this is not the case, it indicates that the film has been cut from a larger object (in doing so, some edge-affected regions are removed).

[0032] The film can be formed by drying within a mold. The mold can be flexible, e.g., made of silicone rubber. The mold can be rigid. The mold can be formed by embossing the surface. The mold can be formed by de-bossing the surface. Alternatively, the film can be formed on a 2D mold in the form of a flat surface that has a region wettable by the suspension, which is defined by a surrounding region non-wettable by the suspension. For example, when the suspension is aqueous, the 2D mold can include a hydrophilic region onto which the suspension is applied to form the film by drying, and the hydrophilic region is surrounded by a hydrophobic region defining the periphery of the film.

[0033] The self-assembled microstructure of the anisotropic nanocrystals can exhibit structural color.

[0034] The pitch of the self-assembled microstructure of anisotropic organic nanocrystals can be in the visible wavelength range, about 400 - 700 nm, and can exhibit structural color. The pitch of the self-assembled microstructure of anisotropic organic nanocrystals can be in the near-infrared and infrared wavelength ranges, about 700 - 1000 nm, thereby reflecting light of these wavelengths. The pitch of the self-assembled microstructure of anisotropic organic nanocrystals can be in the ultraviolet and near-ultraviolet wavelength ranges, infrared, thereby reflecting back light of these wavelengths.

[0035] The self-assembled microstructure of anisotropic nanocrystals can include one or more pigments. The term pigment in this article also encompasses dyes. The film can contain a mixture or blend of two or more pigments. The pigment can be inorganic or organic. The film can have a color that is partially produced by the structural color of the self-assembled microstructure of anisotropic nanocrystals and partially produced by one or more pigments. Any or all of the pigments can be included in the anisotropic nanocrystals. Any or all of the pigments can be located outside the anisotropic nanocrystals, such as in an additive component.

[0036] Alternatively, when the film contains one or more pigments, the self-assembled microstructure of anisotropic nanocrystals may not exhibit structural color.

[0037] The self-assembled microstructure of anisotropic nanocrystals can include one or more additives. One or more additives can include a plasticizer. One or more additives can include sorbitol, preferably sorbitol. One or more additives can include a crosslinking agent. The additive can include a high-contrast absorbent, such as for example carbon black, graphite, graphene, or graphene oxide.

[0038] One or more additives can include an oil. One or more additives can include a wax. The oil or wax can be distributed within the self-assembled microstructure of anisotropic nanocrystals. The oil or wax can form or be used as a coating for the film. The oil or wax can be encapsulated by another material or chamber. The oil can be synthetic or natural, such as vegetable oil, seed oil, silica-based oil, etc. The wax can be synthetic or natural, such as paraffin wax, rice bran wax, beeswax, carnauba wax, etc.

[0039] One or more additives can include at least one type of inorganic particle.

[0040] One or more additives can include fibers. The fibers can be cellulose fibers, and the anisotropic nanocrystals can be cellulose nanocrystals.

[0041] One or more additives may include at least one polymer. The polymer may be a biopolymer. The polymer may act as a plasticizer. The polymer may serve to provide cross-linking between anisotropic nanocrystals. The polymer may take the form of a matrix in which the anisotropic nanocrystals are embedded. The polymer may have the same monomer units as the anisotropic nanocrystals.

[0042] The membrane may be mechanically self-supporting. The membrane may not be supported on a substrate. In other words, the membrane may be free-standing.

[0043] The membrane may include one or more through-holes. The through-holes may be circular. Alternatively, the through-holes may be square, rectangular or any other regular or irregular shape. The through-holes may be formed integrally when forming the membrane, rather than being cut, drilled or punched after forming the membrane.

[0044] The self-assembled microstructure of the anisotropic nanocrystals may reflect light of a target wavelength. The properties and distribution of the anisotropic nanocrystals and the formation of the self-assembled microstructure can be controlled so as to produce a spacing of the anisotropic nanocrystals that is coupled to the light of the target wavelength by diffraction. The target wavelength may be within the visible wavelength range. The target wavelength may be within the infrared wavelength range. The target wavelength may be within the ultraviolet wavelength range.

[0045] The anisotropic nanocrystals may be organic. The anisotropic nanocrystals may be inorganic.

[0046] The anisotropic nanocrystals may be formed from a biopolymer. The membrane may be biodegradable. The anisotropic nanocrystals may be biodegradable. The membrane may be compostable. The membrane may be recyclable.

[0047] The anisotropic nanocrystals may be cellulose nanocrystals. The anisotropic nanocrystals may be bacterial cellulose nanocrystals. The anisotropic nanocrystals may be neutralized cellulose nanocrystals. The anisotropic nanocrystals may be chitin nanocrystals. The anisotropic nanocrystals may be silica nanocrystals. The anisotropic nanocrystals may be silicon nanocrystals. The anisotropic nanocrystals may be silica / silicon nanocrystals. The anisotropic nanocrystals may be polystyrene. The anisotropic nanocrystals may be a mixture of the foregoing materials.

[0048] The membrane may have a shape that is circular, oval, triangular, square, rectangular or any other regular or irregular shape. The membrane may have a shape corresponding to letters, numbers, symbols, logos, etc.

[0049] The membrane may generally be planar or film-like. The membrane may have a film shape conforming to the surface of a three-dimensional shape. For example, it is formed by drying a suspension of anisotropic nanocrystals in a mold having a corresponding shape.

[0050] The article may include a film of the first or second aspect supported on a substrate. The substrate may be a thin film. The substrate may be a sheet. The substrate may be a plate. The substrate may be the surface of a three-dimensional object. The substrate may be a second film of the same type. The substrate may be a porous material. The porosity may be closed pores. The porosity may be open pores.

[0051] The substrate may comprise or be formed of a polymer such as polylactic acid, alginate, polycaprolactone, cellulose acetate, and other biopolymers. The substrate may comprise or be in the form of paper or card. The substrate may comprise or be in the form of a fabric. The fabric may be synthetic, natural, non-woven or woven, such as cotton, linen, hemp, viscose, lyocell, modal, silk, leather, chiffon, rayon, elastane, nylon, and blended fabrics. The substrate may comprise or be in the form of a fiber mat. The substrate may comprise or be in the form of a laminate. The substrate may comprise or be in the form of metal. The substrate may comprise or be in the form of glass.

[0052] The article may include a film of the first or second aspect bonded between a first layer and a second layer. The article may be in the form of a laminate. The first layer may be in any of the forms described above for the substrate. The second layer may be in any of the forms described above for the substrate. The first layer and the second layer may be formed of the same material. The first layer and the second layer may be formed of different materials.

[0053] The article may include a film of the first or second aspect and may also include a coating covering at least one surface of the film. The coating may provide a barrier layer protecting the self-assembled microstructure of the anisotropic nanocrystals from moisture and / or other environmental factors. The coating may alter or enhance the mechanical properties of the film, for example, by increasing rigidity, by filling cracks, etc. The surface of the film not covered by the coating may be bonded to or supported on the substrate described above.

[0054] The coating may encapsulate most of the surface of the film. The coating may encapsulate at least 90% of the surface of the film. The coating may encapsulate the entire surface of the film.

[0055] The article may include a film of the first or second aspect embedded in a transparent material. For example, the film may be embedded in a transparent epoxy resin.

[0056] The film according to the first and / or second aspect, or an article comprising such a film, can be used to provide (but is not limited to) sequins, glitter, jewels, gemstones, jewelry, costume jewelry, pendants, colored ornaments, earrings, buttons, stickers, flash chips, cubic zirconias, thermoset crystals, ornaments, beads, nail art, glass stickers, decorative coatings, confetti, labels, tokens, tinsel, or any other type of object that is used or applied to provide a specular reflection, sparkle, metallic color, bright color, metallic luster pearlescence, holographic, iridescent, or similar effect to an object.

[0057] The film according to the first and / or second aspect, or an article comprising such a film, can also be used to provide (but is not limited to) jigsaw puzzle pieces, coasters, poker chips, trading cards, game pieces, and the like.

[0058] The film according to the first and / or second aspect, or an article comprising such a film, can be applied to a fabric or other surface by applying a suspension comprising anisotropic nanocrystals using a screen printing process, a dot matrix printing process, an inkjet printing process, a flexographic printing process, a gravure printing process, a lithographic printing process, or the like.

[0059] The film according to the first and / or second aspect, or an article comprising such a film, can be used as an alternative to a foil layer for fabrics, papers, cards, and the like.

[0060] According to a third aspect of the present invention, there is provided a method of forming a film, which includes dispensing a volume of a suspension into a mold or a template. The suspension comprises a suspension of anisotropic nanocrystals in a solvent. The method further includes drying the dispensed suspension to form a film having a self-assembled microstructure with anisotropic nanocrystals and having a centroid and a perimeter, wherein around most of the perimeter, the film itself bends backward.

[0061] The method of the third aspect can include features corresponding to any features of the film according to the first and / or second aspect, or an article comprising such a film. The definitions applicable to the film (or its features) of the first and / or second aspect can equally apply to the method (or its features) of the third aspect.

[0062] The method of the third aspect can include features corresponding to any features of the method according to the sixth aspect. The definitions applicable to the method (or its features) of the sixth aspect can equally apply to the method (or its features) of the third aspect.

[0063] According to a fourth aspect of the present invention, there is provided a method of forming a film, which includes dispensing a volume of a suspension into a mold or onto a template. The suspension includes a suspension of anisotropic nanocrystals in a solvent. The method further includes drying the dispensed suspension to form a self-assembled microstructure having anisotropic nanocrystals and a film having an upper surface, a lower surface, a centroid, and a perimeter, wherein moving from the upper surface to the lower surface around any point on the perimeter, the minimum radius of curvature is at least 0.1 times the film thickness at the centroid.

[0064] The method of the fourth aspect may include features corresponding to any features of the film of the first and / or second aspects, or an article comprising such a film. Definitions applicable to the film (or its features) of the first and / or second aspects may equally apply to the method (or its features) of the fourth aspect.

[0065] The method of the fourth aspect may include features corresponding to any features of the method of the sixth aspect. Definitions applicable to the method (or its features) of the sixth aspect may equally apply to the method (or its features) of the fourth aspect.

[0066] The following optional features equally apply to the method of the third aspect and the method of the fourth aspect.

[0067] The method may include dispensing a volume into each of two or more molds to form an array. All the molds may be the same, but this is not necessary. When the molds are different, different volumes of the suspension may be dispensed corresponding to each different type, shape, or volume of the mold.

[0068] The method may include dispensing a volume into each of two or more templates to form an array. All the templates may be the same, but this is not necessary. When the templates are different, different volumes of the suspension may be dispensed corresponding to each different type or shape of the template.

[0069] The volume of the suspension may be dispensed into a mold having a wall height less than or equal to 3 mm. The volume of the dispensed suspension may be greater than the volume that can be accommodated up to the mold wall height. In other words, the mold may be overfilled. Surface tension may prevent the dispensed volume from spilling out of the mold and may hold the suspension in the mold area.

[0070] The mold may be flexible. The mold may be made of silicone rubber. Alternatively, the mold may be rigid.

[0071] The mold can be formed from any material having a surface energy with the anisotropic nanocrystals such that self-assembled microstructures preferentially form energetically at the air-suspension-mold interface (edge / 1-D interface) relative to the suspension-mold interface (surface / 2-D interface). The mold can be formed from any material having poor adhesion to the self-assembled microstructures of the anisotropic nanocrystals, such as a contact angle greater than or equal to 50°.

[0072] The volume of the suspension can be dispensed into a mold or template formed by convex or concave imprinting of a first substrate.

[0073] The first substrate can be formed from any material having a surface energy with the anisotropic nanocrystals such that self-assembled microstructures preferentially form energetically at the air-suspension-second substrate interface (edge / 1-D interface) relative to the suspension-second substrate interface (surface / 2-D interface). The first substrate can be formed from any material having poor adhesion to the self-assembled microstructures of the anisotropic nanocrystals, such as a contact angle greater than or equal to 50°.

[0074] The first substrate can be a thin film. The first substrate can be a sheet. The first substrate can be a plate. The first substrate can be the surface of a three-dimensional object. The first substrate can be a second film of the same type.

[0075] The first substrate can be a porous material. The porosity can be closed pores. The porosity can be open pores.

[0076] The first substrate can comprise a polymer or be formed from a polymer. The first substrate can comprise paper or card or be in the form of paper or card. The first substrate can comprise fabric or be in the form of fabric. The first substrate can comprise a fiber mat or be in the form of a fiber mat. The first substrate can comprise a laminate or be in the form of a laminate. The first substrate can comprise metal or be in the form of metal. The substrate can comprise glass or be in the form of glass.

