Sequins and methods for manufacturing sequins

Abstract

Films (2000a, 2000b) formed from self-assembled microstructures of anisotropic nanocrystals are described. The films (2000a, 2000b) have an upper surface (2011), a lower surface (2010), a center of gravity (2008), and a periphery (2009). In a first type of film (2000a), the film (2000a) curls back on itself (2013) around a majority of the periphery (2009). A second type of film (2000b) is shaped such that the minimum radius of curvature (rmin) around any point on the periphery (2009) moving from the upper surface (2011) to the lower surface (2010) is at least 0.1 times the thickness of the film (2000b) at the center of gravity (2008).

Description

[Technical Field]

[0001] The present disclosure relates to films formed from self-assembled microstructures of anisotropic nanocrystals, articles including such films, and methods of forming the films and articles. Among other uses, the films may be used to provide sequins or bio-iridescent sequins and methods of making such sequins, examples of which include biodegradable sequins made from cellulosic materials, examples of which include cellulose nanocrystals (CNCs). [Background technology]

[0002] Embroidery is the art of decorating textiles with additional materials to enhance the final garment. The most commonly applied materials are in the form of beads, sequins, thread, gemstones, and crystals. Through design and various application techniques, these materials can transform textiles, enhance their aesthetic, tactile, or functional qualities, and / or add cultural significance and purpose.

[0003] Sequins (or "paillettes" or "sequins") are small decorative, sparkling disks of various shapes and sizes, often sewn in large numbers onto clothing to create a shimmering effect. Originally, these disks were made of metal and served as powerful cultural symbols.

[0004] However, advances in technology, industrial mining, and machinery mean that sequins are now commonly made from low-cost plastics.

[0005] The essence of sequins is their sparkle. What was once a desirable quality available only to those of high social status has now become a mass-consumable commodity due to the low cost and easily moldable properties of modern plastics. Sparkle can be imitated by using coatings in a variety of shimmering colors made from petroleum and similar chemical mixtures.

[0006] The most widely used sequins are primarily made from PVC (polyvinyl chloride) or PET (polyethylene terephthalate). These plastics are chemical polymers derived from petroleum. They come in a variety of surface finishes, including matte, silk, two-tone, pearl, mirror, metallic, and iridescent.

[0007] In 2017, the Ellen MacArthur Foundation® published a research report, “A New Textiles Economy: Redesigning Fashion’s Future,” which raised troubling questions about the textile industry’s use of petrochemicals and the release of microplastics into the environment.

[0008] Reports from the past decade state that "PVC's life cycle (production, use, and disposal) results in the release of toxic chlorinated chemicals. These toxins accumulate in water, air, and the food chain, causing serious health problems, including cancer, immune system damage, and hormone disruption." (Greenpeace®) Given the size of some types of sequins (which can be less than 5mm in diameter), they fall into the microplastic category, along with microbeads found in cosmetics and glitter. "Microplastics are very small pieces of plastic. Size definitions vary across studies, but are most commonly defined as up to 5 millimeters." (Ellen MacArthur Foundation®) "Research has shown that small plastic particles have adverse effects primarily due to their digestion by aquatic organisms throughout the food chain. Ingestion of microplastics has been demonstrated to cause starvation and stunted growth in some species, and they have the ability to break down in the digestive system and release substances of concern." (Ellen MacArthur Foundation®) "Urban contamination of the oceans by microplastics is becoming a major concern, without a clear understanding of the long-term effects. Given the scale of this global marine pollution, some have referred to the current human period as the "Plasticine" rather than the "Anthropocene," and described the world's oceans as a "plastic soup."

[0009] Current attempts to create more sustainable sequins include the limited creation of cellulose sequins by Langlois-Martin Products (https: / / www.pailletteslangloismartin.fr / en / home-page / ), as well as sequins made from food waste (http: / / www.alicepotts.com / bioplastic.html and https: / / cqstudio.uk / materialsprojects / excessories-c534m). Langlois-Martin creates sequins from cellulose acetate, which is made by transforming cotton or wood fibers (80% of the composition) with a solvent (20%), which primarily evaporates during processing. The Sustainable Sequin Company also produces sequins from recycled polyester and is pursuing the creation of sequins from compostable bioplastics (https: / / futurefashionfactory.org / a-new-solution-for-sustainable-sequins / ).

[0010] Through a series of experiments, Meert et al., 'Taking a shine to it: How the preference for glossy stems from an innate need for water' (JCP 2014) from Ghent University in Belgium, concluded that "the preference for shiny and sparkling objects stems from an innate need for water resources." The desire for shiny and vibrant color effects is deeply rooted in human instincts, making them an essential component of countless industrial products (packaging, cosmetics, textiles, coatings, automotive). These shiny materials come in many forms beyond sequins, including components, glitter, confetti, pigments, paints, inks, coatings, foils, and sheets. To continue providing consumers with colorful effects while complying with the United Nations Sustainable Development Goals and new environmental policies, industries need sustainably sourced, circular, biodegradable, and recyclable alternatives to plastics and metals.

[0011] US 5,629,055 A describes solid films with novel optical properties produced from colloidal suspensions of cellulose microcrystals.

[0012] Cellulose nanocrystals are rod-shaped nanoparticles extracted from cellulose. Dispersing cellulose nanoparticles in water can lead to the formation of chiral nematic liquid crystals, and these structures can be preserved in the solid state. This nanoarchitecture or microstructure can reflect light in the visible