[0077] The volume of the suspension can be dispensed into a template including a first region of a second substrate that the suspension will wet, the first region being surrounded and defined by a second region that the suspension will not wet.

[0078] If the contact angle of the suspension droplet on a certain region is less than or equal to 90°, it can be considered that the suspension will wet the region. If the contact angle of the suspension droplet on a certain region is greater than 90°, it can be considered that the suspension will not wet the region.

[0079] For example, when the suspension is aqueous, the 2D mold can include a hydrophilic region onto which the suspension is applied to form a film by drying, the hydrophilic region being surrounded by a hydrophobic region defining the film perimeter.

[0080] The second substrate can be formed of any material having a surface energy with the anisotropic nanocrystals such that self-assembled microstructures are preferentially formed energetically at the air-suspension-second substrate interface (edge / 1-D interface) relative to the suspension-second substrate interface (surface / 2-D interface). The second substrate can be formed of any material having poor adhesion to the self-assembled microstructures of the anisotropic nanocrystals, such as a contact angle greater than or equal to 50°.

[0081] The second substrate can be a thin film. The second substrate can be a flake. The second substrate can be a plate. The second substrate can be the surface of a three-dimensional object. The second substrate can be a second film of the same type.

[0082] The second substrate can be a porous material. The porosity can be closed pores. The porosity can be open pores.

[0083] The second substrate can comprise or be formed of a polymer. The second substrate can comprise or take the form of paper or card. The second substrate can comprise or take the form of a fabric. The second substrate can comprise or take the form of a fiber mat. The second substrate can comprise or take the form of a laminate. The second substrate can comprise or take the form of a metal. The substrate can comprise or take the form of glass.

[0084] The suspension can contain one or more pigments. The suspension can include a mixture or blend of two or more pigments. The pigments can be inorganic or organic. The resulting film can have a color produced in part by the structural color of the self-assembled microstructures of the anisotropic nanocrystals and in part by one or more pigments. Any or all of the pigments can be included within the anisotropic nanocrystals. Any or all of the pigments can be located outside the anisotropic nanocrystals, such as in an additive component.

[0085] The suspension can contain one or more additives. One or more additives can include a plasticizer. One or more additives can include sorbitol, preferably sorbitol. One or more additives can include a cross-linking agent. One or more additives can include a high-contrast absorber, such as, for example, carbon black, or black algae, graphite, graphene, etc.

[0086] One or more additives can include at least one type of inorganic particle.

[0087] One or more additives can include an oil. One or more additives can include a wax. The oil or wax can be distributed within the self-assembled microstructures of the anisotropic nanocrystals. The oil or wax can form or be used as a coating of the film. The oil or wax can be encapsulated by another material or chamber. The oil can be synthetic or natural, such as vegetable oil, seed oil, silica-based oil, etc. The wax can be synthetic or natural, such as paraffin wax, rice bran wax, beeswax, carnauba wax, etc.

[0088] One or more additives may include fibers. The fibers may be cellulose fibers, and the anisotropic nanocrystals may be cellulose nanocrystals.

[0089] One or more additives may include at least one polymer. The polymer may act as a plasticizer. The polymer may serve to provide cross-linking between the anisotropic nanocrystals. The polymer may take the form of a matrix in which the anisotropic nanocrystals are embedded. The polymer may have the same monomer units as the anisotropic nanocrystals.

[0090] One or more additives may include two or more polymer precursors that react in suspension to form a polymer. One or more polymer precursors may be added to the suspension immediately prior to dispensing the suspension into a mold or onto a template. The polymer precursors may react to form a polymer concurrently with the drying of the suspension.

[0091] The mold or template may also include one or more through-hole structures that are arranged such that the resulting film includes through-holes corresponding to each through-hole structure. The through-hole structures may be circular. Alternatively, the through-hole structures may be square, rectangular, or any other regular or irregular shape.

[0092] The anisotropic nanocrystals may be formed from a biopolymer.

[0093] The film may be biodegradable. The film may be compostable. The anisotropic nanocrystals may be biodegradable.

[0094] The anisotropic nanocrystals may be cellulose nanocrystals. The anisotropic nanocrystals may be bacterial cellulose nanocrystals. The anisotropic nanocrystals may be neutralized cellulose nanocrystals. The anisotropic nanocrystals may be chitin nanocrystals. The anisotropic nanocrystals may be silica nanocrystals. The anisotropic nanocrystals may be silicon nanocrystals. The anisotropic nanocrystals may be silica / silicon nanocrystals. The anisotropic nanocrystals may be polystyrene. The anisotropic nanocrystals may be a mixture of the foregoing materials.

[0095] The suspension may be an aqueous suspension containing 2 wt% cellulose nanocrystals.

[0096] During the drying of the suspension, the temperature may be maintained between 18 °C and 25 °C.

[0097] During the drying of the suspension, the humidity may be maintained between 48% and 65%.

[0098] The method may further include subjecting the dispensed suspension to a constant, uniform air flow.

[0099] The method may also include subjecting the dispensed suspension to a patterned or unpatterned electric field during drying. When the suspension exhibits liquid crystal properties, the anisotropic nanocrystals can be locally aligned with the electric field, resulting in a controllable pattern in the structural color of the film.

[0100] The film can be detached from the mold or template. The method may also include removing the dried film from the mold or template.

[0101] The film can be dried and can remain adhered to a third substrate. Before dispensing the suspension, the third substrate can be received in the mold. The template can include or take the form of the third substrate.

[0102] The third substrate can be a thin film. The third substrate can be a sheet. The third substrate can be a plate. The third substrate can be the surface of a three-dimensional object. The third substrate can be a second film of the same type.

[0103] The third substrate can be a porous material. The porosity can be closed pores. The porosity can be open pores.

[0104] The third substrate can include or be formed of a polymer, such as polylactic acid, alginate, polycaprolactone, cellulose acetate, and other biopolymers. The third substrate can include or take the form of paper or card. The third substrate can include or take the form of fabric. The fabric can be synthetic, natural, non-woven or woven, such as cotton, linen, hemp, viscose, lyocell, modal, silk, leather, chiffon, rayon, spandex, nylon, and blended fabrics. The third substrate can include or take the form of a fiber mat. The substrate can include or take the form of a laminate.

[0105] According to a fifth aspect of the invention, there is provided a method that includes wetting a film according to the first or second aspect (and / or produced by the method according to the third or fourth aspect) with a second solvent. The method also includes contacting the film with the surface of an object. The method also includes drying the second solvent such that the film adheres to the surface of the object.

[0106] The second solvent can be the same solvent as that used in drying the suspension from which the film is formed.

[0107] The method of the fifth aspect can include features corresponding to any features of the film of the first and / or second aspect, or articles containing such film. The definitions applicable to the film (or its features) of the first and / or second aspect can equally apply to the method (or its features) of the fifth aspect.

[0108] The method of the fifth aspect may include features corresponding to any features of the methods of the third and / or fourth aspects. The definitions applicable to the methods (or their features) of the third and / or fourth aspects may equally apply to the method (or its features) of the fifth aspect.

[0109] The method of the fifth aspect may include features corresponding to any features of the method of the sixth aspect. The definitions applicable to the method (or its features) of the sixth aspect may equally apply to the method (or its features) of the fifth aspect.

[0110] Compared with the conventional techniques for producing sequins, the sequins of the present disclosure are made of cellulose nanocrystals (CNC), which due to the way the CNC assembles when drying, results in structural coloration. This means that luster and vivid colors can be achieved without using pigments, minerals or metals, thus enabling a process using less resource-intensive materials.

[0111] In addition, this means that the sequins of the present disclosure can be biodegradable.

[0112] In addition, although pigments can be added to obtain colors, this is not necessary for producing iridescence. From the perspectives of formulation and cost, not having to add additional pigments is beneficial. Previously, decorative components made of cellulose acetate (or other bioplastics) required the addition of colorants and glitter agents. Moreover, working with CNC means that non-toxic solvents (such as water) can be used as the evaporation matrix instead of toxic solvents.

[0113] In addition, the sequins of the present disclosure can be made by casting in a mold rather than punching from a sheet material. By not punching from a sheet material, this can reduce waste (by up to 33% on average), because the punched-out sequins leave behind the pierced sheet material (sometimes called Punchinella), which has no viable use.

[0114] There are other advantages to making sequins by casting in a mold. Using a precision mold causes the CNC material to take shape / form a shape during self-assembly (when the casting liquid dries), resulting in fully formed shapes / components that are less brittle than when cut or punched from a sheet material.

[0115] Accordingly, in a sixth aspect of the present disclosure, a method of manufacturing iridescent sequins, such as biodegradable sequins, is provided. The method includes obtaining a suspension of cellulose nanocrystals and a plasticizer dissolved in water, dispensing the suspension into a flexible mold, drying the dispensed suspension at a temperature between 18 °C and 25 °C and a relative humidity between 48% and 65% to produce dried iridescent sequins, and bending the mold to dislodge the dried biodegradable iridescent sequins from the mold. Preferably, the drying time is at least 6 hours, preferably at least 8 hours. When the temperature is 25 °C, the drying time is preferably 6 hours.

[0116] However, it should be understood that in some instances, a flexible mold may not be used. In such instances, the method accordingly does not include the step of bending the mold to dislodge the dried iridescent sequins from the mold. For example, the method may include some other technique for lifting the dried iridescent sequins from the mold, such as using suction / vacuum, possibly in combination with a mechanism for releasing a standing rod (as described below). For example, the rod may be a separate item removable from the mold, such as a pin or nail extending through the mold, but typically preferably, the rod is made of the same material as the rest of the mold to avoid differences in surface tension that can cause the sequins to have undesirable structural properties (such as bending) when drying.

[0117] Advantageously, forming the sequins entirely as separate objects within the mold can produce separate circular colorings (bull's-eye or coffee-ring effects - see, for example, Klockars et al., Asymmetrical coffee rings from cellulose nanocrystals and prospects in art and design, Cellulose 26, 491 - 506 (2019)), which is natural for CNC self-assembly. This effect is unique in the field of sequin iridescent effects. Additionally, this method of forming sequins still allows for the achievement of CNC coloring effects, such as monochromatic or bicolor color changes. Further, producing fully formed shapes can avoid cutting from larger sheets and generating waste. Compared to traditional sequins, the biodegradable sequins of the present disclosure have sustainable sparkle, luster, and vibrant non-fading coloring.

[0118] The mold preferably includes a plurality of containers for receiving the suspension, and each container includes a standing rod made of the same material as the rest of the mold for creating holes in the sequins during drying. The rod is configured to create holes in the sequins during drying for sewing / embroidering the sequins onto clothing or textiles.

[0119] In some instances, each container is circular, but it is understood that other geometric shapes, such as triangular or trapezoidal, can also be used.

[0120] Each container can be circular and have a flat base with a diameter of 10 mm and a wall height or depth of 0.3 - 0.5 mm. The diameter of the rod can be between 0.8 and 1.5 mm, for example 0.8 to 1.2 mm, and preferably 1.2 mm. It has surprisingly been found that 1.2 mm is particularly effective in balancing the need to create holes in the sequin with the structural integrity of both the mold and the resulting sequin. In some instances, the rod is 3 mm from the edge and / or 2 mm from the center. For such dimensions, approximately 200 to 350, preferably 250 to 330 microliters of solution are preferably dispensed into each container (preferably, the solution dispensed into the container is greater than the volume of the container so that the solution forms a domed surface due to surface tension effects.

[0121] This ensures that the suspension forms flat sequins with sufficient structural integrity when dried. It has been found that such dimensions produce uniform films / sequins without raised edges and no deformation around the rod / holes. However, it is understood that sequins of other sizes can be made. For sequins of other sizes, the relative dimensions of the mold / container assembly can remain the same, for example, even if the diameter of the sequin is reduced to 5 mm, the wall height or depth can remain at 0.3 - 0.5 mm. Similarly, the rod can have the same diameter of 1.2 mm as the thread needs to pass through the holes formed in the sequin for sewing / embroidering on clothing, although of course the relative spacing of the rod from the center and the wall can be different.

[0122] The suspension can be dispensed into each container of the mold adjacent to the rod. Advantageously and surprisingly, dispensing the solution adjacent to the rod means that the CNC material self - assembles around the holes for sewing, thus avoiding punching and creating a circular iridescent pattern. In addition, it has been found that dispensing the solution adjacent to the rod can also reduce the likelihood of forming bubbles in the solution, and the formation of bubbles would produce defective sequins.

[0123] The suspension can be a 2 wt% suspension of cellulose nanocrystals. The plasticizer can include, for example, sorbitol and / or glycerol. The ratio of the plasticizer can be 10% of the dry mass of the cellulose nanocrystals. Surprisingly, it has been found that these concentrations of materials produce uniform films / sequins with good coloring.

[0124] In some instances, the suspension also contains a cross - linker.

[0125] In some instances, the suspension further comprises a color dye. The dye can be a food dye, such as food coloring 102, 122 (2.3% of the total dye). The coloring agent is 122, a synthetic red coloring agent belonging to the azo dye class. It is obtained from coal tar and is mainly used in the confectionery industry, while 102 tartrazine is a synthetic lemon yellow azo dye mainly used as a food coloring. Synthetic coloring agents can be used.

[0126] Preferably, 100% natural and plant-based natural food colorings can be used. For example, a yellow pigment made from an extract of real marigold petals (containing water, glycerol, and marigold extract (1.5%)) can be used, or a green pigment made from glycerol and spinach extract (18.7%), for example.

[0127] The concentration depends largely on the dye used and the concentration of the dye in water. Preferably, the concentration can be in the range of about 0.6% to about 2.1% by volume. Roughly speaking, 2 drops of dye (1 ml of dye: 144 ml of CNC) is equivalent to about 0.69%, 4 drops of dye (2 ml of dye: 144 ml of CNC) is equivalent to 1.39%, and 6 drops of dye (3 ml of dye: 144 ml of CNC) is equivalent to 2.07%. Using more than 10 drops (3.45%) may overly change the CNC mixture and affect its assembly when the CNC dries to form sequins.

[0128] The temperature for drying is preferably 23 °C. The humidity for drying is preferably 50%. Surprisingly, it was found that such temperature and humidity can dry the sequins at a slow enough rate to form an aesthetically pleasing iridescent color, and the sequins do not dry too quickly and become too brittle.

[0129] In some instances, the method may further include the step of coating the iridescent sequins in a cellulose material, such as cellulose acetate.

[0130] Drying the dispensed suspension can include subjecting the dispensed suspension to a constant, uniform air flow. Advantageously, this can help ensure that all the sequins in the 15 molds dry at the same time and rate.

[0131] The seventh aspect of the present disclosure is an iridescent sequin made according to the above method.

[0132] The eighth aspect of the present disclosure is an iridescent sequin comprising cellulose nanocrystals and a plasticizer.

[0133] The plasticizer can be sorbitol. The ratio of the plasticizer can be 10% of the dry mass of the cellulose nanocrystals.

[0134] The iridescent sequin may further comprise a crosslinking agent. Description of the Drawings

[0135] Embodiments of the present disclosure will now be described with reference to the accompanying drawings by way of example only, wherein:

[0136] Figure 1 A perspective view of an exemplary mold for sequins is shown, the mold including dry sequins in each of a plurality of containers;

[0137] Figure 2A Shows Figure 1 Another schematic view of the exemplary mold for sequins of

[0138] Figure 2B Shows Figure 2A A cross-section of the exemplary mold for sequins of Figure 2C Shows Figure 2B An enlarged portion of the cross-section of

[0139] Figure 2D Shows Figures 1 to 2C A schematic view of the container of the mold of

[0140] Figure 3 Shows a perspective view of a robot dispensing a suspension into each container of a mold (such as Figure 1 or the mold of FIG. 2);

[0141] Figure 4 A photograph of an exemplary iridescent sequin manufactured according to an embodiment of the present disclosure is shown;

[0142] Figure 5 An exemplary process flow diagram of an exemplary method for making iridescent sequins is shown;

[0143] Figure 6 A graph showing the relationship between drying time, color intensity, and temperature is shown;

[0144] Figure 7 Schematically shows forming a film by dispensing a suspension of anisotropic nanocrystals into a mold;

[0145] Figure 8 Schematically shows forming a film by dispensing a suspension of anisotropic nanocrystals onto a mold;

[0146] Figure 9 Schematically shows forming a film by dispensing a suspension of anisotropic nanocrystals into a mold formed by convex imprinting a substrate;

[0147] Figure 10 Schematically shows forming a film by dispensing a suspension of anisotropic nanocrystals into a mold formed by concave imprinting a substrate;

[0148] Figure 11 is a schematic cross-section of a first type of film;

[0149] Figure 12 is a schematic cross-section of a second type of film;

[0150] Figures 13A to 13G are schematic cross-sections of first to seventh instances of a first type of film;

[0151] Figures 14A to 14F are schematic cross-sections of first to sixth instances of a second type of film;

[0152] Figure 15 depicts instances of a first type of film, having various shapes, positioned between polarizers in different configurations;

[0153] Figure 16 presents a comparison of a film formed according to specifications with a shape physically cut from a sheet having the same formulation under the Figure 15 same conditions;

[0154] Figures 17A to 17D presents, for example, a scanning electron microscope cross-section of a first type of film;

[0155] Figure 18 presents an optical microscopy examination of a first type of cellulose nanocrystal film over an observation angle range from 0° to 50°;

[0156] Figure 19 is for Figure 18 a 3D optical image of the cellulose nanocrystal film shown;

[0157] Figure 20A is a photograph of a second type of cellulose nanocrystal film;

[0158] Figure 20B is Figure 20A a photograph of the cellulose nanocrystal film shown, folded in half to display the cross-sectional shape;

[0159] Figure 21 presents a scanning electron microscope cross-section of a comparative example produced by drying a suspension of cellulose nanocrystals in a petri dish; and

[0160] Figure 22 presents a scanning electron microscope cross-section of a second type of cellulose nanocrystal film. Detailed Description

[0161] The structural color in the present disclosure is caused by the nanostructure (also known as microstructure) of nanoparticles that exhibit a cholesteric order. This structure can be formed by the self-assembly of chiral nematic liquid crystals. Once the critical concentration of nanoparticles is reached under optimal conditions, the nanoparticles begin to form cholesteric helical microstructures. These particles form pseudo-layers perpendicular to the cholesteric axis and parallel to the substrate. The cholesteric pitch is defined by the rotation of the director of these pseudo-layers by 360°. When this pitch is within the visible spectrum, the structural color is observed.

[0162] Figure 1 A perspective view of an exemplary mold 101 for sequins is shown, which includes a suspension dispensed into each of a plurality of containers 103. Figure 1 A mold 101 containing dried sequins is shown.

[0163] In this example, the mold 101 is made of a flexible material such as silicone. When the sequins are dried, the silicone advantageously does not stick to the sequins, facilitating their removal. Although a release agent can be used, it is found that the release agent gives a "matte" effect to the surface finish inside the mold, thus negatively affecting the aesthetic properties of the sequins.

[0164] Figures 2A to 2D A schematic view of the mold 101 and the container 103 is shown. Figures 1 to 2D Each container 103 shown in is circular, but as described above, other shaped containers can also be used. The container 101 is formed by a circular wall 105 protruding from the surface of the mold 101. In this example, this will result in a container 103 whose base is flush with the rest of the mold 101. However, in other examples, the base of the container 103 may not be flat and / or may not be flush with the rest of the mold 101. For example, the base of the container 103 can have indentations or patterns to produce 3D sequins.

[0165] There is a rod 107 inside the container 103, which also stands upright from the base and is parallel to the wall 105 of the container 103. In the example shown, each container 103 has a diameter of 10 mm, a wall height or depth of 0.3 - 0.5 mm, and a wall thickness of 2 mm (the diameter of the inner surface of the wall is 10 mm, and the diameter of the outer surface of the wall is 12 mm). The rod 107 has a diameter of 1.2 mm and is 3 mm away from the edge

[0166] and 2 mm away from the center, as Figure 2D shown in more detail. For containers 103 of these dimensions, preferably about 300 to 330 microliters of solution are dispensed into each container 103. Preferably, a solution greater than the volume of the container is dispensed, resulting in an initially dome-shaped liquid (due to surface tension). Once the suspension dries and the moisture evaporates, flat sequins are formed.

[0167] Figure 1 and the mold 101 shown in FIG. 2 is made of Smooth-On Mold Star purchased from Advanced Materials and cast on an acrylic casting / mold and machined using a computer-controlled CNC (Computer Numerical Control) machine. TM In some instances, vacuum degassing can be employed to remove air bubbles in the mold and also ensure precise shaping of the rods.

[0168] However, in some instances, instead of using a mold made of silicone resin, a substrate that also serves as a mold can be used. Then, the substrate and the CNC are fused, and a cutting mold (designed to match the mold) cuts them into an assembly. At this time, the aqueous CNC can still evaporate and generate a chiral structure color pattern in the mold.

[0169] A perspective view is shown of the robot 150 dispensing the suspension into each container 103 of the mold 101 (such as the mold 101). The suspension contains cellulose nanocrystals (CNC) dissolved in a solvent, which in this case is water. The suspension can contain between 10 wt% and 1 wt% of cellulose nanocrystals. Preferably, the suspension contains 2 wt% of cellulose nanocrystals. A plasticizer is also added to the suspension and in this instance is sorbitol. The plasticizer can be added at a ratio of 10% of the dry mass of the cellulose nanocrystals.

[0170] Figure 3 A perspective view shows the robot 150 dispensing the suspension into each container 103 of the mold 101 (such as Figures 1 to 2D the mold 101). The suspension contains cellulose nanocrystals (CNC) dissolved in a solvent, which in this case is water. The suspension can contain between 10 wt% and 1 wt% of cellulose nanocrystals. Preferably, the suspension contains 2 wt% of cellulose nanocrystals. A plasticizer is also added to the suspension and in this instance is sorbitol. The plasticizer can be added at a ratio of 10% of the dry mass of the cellulose nanocrystals.

[0171] Cellulose nanocrystals from a variety of sources can be used, including nanocrystals generated from a variety of cellulose materials by acid hydrolysis, which include (but are not limited to) wood pulp, filter paper, cotton, and waste cellulose sources. Cellulose nanocrystals can be purchased from commercial suppliers.

[0172] An example of cellulose nanocrystals that can be used is CelluForce NCV100NASD90. These cellulose nanocrystals are extracted from cellulose, the main component of trees and plants, and are a redispersible powder of uniform acyclic nano-sized crystals. Their size, shape, and charge result in unique behavior in suspension. The high chemical reactivity on the crystal surface enables CelluForce to be customized for various applications. The properties of the cellulose nanocrystals are provided in Table 1 below.

[0173] Product form Spray-dried powder Appearance (color) White to off-white powder Density g.cm-3 0.4-0.6 Moisture content Weight % ≤6 Particle size (powder) μm 1-50 Particle size 1 nm <150 Conductivity 1 μS.cm-1 <350 pH 5.0-8.0

[0174] Table 1: Characteristics of Exemplary CNC Materials

[0175] As Figure 3 shown, a customized dispensing robot is used to dispense the suspension. The dispensing robot is configured to dispense a selected volume of liquid into each container.

[0176] For container 103 with a diameter of 10 mm and a wall height or depth of 0.3 - 0.5 mm, preferably 300 μL of the suspension is delivered or dispensed into each container. As Figure 3 seen, due to the surface tension of the suspension, this forms a dome "bubble" 110 of the liquid suspension in each container 103. However, as moisture evaporates from the suspension during the drying process, the size of this dome bubble 110 decreases and a substantially flat solid iridescent glitter is formed. Figure 2B A cross - section of container 103 of the mold 101 filled with the solution is shown.

[0177] Preferably, the suspension can be dispensed adjacent to rod 107 into each container 103 of mold 101, as Figure 2D shown as the preferred dispensing position 111. In the example shown, if rod 107 is considered to be on the y - axis at a distance from the center line, the preferred dispensing position 111 is approximately 1 mm from the center line of container 103 on the x - axis and approximately 3 mm from rod 107 on the y - axis.

[0178] Advantageously and surprisingly, dispensing the solution adjacent to the rod means that the CNC material will self - assemble around the holes for sewing, thus avoiding punching and producing a circular iridescent pattern. In addition, it has been found that dispensing the solution adjacent to the rod can also reduce the likelihood of forming bubbles in the solution, and the formation of bubbles would produce defective glitter.

[0179] Once all containers 103 of mold 101 have been filled, the mold 101 is subjected to a drying process. The drying process is controlled so that it is not too fast, otherwise it will result in poor iridescence of the glitter and it may be more brittle. This is described in more detail below with reference to Figure 6 to be described in more detail.

[0180] It has been found that, preferably, the sequins should be dried at ambient temperature, for example between room temperature of 15° to 25°C, preferably 22°C to 23°C, and even more preferably 23°C. Preferably, the humidity should be kept constant at 48% to 65%, and preferably 50%. Optionally, a uniform air flow can be conveyed above the top of the mold 101 to enhance drying, but it is important that the air flow is uniform, as it has been found that if there is no uniform air flow, the humidity at the center of the mold 101 may be higher and cause the sequins at the edge of the mold 101 to dry faster, resulting in a different iridescent color quality compared to the sequins made at the center of the mold 101. For a fashion company, having sequins with different rainbow color qualities may be unacceptable as in a fashion company, all the sequins on a garment must look the same.

[0181] Alternatively, or as an alternative, the mold 101 can be dried by heating at 40°C, 105°C, and / or 65°C, and then the dried sequins are pressed with a hot press at 200 bar. This makes the sequins flat and shows improved hydrophobic properties. However, the sequins become more brittle during the sewing process.

[0182] It is desirable to have a flexible mold 101 so that the sequins can be easily detached by bending the mold by hand.

[0183] Figure 4 A photograph of an exemplary iridescent sequin 400 manufactured according to an embodiment of the present disclosure is shown. As can be seen in Figure 4 , the iridescent sequin 400 has a natural circular iridescent pattern, which is self-assembled when the CNC suspension dries in the container of the mold. The iridescent sequin 400 also has holes 405 formed by rods 107 in each container 103. The holes 405 advantageously allow a thread to pass through them, so that the sequins can be sewn onto textiles or garments.

[0184] Figure 5 An exemplary process flow diagram of an exemplary method 1000 for making iridescent sequins is shown. In step 1010, a suspension of cellulose nanocrystals and a plasticizer dissolved in water is obtained. In step 1020, the suspension is dispensed into a flexible mold. In step 1030, the dispensed suspension is dried at a temperature between 18°C and 25°C and a relative humidity between 48% and 65% to produce dried iridescent sequins. In step 1040, the mold 101 is bent to detach the dried iridescent sequins from the mold 101.

[0185] In some instances, the brittleness of the sequins can be improved by adding additives, synthetic polymers, or plastics.

[0186] In some instances, rather than forming the sequins in a mold, a thin sheet of CNC material can be formed using a roll-to-roll method and the sequins can be manufactured using conventional punching methods. However, this still results in waste and the material may not meet the mechanical properties required to withstand the impact of the punching machine.

[0187] In some instances, rather than forming the sequins in mold 101, a pre-existing or newly formulated cellulosic plastic sheet (which can be washable) can be used and coated with a non-ferrous metal such as aluminum. This option does not reduce the use of colored pigments or metals and is more resource-intensive than the method described above with reference to Figures 1 to 5 the method described above.

[0188] Another way to form the sequins is to laminate cellulose films (possibly fibrillated cellulose with mechanical properties rather than crystals), where the distance between the layers is selected to be specific so that they refract light and produce structural color. This will produce an overall coloring effect. To simulate the coloring achieved by the iridescent sequins described above with reference to Figures 1 to 5 the method described above, a pigment color inkjet can be used to print on the film to obtain a color ring, or to produce structural color, perhaps a magnet can produce a pattern. Then it must be printed out to match the die-cutting tool.

[0189] As described above, if the sequins dry too quickly, the iridescent effect will be diminished. Figure 6 is a graph of the drying time 603 and color intensity 601 of a 300 μL solution versus temperature at a relative humidity of 10 - 15%, and shows that if the sequins dry at a slow enough rate (in this instance at approximately 20 - 23 °C for approximately 6 hours), the iridescence or perceived color intensity 601 will be improved.

[0190] General case

[0191] While the use of a specific type of flexible mold to form a specific shape (sequins) has been described above, the method and resulting film are not limited thereto. Similarly, while the method described above was described in terms of an aqueous solution of cellulose nanocrystals, the method and resulting film are not limited thereto. Specifically, the physical self-assembly of a suspension confined within a region is not specific to an aqueous solution of cellulose nanocrystals dried within a flexible mold formed of silicone rubber. The same principle can be applied to the self-assembly of microstructures formed from any anisotropic nanocrystals (whether formed from organic materials, inorganic materials, or blends of both) by drying a suspension of these anisotropic nanocrystals in a solvent. The suspension can also be confined to the outline of a desired shape (not limited to sequins) in a variety of ways including using a mold and / or a template.

[0192] In addition, the relative surface energies of the interfaces between the suspension, air, the mold or template, and the self-assembled microstructures can control the shape of the film formed by drying the suspension. Without wishing to be bound by theory, it is believed that this is due to the anchoring of these interfacial energies, thereby controlling the domain orientation to the mold and how it is oriented at the edges. The hydrophobicity of the mold or template results in a higher contact angle and prevents the suspension from depositing on the sides, which results in preventing / reducing the coffee ring effect (capillary flow deposits the material in a ring form at the edge of the droplet) and anchoring on the substrate. As the liquid crystal domains form, grow, and deposit at the interface between the mold and the suspension, the helical axis undergoes continuous changes.

[0193] The mold can be formed of any material having a surface energy with the anisotropic nanocrystals such that self-assembled microstructures preferentially form energetically at the air-suspension-mold interface (edge / 1-D interface) relative to the suspension-mold interface (surface / 2-D interface). The mold can be formed of any material having poor adhesion to the self-assembled microstructures of the anisotropic nanocrystals, such as a contact angle greater than or equal to 50°. Optical tensiometry measurements using a contact angle goniometer can be used to measure the contact angle. The mold can be made of materials and coatings to produce a hydrophobic effect.

[0194] Specifically, the shape or profile of the film around the perimeter can be controlled such that sharp or thin edges at the perimeter can be avoided. Thus, the initiation / propagation of cracks can be inhibited at the perimeter (which may correspond to the maximum stress in many loading cases). The film produced by this edge effect is less likely to break or develop cracks than the films previously formed by the self-assembled microstructures of anisotropic nanocrystals. Examples of the film shapes / edge effects that can be obtained are described below. Figures 11 to 14F Examples of the film shape / edge effects that can be obtained are described.

[0195] A film having a self-assembled microstructure of anisotropic nanocrystals formed in this way will also exhibit an interaction with light similar to that of the previously described iridescent flakes, provided that the typical spacing between the anisotropic nanocrystals is comparable to visible light. In other examples, the spacing can be controlled to cause reflection of structural colors and / or light of invisible wavelengths, such as infrared or ultraviolet wavelengths.

[0196] Reference is also made to Figure 7 、 11 and 12, which illustrate the general case of forming films 2000a, 2000b in a mold 2001.

[0197] For example, using a pipette 2004 (which can be manual or automatic), a certain volume 2002 of suspension 2003 is dispensed into mold 2001. Suspension 2003 includes anisotropic nanocrystals suspended in a solvent. The anisotropic nanocrystals can be bacterial cellulose nanocrystals or neutralized cellulose nanocrystals. Examples of suitable anisotropic nanocrystals other than cellulose include, but are not limited to, chitin, inorganic substances, silicon, silica, polystyrene. Examples of solvents other than water include, but are not limited to, ethanol, glycerol, glycerin, IPA, methanol, acetone.

[0198] Mold 2001 typically takes the form of one or more holes 2005 (or containers), each hole being defined by a wall 2006 standing upright from a base 2007. Wall 2006 can typically be integrally formed with base 2007. However, if a good enough seal can be obtained (either by pressure or otherwise), then after membranes 2000a, 2000b are dried, wall 2006 can be separated from base 2007, for example to facilitate removal. The height h of wall 2006 is typically less than or equal to 3 mm. The height h can be lower or higher, depending on the concentration of suspension 2003. For a concentration of cellulose nanocrystals higher than 2 - 8% by weight, the height h of wall 2006 can be reduced to 0.01 - 2.9 mm, where the height of the hole stem is 0.3 - 3.2 mm, and the diameter D of membranes 2000a, 2000b (such as sequins) is 4 - 12 mm.

[0199] Each hole 2005 (especially the floor / base) can be non - flat, concave, convex, or other shapes. Mold 2001 can be made of different materials, including but not limited to: silicon, PVC, and other resins and polymers (including biopolymers and / or synthetic polymers). Mold 2001 can also be made of glass or metal with a natural or treated surface. Other materials for mold 2001 can include, for example: polystyrene, acrylic, PVC, polyurethane, wood, steel, aluminum, other alloys, paper, cardboard, textiles, composite materials, and different grades of silicone.

[0200] Volume 2002 is preferably greater than the volume defined by the height h of wall 2006, and its overflow 2006 is prevented by the surface tension of suspension 2003. Mold 2001 can be flexible, for example formed from silicone rubber as described above. Alternatively, mold 2001 can be rigid. In some instances, one of base 2007 and wall 2006 can be flexible while the other element is rigid.

[0201] The holes 2005 can be arranged to form an array, and each hole 2005 can be considered as a separate mold 2001 within the meaning of this specification. A plurality of holes 2005 can have the same shape, but this is not necessary, and various hole 2005 shapes (e.g., square, circular, etc.) can be provided on a single base 2007 as needed. When the holes 2005 are different, suspensions 2003 of different volumes 2002 can be dispensed into each hole.

[0202] Then the dispensed volume 2002 of the suspension 2003 is dried to form films 2000a, 2000b of self-assembled microstructures having anisotropic nanocrystals. There are two main cases of interest, which are described separately in Figure 11 and Figure 12 respectively.

[0203] With particular reference to Figure 11 , a schematic cross-section of a first type of film 2000a (hereinafter referred to as the "first film") is shown, which has a "back-bent" edge effect.

[0204] The first type of film 2000a is formed from a self-assembled microstructure of anisotropic nanocrystals and has a centroid 2008 and a perimeter 2009. The lower surface 2010 corresponds to the surface of the first film 2000a formed in contact with the mold 2001, and the upper surface 2011 corresponds to the surface in contact with air after the drying process is completed. The first film 2000a generally has a uniform thickness over a body region 2012 including the centroid 2008. However, around at least most of the perimeter 2009, the first film 2000a itself bends backward to form a back-bent portion 2013.

[0205] The back-bent portion 2013 can have a thickness comparable to that of the body region 2012, but may be thinner or thicker in some cases. The back-bent portion 2013 extends backward (i.e., toward the centroid 2008) from the perimeter 2009 a distance d r , generally parallel to the body region 2012 (on average, since the body region 2012 does not need to be flat). The back-bent portion 2013 is separated from the upper surface 2010 of the body region 2012 to which it bends backward by a distance h s , and in some cases this distance may actually be zero (i.e., in contact).

[0206] When the mold 2001 is circular, the perimeter 2009 will also be circular, and its diameter D generally corresponds to the hole 2005 of the circular mold 2001. In this case, the parameters d r , h s , the overall shape and thickness of the back-bent portion 2013 will generally be consistent around the entire circular perimeter 2009. When the mold 2001 is not circular, but square, rectangular, etc. (see alsoFigure 15 ) When the parameter d r , h s , the overall shape and thickness of the bend-back portion 2013 will generally vary with the position around the perimeter 2009. For example, the midpoint of a square perimeter 2009 will be different relative to the corner points of the same square perimeter 2009. However, under the right conditions (described below), the bend-back portion 2013 will exist around at least most of the perimeter 2009.

[0207] The first film 2000a is generally thin in one dimension, although it does not necessarily have to be flat / plane (and is intentionally non-flat in many applications) and does not enclose a volume. The first film 2000a, particularly its bend-back portion, can bend back on itself by at least a distance equal to the thickness of the film at the centroid 2008 (using the centroid as representative of the body region 2012). When the first film 2000a is not flat, the perimeter 2009 can be determined by projecting the profile of the first film 2000a onto a plane perpendicular to the film thickness at the centroid 2008.

[0208] In this way, sharp or thin edges at the perimeter 2009 can be avoided. Thus, the initiation / propagation of cracks can be inhibited at the perimeter 2009 (which may correspond to the maximum stress in many loading cases). This edge effect results in the first film 200a being less likely to break or develop cracks compared to previous films formed from cellulose nanocrystals (or the like). The bend-back portion 2013 can still terminate in a sharp / thin edge (see also Figure 13A and 13E ) without losing the desired edge effect at the perimeter 2009.

[0209] Without wishing to be bound by theory, the formation of the first film 2000a with the bend-back portion 2013 is thought to be facilitated by a structural alignment continuity that is superior to the structural anchoring to the mold 2001 or the template 2015. Thus, an alignment and continuous direction of the film 2000a is produced, resulting in the bend-back shape, as in Figure 17A , 17BAs can be seen experimentally in FIGS. 16A and 17D. The shape of the film 2000a is different from the shape of the thin films formed in plastic or glass petri dishes in the prior art. In such prior art thin films, anchoring to the petri dish is dominant, producing an edge effect with a sharp change in the helical axis. This typically results in structural weaknesses at the edges, where the thin film redirects to the petri dish wall at a right angle. This is common in the literature, where materials form upwards on the sides of the petri dish; see, for example, Largerwall et al., "Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films" NPG Asia Mater. 2014; and Parker et al., "The Self-Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance", Adv. Mat. 2017. When such thin films are detached (or attempt to be detached) from the petri dish, their edges typically break off from the main thin film. The edge region does not always detach, but due to this defect, there are essentially structural weaknesses.

[0210] With particular reference Figure 12 , a schematic cross-section of a second type of film 2000b (hereinafter referred to as the "second film") is shown, which has a "blunt" edge effect.

[0211] The second film 2000b is substantially the same as the first film 2000a, except that it does not include an edge effect in the form of a bent-back portion 2013. Instead, the cross-sectional profile of the second film 2000b is controlled such that moving from the upper surface 2011 to the lower surface 2010 (or vice versa) around any point on the perimeter 2009, the minimum radius of curvature r min is at least 0.1 times the thickness of the second film 2000b at the centroid 2008 (taken as representative of the bulk region 2012 away from any edge effects). For example, along the Figure 12 path 2014 shown. Figure 12 shows a simple (special) case where the minimum radius of curvature r min is approximately equal to half the thickness of the second film 2000b at the centroid 2008, while Figures 14A to 14F shows a more complex case. In fact, the minimum radius of curvature r min is typically significantly less than half the thickness of the second film 2000b at the centroid 2008, but it should be controlled to be at least 0.1 times that thickness.

[0212] Similar to the first film 2000a, the second film 2000b avoids forming sharp or thin edges at the periphery 2009 (contrary to prior art examples of films formed using cellulose nanocrystals). Thus, crack initiation / propagation can be suppressed at the periphery 2009, making the second film 2000b less likely to break or develop cracks compared to prior art cellulose nanocrystal films (or the like).

[0213] Without wishing to be bound by theory, it is believed that the formation of the second film 2000n with a controlled minimum curvature r min is facilitated by a lateral dimension boundary via a fixed or physical boundary, which in either case limits the thinning / spreading of the material. This may be due to the repulsive force of the die 2001 material and / or the high contact angle generated by the template 2015. The second film 2000b can be formed from anisotropic nanocrystals in the suspension 2003 at a high concentration (e.g., 3 to 10 wt%) because too low a concentration (e.g., below 3 wt%) results in the bulk region 2012 of the resulting film 2000b being too thin. This may cause a change in the angle of the cholesteric axis of the anisotropic nanocrystals at or near the periphery 2009.

[0214] An alternative method of forming the second film 2000b is to first form the first film 2000a, as Figure 11 shown, and then deposit additional material to fill the region inside the back-bent portion 2013 (e.g., one or more cycles of dispensing and drying the suspension 2003), thereby creating the shape of the second film 2000b. This second film 2000b provides a structure without sharp points, weak points, and / or brittle edges around the periphery 2009.

[0215] Above, the use of a die 2001 including one or more holes 2005 or containers 103 to restrict the suspension 2003 during drying to form films 2000a, 2000b of the desired shape has been described. However, the walls 2006 are not necessary, and restriction can be provided in other ways, such as by controlling surface tension / contact angle.

[0216] Reference is also made to Figure 8 which schematically shows in cross-section a template 2015 for forming films 2000a, 2000b.

[0217] Regarding Figure 7 、 11The method described in can be carried out as described above, except that template 2015 is used instead of mold 2001. Template 2015 includes one or more first regions or "wettable" regions of template substrate 2017 that will be wetted by suspension 2003, and each wettable region 2016 is surrounded and defined by one or more intervening second regions or "non-wettable" regions 2018 where suspension 2003 will not be wetted. A desired volume 2002 of suspension 2003 is dispensed onto each wettable region 2016 and is fixed in place by surface energy effects.

[0218] If the contact angle of suspension 2003 when dropped on a region 2016 is less than or equal to 90°, then suspension 2003 can be considered to wet that region 2016. If the contact angle of suspension 2003 when dropped on a region 2018 is greater than 90°, then suspension is considered not to wet that region 2018. For example, when suspension 2003 is aqueous, wettable region 2016 can be hydrophilic and non-wettable region 2018 is hydrophobic.

[0219] A sufficient degree of fixation of suspension 2003 to be used as template 2015 can be provided by a contact angle of 60 - 75° or higher, such as an aqueous suspension 2003 on silicone rubber.

[0220] In Figure 8 the example shown, template substrate 2017 is wettable and non-wettable regions 2018 are defined by applying a thin coating. Of course, depending on the substrate, alternative surface modifications with no perceivable thickness can be used to alter wettability, such as chemical activation, etc.

[0221] Template substrate 2017 can take any suitable form, including but not limited to films, sheets, plates, etc. In some examples, template substrate 2017 can take the form of the surface of a three-dimensional object. In other examples, template substrate 2017 can take the form of second films 2000a, 2000b of the same material. Generally, template substrate 2017 can be porous or non-porous. The porosity can be closed-cell or open-cell (penetration of open-cell porosity can be avoided by controlling the surface energy relative to suspension 2003 and / or by controlling the size of the anisotropic nanocrystals relative to the pores).

[0222] The template substrate 2017 may comprise or be formed from a polymer such as polystyrene, acrylic, polyvinyl chloride, polyurethane, polyimine, etc. The template substrate 2017 may comprise or be formed from a metal such as, for example, steel, aluminum or other alloys (with natural or treated / coated surfaces), provided there is no adverse reaction with the solvent of the suspension 2003. The template substrate 2017 may comprise paper, card, wood, glass, fabric, textiles (synthetic or natural), fiber mats, silicone rubber (various grades), natural rubber or laminates or two or more such materials or be formed from such materials.

[0223] Also refer Figure 9 , in one specific example of implementing the mold 2001, one or more holes 2005 can be formed by embossing the mold substrate 2019 to form an embossed mold wall 2020. The mold substrate 2019 can be of any type or material as described for the template substrate 2017.

[0224] Also refer Figure 10 , in another specific example of implementing the mold 2001, one or more holes 2005 can be formed by debossing the mold substrate 2019 to form a debossed area 2021. Again, the mold substrate 2019 can be of any type or material as described for the template substrate 2017.

[0225] Such an embossed / debossed mold substrate 2019 can be formed to fabricate a mold 2001 intended to be temporary or semi - temporary, allowing the membranes 2000a, 2000b in the designed shape to be directly deposited onto the adjusted mold substrate 2019. In other examples, it may be intended to make the membranes 2000a, 2000b adhere to the embossed / debossed mold substrate 2019.

[0226] Examples of the first membrane

[0227] The structure of the first membrane 2000a can be better understood with reference to some (non - exhaustive) examples.

[0228] Also refer Figure 13A , a schematic cross - section of a first example 2022 of the first membrane 2000a is shown.

[0229] The first example 2022 has a bent - back portion 2013 that tapers down to a thickness less than (and in some embodiments may be much less than) the thickness of the body region 2012 (e.g., taken at the centroid 2008). Nevertheless, due to the edge effect of the bent - back portion 2013, the first example 2022 retains crack - resistant elasticity due to the thickness at the periphery 2009 and the larger radius of curvature.

[0230] Similar to other instances of the first film 2000a (see Figures 13B to 13G ), for example when used in textiles, the bent-back portion 2013 can also prevent the perimeter 2009 of the film 200a from snagging and / or damaging other materials. For use as glitter, this shape can prevent sharp edges, which can be dangerous for use in cosmetics or other products for the skin (e.g., due to micro-abrasion and / or possible displacement into the user's eyes or other sensitive membranes). Damage to the surface of the object to which the first film 2000a (such as the first instance 2022) is applied / coated can also be avoided.

[0231] Also refer to Figure 13B for a schematic cross-section showing a second instance 2023 of the first film 2000a.

[0232] The second instance 2023 has a bent-back portion 2013 that continues to bend back on itself such that the edge recedes and points downward toward the upper surface 2011 of the body region 2012. This can increase rigidity by forming a tubular structure around at least a portion of the perimeter 2009. Additionally, the potentially thinner edge can be protected by bending around the structure.

[0233] In the second instance 2023, the thickness of the bent-back portion 2013 is substantially the same as that of the body region 2012, but this is not necessary. The thickness of the bent-back portion 2013 of the second instance 2023 can be reduced and / or gradually reduced as described in the first instance 2022. The second instance 2023 with a gradually decreasing thickness may still break, but if this occurs, the gradually decreasing and potentially sharp edges will curl toward the body portion 2012 of the corresponding fragment, thereby reducing the likelihood of damage to external materials.

[0234] Also refer to Figure 13C for a schematic cross-section showing a third instance 2024 of the first film 2000a.

[0235] The third instance 2024 has a bent-back portion 2013 that extends backward to the centroid 2008, and its height spacing h s is relatively small (or even negligible / touching) with respect to the thickness of the film 2000a. In other words, the bent-back portion 2013 lies substantially flat on the upper surface 2011 of the body region 2012. This compact profile can help provide higher toughness, prevent cracks from starting / spreading at the perimeter 2009, while minimizing the increase in rigidity of the film 2000a (starting from the second moment of area).

[0236] The shape of the third example 2024 can further improve the mechanical strength at the periphery 2009. In addition, it can also reduce the variation in the helical axis of the anisotropic nanocrystals, which also directly affects the observed structural color. In this way, the variation in the angle of the reflected color with the viewing angle can be reduced. Compared with the first example 2022, the third example 2024 has a flatter shape and less distinct edge contours. When the film 2000a has high flexibility, the third example 2024 may be advantageous, which can be induced in practice by changing the formulation (weight percentage of anisotropic nanocrystals), the thickness of the film 2000a (e.g., 0.5 to 40 μm), the humidity (e.g., 60% or higher), and the drying speed (e.g., 24 hours or longer).

[0237] In the third example 2024, the thickness of the bent-back portion 2013 is substantially the same as that of the body region 2012, but this is not necessary. The thickness of the bent-back portion 2013 of the third example 2024 can be reduced and / or gradually decreased, as described in the first example 2022.

[0238] Also refer to Figure 13D , which shows a schematic cross-section of the fourth example 2025 of the first film 2000a.

[0239] The fourth example 2025 is the same as the third example 2024, except that the first film 2000a is formed in a mold 2001 having a forming base 2007 that defines all or part of the 3D shape. In the example shown, the first part of the body region 2012a forms a first flat face (or facet), which transitions to the second part of the body region 2012b, forming a second angled face or facet. For example, the lower surfaces 2010a, 2010b can have the appearance of a part of a surface having a shape such as a dodecahedron, coidoid, pyramid, sphere, tetrahedron, toroid, or any other curved or polyhedral (regular or irregular) shape.

[0240] The fourth example 2025 has been described with respect to the third example 2024. However, a similar 3D mold shape can be used with any one of the first 2022 and / or second 2023 examples.

[0241] To achieve the 3D shape, the viscosity of the suspension 2003 should be high, and the material selection should promote a certain degree of fixation and / or adhesion of the suspension 2003 and / or the anisotropic nanocrystals to the mold 2001 or the template 2015, so that the self-assembled microstructure of the anisotropic nanocrystals does not deposit on the bottom of the mold.

[0242] Also refer to Figure 13E , which shows a schematic cross-section of the fifth example 2026 of the first film 2000a.

[0243] The fifth example 2026 is the same as the second example 2023, except that it shows a situation where at least a part of the bent-back portion 2013 is damaged, for example, broken due to downward pressure (relative to the shown cross-section), resulting in the bent-back portion 2013 terminating at a fracture surface 2027. As long as the damage does not extend to or exceed the periphery 2009, the edge effect at the periphery 2009 can be retained.

[0244] The fifth example 2026 has been described relative to the second example 2023. However, it is applicable to any one of the first 2022, third 2024, and / or fourth 2025 examples.

[0245] Also refer to Figure 13F , which shows a schematic cross-section of the sixth example 2028 of the first film 2000a.

[0246] Different from the first 2022 to fifth 2026 examples, the body portion 2012 of the sixth example 2028 is not flat or faceted, but has a curvature. The curvature may be caused by shrinkage / residual strain during drying, or may be intentionally introduced by the shape of the mold 2001. This curvature means that structural color reflections can be observed over a wider range of viewing angles. When used to form glitter powder, due to the concave shape, this curvature can also enhance the adhesion of the film 2000a to the skin (or other surfaces) through a suction mechanism.

[0247] Any one of the first 2022 to fifth examples 2026 may include a body portion 2012 with an intentionally or unintentionally curved shape.

[0248] Also refer to Figure 13G , which shows a schematic cross-section of the seventh example 2029 of the first film 2000a.

[0249] The first 2022 to sixth examples 2028 show a bent-back portion 2013 that bends in a single rotational direction - back towards the centroid 2008. In contrast, the bent-back portion 2013 of the seventh example 2029 has a "double bent-back" shape, which first bends backward towards the centroid 2008 and then changes the rotational direction to bend backward towards the periphery 2009.

[0250] Any one of the first 2022 to sixth examples 2028 may include a bent-back portion 2013 with a "double bent-back" shape similar to that of the seventh example 2029.

[0251] The seventh instance 2029 can be advantageous when the first film 2000a has high flexibility, which can be induced by formulation, film thickness, humidity (e.g., 60% or higher), and drying speed (e.g., 24 hours or longer). Particularly slow drying is beneficial for forming a double-bend shape, which causes the suspension to be anchored to the wall of the mold during the first 50% of the drying process, and then the wall collapses but curls slowly, resulting in the "tail" bending in the opposite direction.

[0252] Examples of the second membrane

[0253] The structure of the second film 2000b can be better understood with reference to some (non-exhaustive) instances.

[0254] Also refer to Figure 14A , which shows a schematic cross-section of the first instance 2030 of the second film 2000b.

[0255] The first instance 2030 does not include a bend-back portion 2013, but around the perimeter, the first instance 2030 does include an edge portion 2031 that extends upward (relative to the lower surface 2010) around at least a portion of the perimeter 2009. Although shown as having the same thickness as the body region 2012, the edge portion 2031 can have a reduced and / or gradually decreasing thickness. The edge portion 2031 extends to a height hr above the body region 2012, and this height h r should not exceed about 3 mm. More generally, the height h r is preferably less than or equal to 50 times the thickness of the body region 12 (e.g., represented by the thickness at the centroid 2008).

[0256] The edge portion 2031 can form a corresponding height of the wall 2006, which is located above the thickness of the body region 2012 of the film 2000b. Without being bound by theory, it is believed that the formation of the edge portion 2031 is due to the fixation of the self-assembled microstructure of anisotropic nanocrystals to the edge of the mold 2021, the thickness of the body portion 2012, and / or the drying speed, which occurs when the concentration is 3 - 8 wt% or when using a high-viscosity additive (such as hydroxypropyl cellulose).

[0257] Also refer to Figure 14B , which shows a schematic cross-section of the second instance 2032 of the second film 2000b.

[0258] Figure 12 The second film 2000b shown in min has a minimum radius of curvature r minIt may be less than half of the thickness of the body region 2012, as long as it is at least 0.1 times that thickness.

[0259] The second instance 2032 may also include an edge portion 2031 as described with respect to the first instance 2030.

[0260] The second instance 2032 can be used in applications for forming (wholly or in part) an object, such as glitter, metallic foil, artificial diamonds, confetti, and other free-standing film applications, to achieve a smooth edge. The edge profile of the second instance 2032 can provide an embossed feel (perceived on the human skin) to the coating, thereby imparting an attractive luxurious effect to the coating.

[0261] Also refer to Figure 14C , which shows a schematic cross-section of a third instance 2033 of the second film 2000b.

[0262] The body region 2012 of the third instance 2033 is curved. In the illustrated instance, the schematic cross-section shows an s-shaped curvature, which can be out-of-plane prismatic or can be part of a more complex shape, such as a saddle shape. This curvature may be due to drying / residual strain (although this may be intentional) or the shape of the mold 2001. The film 2000b with curvature can be used to achieve a specific visual effect because at least a portion of the surfaces 2010, 2011 will satisfy the diffraction / reflection conditions of the self-assembled microstructure of the anisotropic nanocrystals over a wider range of viewing / illumination angles.

[0263] Either the first 2030 and / or the second 2032 instance can be modified to have a curved body region 2012.

[0264] A suspension of, for example, 4 - 8 wt% cellulose nanocrystals in a high concentration in an aqueous suspension 2003 can be used to produce a greater curvature of the body region 2012. Additionally or alternatively, the curvature can be enhanced / promoted by including a high-viscosity additive (such as sorbitol, hydroxypropyl cellulose) in the suspension 2003. Additionally or alternatively, the curvature can be enhanced / promoted by drying under oil or at high humidity (e.g., 60% or higher).

[0265] Also refer to Figure 14D , which shows a schematic cross-section of a fourth instance 2034 of the second film 2000b.

[0266] The fourth instance 2034 has a first part of the body region 2012a that is relatively thinner than one or more relatively thicker second parts of the body region 2012b formed around at least a portion of the perimeter 2009. The minimum thickness 2035 of the first part of the body region 2012a may coincide with the centroid 2008, but this is not necessary. This indicates that in some instances, the minimum radius of curvature r min may be greater than the thickness at the centroid 2008 of the membrane 2000b.

[0267] Any one of the first 2030, second 2032, and / or third instances 2033 may be modified to have a relatively thicker second part of the body region 2012b formed around at least a portion of the perimeter 2009.

[0268] The fourth instance 2034 may use less material and have a reduced total membrane 2000b weight while still producing the same thick-edge effect at the perimeter 2009. The fourth instance 2034 may be favored by increasing the coffee-ring effect (whereby capillary flow promotes particle deposition at the droplet edge), by reducing the viscosity of the suspension 2003 by avoiding high-viscosity additive concentrations, or by reducing the weight % concentration of anisotropic nanocrystals (e.g., the weight % concentration of cellulose nanocrystals in the aqueous suspension 2003 is in the range of 0.5 - 4%). This allows for capillary flow. Additionally or alternatively, the fourth instance 2034 may be favored by reducing the drying time (e.g., less than 24 hours for a 2 wt% suspension), reducing the humidity (e.g., between 30 - 50%), increasing the air flow, or increasing the temperature during the drying process (e.g., 25 - 45 °C).

[0269] Also refer Figure 14E , which shows a schematic cross-section of a fifth instance 2036 of the second membrane 2000b.

[0270] The fifth instance 2036 is the same as the third instance 2033, except that the body region 2012 is curved in only a single direction.

[0271] Any one of the first 2030, third 2033, and / or fourth 2034 instances may be modified to have a curvature similar to that of the fifth instance 2036.

[0272] The concave effect exhibited by the fifth instance 2036 results in an increased breadth of the possible viewing angles of the structural color. The glitter powder formed according to the fifth instance 2036 may have better adhesion / retention on the skin (or other surface) due to the concave suction effect. The fifth instance may be promoted by slowing down the drying time and / or using additives with a larger lateral size (such as graphene with a diameter of 200 - 300 nm).

[0273] Also refer to Figure 14F , which shows a schematic cross-section of the sixth instance 2037 of the second film 2000b.

[0274] For 3D shapes (as opposed to flat shapes), a lower repulsive force between the substrate and the suspension is required to allow fixation on the mold 2001 rather than pooling the suspension 2003 at the bottom of the mold 2001. The vertices of these shapes have the same structural continuity at the bends as the edge effects.

[0275] Similar to the fourth instance 2025 of the first film 2000a, the sixth instance 2037 of the second film 2000b is formed in a mold 2001 having a forming base 2007 that defines all or part of a 3D shape.

[0276] The mold 2001 with the forming base 2007 can be used to modify any of the first 2030 to fifth 2036 instances so as to have a sharp transition between the surfaces / facets, and the forming base defines all or part of a 3D shape.

[0277] The membrane is dried into a single piece

[0278] To obtain the beneficial edge effects described herein, each film 2000a, 2000b (and any of its instances) should be formed into a single piece by drying. Cutting the shape from a single large body area 2012 does not produce the relevant edge effects and may also introduce sharp edges / cracks, which will compromise toughness (prevent breakage).

[0279] By examining the directional alignment of the anisotropic nanocrystals, the origin of the films 2000, 2000b formed into a single piece by drying a suspension containing anisotropic nanocrystals can be determined. These will also exhibit edge effects because self-assembly typically propagates inward from the boundaries between air, the mold 2001 / template 2015, and the suspension 2003 rather than occurring simultaneously throughout the suspension 2003. This is similar to the microstructural edge effects that are evident in other systems (such as injection-molded polymers, cast alloys, etc.).

[0280] This microstructural edge effect (as opposed to the shape edge effect described above) will typically (but not uniquely) manifest in the average directional alignment of the anisotropic nanocrystals and can be determined in a variety of ways, including but not limited to:

[0281] · Microscopic examination of the fracture surface (e.g., intentionally produced by breaking);

[0282] · Microscopic examination of the cross-section (e.g., polished);

[0283] ·Determining the orientation (sometimes referred to as "texture") of anisotropic nanocrystals by X-ray crystallography; or

[0284] ·When the film is at least partially transparent, inspecting films 2000a, 2000b by using visible light between crossed polarizers.

[0285] The latter method, i.e., inspecting by using visible light between crossed polarizers, is particularly preferred because it is relatively easy and simple.

[0286] In the case where the edge effect in the alignment of the anisotropic nanocrystals is substantially similar from any point on the periphery towards the centroid, the film is formed as a single piece by drying a suspension containing the anisotropic nanocrystals. If this is not the case, it indicates that the film has been cut from a larger object (doing so will remove some regions affected by the edge).

[0287] Also refer to Figure 15 , examples of films 2000a with recurved edge portions 2013 and various shapes were produced and imaged between polarizers in different configurations.

[0288] Films 2000a of different shapes were produced in corresponding silicone rubber molds 2001, the height h of whose walls 2006 varied between 0.1 - 0.7 cm. In all cases, the suspension 2003 used was 2 wt% cellulose nanocrystals in water, along with 10% dry mass of sorbitol. The drying time was 12 hours.

[0289] As described herein, films 2000a or different shapes all exhibit an edge effect, where the structure varies with the distance from the periphery 2009, indicating that the edge effect can produce films of different shapes and sizes, not limited to circular. The illustrated examples are small (0.7 cm) 2038a, medium (1.25 cm) 2038b, and large (2.5 cm) 2038c square films; small (1 cm) 2039a, medium (2 cm) 2039b, and large (5 cm) 2039c circular films; small (2.5 cm long) 2040a, medium (5 cm long) 2040b, and large (9 cm long) 2040c oval films; and small (1 cm in diameter) 2041a and large (2 cm in diameter) 2041b hexagonal films.

[0290] Through holes ( Figure 15 not labeled in ) are provided near the periphery 2009 or approximately at the centroid 2008.

[0291] In all cases, an edge effect can be continuously (if not uniformly) observed around the periphery 2009 of each film 2000a.

[0292] Also refer to Figure 16 , which shows from having the same asFigure 15 Shapes 2042a and 2042b physically cut out from a thin sheet with the same formulation as the film 2000a shown. For comparison purposes, small circular film 2039a and large hexagonal film 2041b are also depicted. Figure 16 are obtained under the same conditions as Figure 15 the same.

[0293] Differences in material changes for different shapes can be clearly observed. For the hexagonal 2042a and circular 2042b shapes, there is no difference in the interaction of light between the shape edges and the center. In contrast, the edge effects of film 2000a are clearly visible.

[0294] In this way, it is possible to directly distinguish between films 2000a, 2000b formed by drying as a single piece (as described herein) and shapes with similar shapes and thicknesses formed by cutting from a bulk thin film with the same material composition.

[0295] Peripheral shape of the membrane

[0296] Although it is clear from the previous discussion that the films are not limited to circular / sequin shapes, for the sake of clarity, films 2000a, 2000b can have shapes that are circular, oval, triangular, square, rectangular, or any other regular or irregular shape. If desired, films 2000a, 2000b can be formed to have shapes corresponding to letters, numbers, symbols, logos, etc.

[0297] Films 2000a, 2000b can be generally planar or film-like, or can have a film shape conforming to the surface of a three-dimensional shape. For example, films 2000a, 2000b are formed by drying a suspension of anisotropic nanocrystals within a mold having the corresponding shape (see, for example, Figure 13D and 14F ).

[0298] These three-dimensional shapes can subsequently be filled to produce solid shapes with iridescent surface colors. Suitable filling materials include, but are not limited to, polymers such as cellulose acetate.

[0299] Microstructure and volume fraction of anisotropic nanocrystals

[0300] The anisotropic nanocrystals preferably account for at least 80% of the volume fraction of the self-assembled microstructure of films 2000a, 2000b. More preferably, the anisotropic nanocrystals can have at least 90% of the volume fraction of the self-assembled microstructure. Preferably, the anisotropic nanocrystals can be uniformly distributed throughout the volume of films 2000a, 2000b.

[0301] Table 2 lists some examples, as well as examples of secondary materials included in the microstructure (i.e., parts belonging to other than the anisotropic nanocrystals):

[0302]

[0303] Table 2: The "secondary materials" do not necessarily (but can) form the balance of the microstructure, as the films 2000a, 2000b can also include additional additives for the specifically named examples (as described below).

[0304] Due to the arrangement and typical spacing of the anisotropic nanocrystals, the self-assembled microstructure of the anisotropic nanocrystals usually exhibits structural color. In some embodiments, the self-assembled microstructure of the anisotropic nanocrystals can be controlled to exhibit reflection at a desired target wavelength. By controlling the typical spacing of the anisotropic nanocrystals, either effect can be controlled to occur in the visible, infrared, or ultraviolet wavelength ranges.

[0305] The color produced depends on the cholesteric pitch, the orientation of the helical axis, the order of the cholesteric phase, and the wavelength polarization and propagation direction of the incident light

[0306] The anisotropic nanocrystals are capable of self-assembling into a chiral nematic liquid crystal or a cholesteric liquid crystal, which then transforms into a solid state (this process can occur by evaporation of the solvent resulting in an increase in concentration), thereby producing the films 2000a, 2000b with an ordered self-assembled microstructure that can refract light to produce structural color. This self-assembly can be adjusted and is driven by the balance between attractive van der Waals forces and repulsive interactions, which can be controlled in various ways, such as the charge of the particles, the ionic strength, etc.

[0307] In some instances, the self-assembled microstructure of the anisotropic organic nanocrystals can be made to exhibit disorder in the relative arrangement of the anisotropic organic nanocrystals, for example, by adjusting the self-assembly to produce tilted domains, ill-defined domains, small domains, large variations in the pitch of the structure, etc. This can be achieved by reducing the overall alignment of the anisotropic nanocrystals on the films 2000a, 2000b, which must occur after the suspension reaches the critical concentration (usually about 4 - 8 wt%) during the drying process but before the kinetics stop (about 6 - 10 wt%). In the case of domain alignment, the self-assembled microstructure can have parallel cholesteric axes across the films 2000a, 2000b, but such overall alignment may not be achieved, resulting in domains with different cholesteric axis angles. Such structures can be observed by polarized light microscopy and / or scanning electron microscopy (SEM). Such less ordered (even disordered) microstructures can provide different optical effects, such as a wider viewing angle, a pixelated flash effect (describing small spots of different colors), the range of colors produced, etc.

[0308] Additive

[0309] The membranes 2000a, 2000b are not required and typically are not formed solely from the self-assembled microstructure of anisotropic nanocrystals. The suspension 2003 may contain various types of additives for incorporation into the microstructure to modify its properties - subject to the volume / weight fraction limitations described above. The additives described below and additional additives may be included in any combination.

[0310] The self-assembled microstructure of anisotropic nanocrystals may include one or more pigments. These pigments may be added as separate additives to the suspension 2003, which can be simply incorporated into / around the self-assembled microstructure. Alternatively, the pigments may be directly included within the anisotropic nanocrystals.

[0311] The membranes 2000a, 2000b (or the suspension 2003 used to form the membranes) may contain a mixture or blend of two or more pigments. The pigments may be inorganic or organic.

[0312] The membranes 2000a, 2000b may have a color that is partly due to the structural color of the self-assembled microstructure of anisotropic nanocrystals and partly due to any pigments included.

[0313] Alternatively, when the self-assembled microstructure of anisotropic nanocrystals does not exhibit a structural color, the coloring of such membranes 2000a, 2000b may be mainly determined by any pigments included (in combination with the underlying color of the anisotropic nanocrystals).

[0314] The suspension 2003 (and the resulting membranes 2000a, 2000b) may also include additives in the form of plasticizers. Such as sorbitol, glycerol, propylene glycol, polyethylene glycol, and organic esters. These additives can enhance the mechanical strength of the membranes 2000a, 2000b without disrupting the self-assembly of the nanocrystals.

[0315] The suspension 2003 (and the resulting membranes 2000a, 2000b) may also include additives in the form of cross-linking agents. For example, phytic acid.

[0316] The suspension 2003 (and the resulting membranes 2000a, 2000b) may also include additives in the form of high-contrast absorbers. Such as carbon black, graphite, graphene, graphene oxide, etc.

[0317] The suspension 2003 (and the resulting membranes 2000a, 2000b) may also include additives in the form of inorganic particles. For example, silicon.

[0318] The suspension 2003 (and the resulting films 2000a, 2000b) may also include additives in the form of oils and / or waxes. When included, the oils and / or waxes may be distributed within the self-assembled microstructure of the anisotropic nanocrystals. Additionally or alternatively, the oils and / or waxes may form or be applied as a coating on the films 2000a, 2000b after drying. In some instances, the oils and / or waxes may be encapsulated by another material or chamber. The oil may be synthetic or natural, such as vegetable oil, seed oil, silica-based oil, etc. The wax may be synthetic or natural, such as paraffin wax, rice bran wax, beeswax, carnauba wax, etc.

[0319] The suspension 2003 (and the resulting films 2000a, 2000b) may also include additives in the form of fibers. For example, the fibers may be cellulose fibers, and the anisotropic nanocrystals may be cellulose nanocrystals. For example, hemicellulose, cellulose fibers, cellulose nanofibers, cellulose fibrils, etc.

[0320] The suspension 2003 (and the resulting films 2000a, 2000b) may also include additives in the form of polymers, such as, for example, lignin latex, polyvinyl alcohol, hemicellulose, etc.

[0321] The polymer may act as a plasticizer or provide cross-linking between the anisotropic nanocrystals (i.e., the previously described plasticizer / cross-linker may be in the form of a polymer). Alternatively, the polymer may take the form of a matrix in which the anisotropic nanocrystals are embedded. The polymer may have the same monomer units as the anisotropic nanocrystals.

[0322] Through-hole

[0323] The films 2000a, 2000b (or examples thereof) may include one or more through-holes. The through-holes may be circular, square, rectangular, or any other regular or irregular shape. The through-holes are preferably formed integrally when forming the films 2000a, 2000b, rather than being cut, drilled, or punched after forming the films 2000a, 2000b.

[0324] A rod or similar protrusion may be used to form the through-holes in the same manner as described for the rod 107 in the example of the sequins formed from cellulose nanocrystals.

[0325] When using the template 15, a rod or similar protrusion may be used to form the through-holes. Alternatively, the through-holes may be formed, or at least the thinning region for generating the through-holes, by adding a non-wettable region 2018 completely surrounded by a wettable region 2016.

[0326] Materials for the membrane

[0327] Examples have been described with respect to the formation of films 2000a, 2000b using cellulose nanocrystals in aqueous suspension 2003. However, as discussed herein, the same physical and colloidal chemistry principles apply to a wider range of suspensions of anisotropic nanocrystals in a range of different solvents / solvent blends.

[0328] Preferably, the anisotropic nanocrystals are formed from biopolymers (such as, for example, chitin), cellulose nanocrystals (such as bacterial cellulose nanocrystals or neutralized cellulose nanocrystals), or a mixture where cellulose nanocrystals or chitin induce self-assembly and the other particles follow.

[0329] Articles including the membrane

[0330] The films 2000a, 2000b described herein can generally be separated from the mold 2001 or the template 2015 and then mechanically self-supported. Such films 2000a, 2000b are not supported on a substrate. In other words, the films 2000a 2000b can be independent.

[0331] However, some applications may require that the films 2000a, 2000b be incorporated into a larger article.

[0332] In a first example, the article (not shown) may include a film 2000a, 2000b supported on a substrate (not shown). The substrate may be a film, a sheet, a plate or even a surface of a three-dimensional object. In some instances, the substrate may be a second film 2000a, 2000b of the same type and / or material. The substrate may be a porous material, such as a closed cell or an open cell. The substrate may include a polymer, paper, card, fabric, fiber mat, one or more of the aforementioned types of laminates, etc. or may be formed by the material.

[0333] Such an article may be formed by drying the films 2000a, 2000b directly onto a substrate (not shown), for example by applying a non-wettable region 2018 to define the perimeter 2009. Alternatively, a wall 2006 formed of an elastomeric material such as silicone rubber may be adhered to or pressed against the substrate during dispensing and drying of the suspension 2003.

[0334] Alternatively, the free-standing membranes 2000a, 2000b can be adhered to the substrate using an adhesive, or depending on the material of the membranes 2000a, 2000b, they can be wetted with a solvent (e.g., the same as used in the suspension 2003). The wetted free-standing membranes 2000a, 2000b are then placed or pressed into contact with the substrate and allowed to dry. This can be achieved on different surface materials such as glass, wood, metal, textiles, etc. These surfaces can be non-flat surfaces. Wetting of the membranes 2000a, 2000b causes the structure to expand, allowing a small amount of movement of the anisotropic nanocrystals within the self-assembled microstructure, thus orienting them to the interface of the substrate to create adhesion.

[0335] In a second instance, an article (not shown) can include the membranes 2000a, 2000b adhered between a first layer (not shown) and a second layer. In other words, the second instance of the article forms a laminate. The first layer and the second layer can take any form described above for the substrate (not shown) of the first instance of the article. The first layer and the second layer can be formed of different materials.

[0336] In a third instance, an article (not shown) can include a coating (not shown) covering at least one surface of the membranes 2000a, 2000b. The coating can provide a barrier layer that protects the self-assembled microstructure of the anisotropic nanocrystals from moisture, chemicals (e.g., cleaning products / compositions) to which it may be exposed, etc. The coating can alter or enhance the mechanical properties of the membranes 2000a, 2000b, for example, by increasing rigidity, by filling cracks, etc. The surface of the membranes 2000a, 2000b that is not covered by the coating can be adhered to or supported on a substrate (not shown) as described above for the first instance of the article (not shown).

[0337] Optionally, the coating can encapsulate most of the surface of the membranes 2000a, 2000b, e.g., at least 90% of the surface, or even the entire surface of the membranes 2000a, 2000b.

[0338] Coating the membranes 2000a, 2000b can enable the article to achieve a wider range of properties and / or appearances. For example, a cellulose acetate coating can allow the production of waterproof sequins mainly formed by the cellulose nanocrystals that form the membranes 2000a, 2000b. In this way, a laminated article can be formed that has a structurally colored core (membranes 2000a, 2000b) and is surrounded by a protective coating, thus providing a combination of waterproofness, structural color, and mechanical strength.

[0339] In a fourth example, an article (not shown) can include membranes 2000a, 2000b embedded in a transparent material (not shown). For example, the membranes can be embedded in a transparent epoxy resin (not shown) and cast into a mold (not shown) where the membranes 2000a, 2000b (or a plurality of membranes) are pre-positioned to form the shape of a gemstone. This method can be used to produce beads / costume jewelry that benefit from the optical characteristics of the membranes 2000a, 2000b.

[0340] The membranes 2000a, 2000b described herein, or an article (not shown) including these membranes 2000a, 2000b, can be used to provide (but are not limited to) sequins, sequin rolls, sequin trims, sequin nets, glitter, jewels, gemstones, jewelry ornaments, costume jewelry ornaments, pendants, colored ornaments, earrings, buttons, stickers, flash chips, cubic zirconias, thermoset crystals, ornaments, beads, nail art, glass stickers, ornaments, confetti, labels, tokens, metallic foils, or any other type of object used or applied to provide specular reflection, sparkle, iridescence, or a similar effect to an object.

[0341] The membranes 2000a, 2000b described herein, or an article (not shown) including these membranes 2000a, 2000b, can be used to provide (but are not limited to) jigsaw puzzle pieces, coasters, poker chips, trading cards, game pieces, etc.

[0342] The membranes 2000a, 2000b described herein, or an article (not shown) including these membranes 2000a, 2000b, can be applied to a fabric or other surface by applying a suspension containing anisotropic nanocrystals using a screen printing process, dot matrix printing process, dot printing process, ultraviolet printing process, inkjet printing process, flexographic printing process, gravure printing process, lithographic printing process, etc.

[0343] The membranes 2000a, 2000b described herein, or an article (not shown) including these membranes 2000a, 2000b, can be used as an alternative to a foil layer for fabrics, papers, cards, etc.

[0344] The methods described herein can be used to produce membranes 2000a, 2000b having an elongated shape, such as, for example, a sequin roll on a roll (sometimes also referred to as a "sequin ribbon"), thereby maintaining the edge effect around most of the perimeter of each sequin forming the roll.

[0345] Experimental characterization of shape, microstructure and optical properties

[0346] Also refer to Figures 17A to 17D where SEM images are presented.

[0347] Each SEM image obtained shows a cross-section of the first type of film 2000a at its periphery 2009. The film 2000a was broken (bent and fractured) in the middle to image the cross-section of the film 2000a.

[0348] Figures 17A to 17D All show that the film 2000a itself bends backward to form a back-bent portion 2013. It can be observed that when the film 2000a itself bends backward, the pseudo-layers in the microstructure remain continuous. The sample was sputter-coated with 7 nm of carbon. The images were taken using a Zeiss Gemini ultra plus.

[0349] With particular reference to Figure 17A , the observed edge effects generally correspond to the Figure 11 , 13A and the combination shown in 13F.

[0350] With particular reference to Figure 17B , the observed edge effects generally correspond to the Figure 13G combination shown in.

[0351] With particular reference to Figure 17C , the observed edge effects generally correspond to the Figure 13C and 13D combination shown in.

[0352] With particular reference to Figure 17D , the observed edge effects generally correspond to the Figure 11 , 13A and the combination shown in 13F.

[0353] Also refer to Figure 18 , which shows optical microscopy of the cellulose nanocrystal film 2000a in the form of glitter from a series of observation angles.

[0354] It can be observed that the color and intensity of the structural color produced by the self-assembled cellulose nanocrystal microstructure exhibit angular dependence. The images were taken using a Keyence(RTM) VHX-7000N instrument.

[0355] Also refer to Figure 19 , which presents a Figure 18 3D optical image of the cellulose nanocrystal glitter shown in.

[0356] Edge effects (back-bent portion 2013) can be observed around the periphery 2009. The height hr of the back-bent portion 2013 is approximately twice the thickness of the film at the centroid. Figure 19 The data were obtained using a Keyence(RTM) VHX-7000N instrument.

[0357] Also refer toFigure 20A and 20B , showing a photograph of the second type of film 2000b. Figure 20A In an approximately planar orientation. Figure 20B Shows a Figure 20A side view of a fractured cross-section of the film 2000b shown in

[0358] The illustrated film 2000b is made to have a curved edge around the perimeter 2009, the minimum radius of curvature r min being approximately one quarter of the thickness of the centroid 2008. The illustrated film 2000b is produced on a hydrophobic substrate of silicone rubber (as template 2015), thus forming a curved smooth edge, rather than the bent-back portion 2013 of the first type of film 2000a.

[0359] Also refer to Figure 21 , showing a scanning electron microscope (SEM) cross-sectional image of a comparative example thin film.

[0360] The comparative example thin film is produced using the same cellulose nanocrystal suspension 2003 as the Figures 17A to 17D film 2000a shown in

[0361] In Figure 21 , fracture at the edge of the comparative example thin film can be observed, corresponding to the point where the comparative example thin film meets the edge of the petri dish. It can be observed that the pseudo-layers remain well-aligned and the angle of the cholesteric axis with respect to the body of the comparative example thin film does not change compared to the edge, resulting in a weak point (fracture) at this edge.

[0362] Without being bound by theory, it is believed that this is due to anchoring to the dominant domains of the petri dish and cholesteric axis alignment. When anchoring to the petri dish is dominant, this is thought to produce an edge effect where the helical axis changes abruptly, resulting in fracture and leaving a sharp edge. This sharp edge is brittle and exposed, leading to further fracture, tearing, and / or snagging of other materials.

[0363] Compared to the comparative example thin film shown in Figure 21 , also refer to Figure 22 , showing a scanning electron microscope image of an example of the second type of film 2000b.

[0364] It can be observed that Figure 22Examples of the second type of membrane 2000b, as shown, exhibit smooth, non-sharp edges and retain a significant portion (greater than 0.1 times) of the thickness at the centroid within the minimum radius of curvature. Prior to SEM imaging, the second type of membrane 2000b was sputter-coated with 10 nm of carbon.

[0365] Once fully dried, the membranes 2000a, 2000b can be post-treated by heat treatment. The heat treatment can apply pressure or no pressure to the membranes 2000a, 2000b.

[0366] Once fully dried, the membranes 2000a, 2000b can be post-treated by alkali treatment. The alkali treatment can apply heat or no heat to the membranes 2000a, 2000b.

[0367] These membranes can be attached to different substrates in a variety of ways, including sewing onto textiles to form sequined fabrics, which can be used in a variety of different industries and use cases.

[0368] From the above discussion, it can be understood that the embodiments shown in the drawings are merely exemplary and include features that can be generalized, removed, or replaced as described herein and as stated in the claims. In the context of the present disclosure, other examples and variations of the devices and methods described herein will be apparent to those skilled in the art.

Claims

1. A film formed from a self-assembled microstructure of anisotropic nanocrystals and having a centroid and a perimeter, wherein around most of the perimeter, the film itself bends backward.

2. A membrane formed from a self-assembled microstructure of anisotropic nanocrystals and having an upper surface, a lower surface, a centroid, and a perimeter, wherein, Moving from the upper surface to the lower surface around any point on the perimeter, the minimum radius of curvature is at least 0.1 times the thickness of the film at the centroid.

3. The film according to claim 1 or 2, wherein the anisotropic nanocrystals account for at least 70% by volume fraction of the self-assembled microstructure.

4. The film according to any one of claims 1 to 3, wherein the film is formed as a single piece by drying a suspension comprising the anisotropic nanocrystals.

5. The film according to any one of claims 1 to 4, wherein the self-assembled microstructure of the anisotropic nanocrystals exhibits structural color.

6. The film according to any one of claims 1 to 5, wherein the self-assembled microstructure of the anisotropic nanocrystals comprises one or more pigments.

7. The film according to any one of claims 1 to 6, wherein the self-assembled microstructure of the anisotropic nanocrystals comprises one or more additives.

8. The film according to claim 7, wherein the one or more additives comprise at least one type of inorganic particles.

9. The film according to claim 7 or 8, wherein the one or more additives comprise fibers.

10. The film according to any one of claims 7 to 9, wherein the one or more additives comprise at least one polymer.

11. The film according to any one of claims 1 to 10, wherein the film is mechanically self-supporting.

12. The film according to any one of claims 1 to 11, further comprising one or more through-holes.

13. The film according to any one of claims 1 to 12, wherein the self-assembled microstructure of the anisotropic nanocrystals reflects light of a target wavelength.

14. The film according to any one of claims 1 to 13, wherein the anisotropic nanocrystals are formed from a biopolymer.

15. The film according to claim 14, wherein the anisotropic nanocrystals are cellulose nanocrystals.

16. An article comprising the film according to any one of claims 1 to 15 supported on a substrate.

17. An article comprising the film according to any one of claims 1 to 15 adhered between a first layer and a second layer.

18. An article comprising the film according to any one of claims 1 to 15, further comprising a coating covering at least one surface of the film.

19. The article according to claim 18, wherein the coating encapsulates most of the surface of the film.

20. An article comprising the film according to any one of claims 1 to 15 embedded in a transparent material.

21. A method of forming a film, comprising: Dispensing a volume of suspension into a mold or a template, the suspension comprising a suspension of anisotropic nanocrystals in a solvent; And Drying the dispensed suspension to form a film having a self-assembled microstructure of the anisotropic nanocrystals and having a centroid and a perimeter, wherein around most of the perimeter, the film itself bends backward.

22. A method of forming a film, comprising: Dispensing a volume of a suspension into a mold or a template, the suspension comprising a suspension of anisotropic nanocrystals in a solvent; And Drying the dispensed suspension to form a self-assembled microstructure having the anisotropic nanocrystals and a film having an upper surface, a lower surface, a centroid, and a perimeter, wherein moving from the upper surface to the lower surface around any point on the perimeter, the minimum radius of curvature is at least 0.1 times the thickness of the film at the centroid.

23. The method according to claim 21 or 22, wherein the volume of the suspension is dispensed into a mold having a wall height less than or equal to 3 mm; wherein the volume of the dispensed suspension is greater than the volume that can be accommodated up to the wall height of the mold.

24. The method according to claim 21 or 22, wherein the volume of the suspension is dispensed into a mold or a template formed by embossing a first substrate either convexly or concavely.

25. The method according to claim 21 or 22, wherein the volume of the suspension is dispensed into a template comprising a first region of a second substrate, the suspension wetting the first region, the first region being surrounded and defined by a second region that the suspension does not wet.

26. The method according to any one of claims 21 to 25, wherein the suspension comprises one or more pigments.

27. The method according to any one of claims 21 to 26, wherein the suspension comprises one or more additives.

28. The method according to claim 27, wherein the one or more additives comprise at least one type of inorganic particles.

29. The film according to claim 27 or 28, wherein the one or more additives comprise fibers.

30. The film according to any one of claims 27 to 29, wherein the one or more additives comprise at least one polymer.

31. The method according to any one of claims 27 to 30, wherein the one or more additives comprise two or more polymer precursors that react in the suspension to form a polymer.

32. The method according to any one of claims 21 to 31, wherein the mold or the template further comprises one or more through-hole structures, the through-hole structures being arranged such that the resulting film comprises through-holes corresponding to each through-hole structure.

33. The method according to any one of claims 21 to 32, wherein the anisotropic nanocrystals are formed of a biopolymer.

34. The film according to claim 33, wherein the anisotropic nanocrystals are cellulose nanocrystals.

35. The method according to any one of claims 21 to 34, wherein the suspension is an aqueous suspension comprising 2 wt% cellulose nanocrystals.

36. The method according to any one of claims 21 to 35, wherein during the drying of the suspension, the temperature is maintained between 18 °C and 25 °C.

37. The method according to any one of claims 21 to 36, wherein during the drying of the suspension, the humidity is maintained between 48% and 65%.

38. The method according to any one of claims 21 to 37, further comprising subjecting the dispensed suspension to a constant, uniform air flow.

39. The method according to any one of claims 21 to 38, wherein the film is detachable from the mold or template.

40. The method according to any one of claims 21 to 38, wherein the film is dried and remains adhered to the third substrate.

41. A method comprising: wetting the film according to any one of claims 1 to 15 with a second solvent; bringing the film into contact with the surface of an object; drying the second solvent such that the film becomes adhered to the surface of the object.

42. A method of manufacturing iridescent biodegradable sequins, the method comprising: obtaining a suspension of cellulose nanocrystals and a plasticizer dissolved in water; dispensing the suspension into a flexible mold; drying the dispensed suspension at a temperature between 18 °C and 25 °C and a relative humidity between 48% and 65% to produce dried iridescent sequins; bending the mold to detach the dried iridescent biodegradable sequins from the mold.

43. The method according to claim 42, wherein the mold comprises a plurality of containers for receiving the suspension, and wherein each container comprises an upright rod made of the same material as the rest of the mold for creating holes in the sequins upon drying.

44. The method according to claim 3, wherein the suspension is dispensed into each of the containers of the mold adjacent to the rod.

45. The method according to any one of claims 42 to 44, wherein the suspension is a 2 wt% suspension of cellulose nanocrystals.

46. The method according to any one of claims 42 to 45, wherein the plasticizer comprises sorbitol.

47. The method according to any one of claims 42 to 46, wherein the ratio of the plasticizer is 10 wt% of the dry mass of the cellulose nanocrystals.

48. The method according to any one of claims 42 to 47, wherein the suspension further comprises a crosslinking agent.

49. The method according to any one of claims 42 to 48, wherein the suspension further comprises a colored dye.

50. The method according to claim 43 or any of its dependent claims, wherein each of the containers is circular.

51. The method according to claim 43 or any of its dependent claims, wherein each container has a diameter of 10 mm, a wall height or depth of 0.3 - 0.5 mm, wherein the rod has a diameter of 1.2 mm, is 3 mm from the edge, and 3 mm from the center.

52. The method according to claim 51, wherein 200 microliters of solution is dispensed into each container.

53. The method according to any one of claims 42 to 52, wherein the temperature is preferably 23 °C.

54. The method according to any one of claims 42 to 53, wherein the humidity is preferably 50%.

55. The method according to any one of claims 42 to 54, further comprising the step of coating the iridescent sequins in a cellulose material.

56. The method according to any one of claims 42 to 55, wherein drying the dispensed suspension comprises subjecting the dispensed suspension to a constant, uniform air flow.

57. A rainbow glitter which is made according to the method of any one of claims 42 to 56.

58. A rainbow glitter which comprises cellulose nanocrystals and a plasticizer.

59. The rainbow glitter according to claim 58, wherein the plasticizer is sorbitol.

60. The rainbow glitter according to claim 58 or 59, wherein the ratio of the plasticizer is 10% of the dry mass of the cellulose nanocrystals.

61. The rainbow glitter according to any one of claims 57 to 60, which further comprises a crosslinking agent.

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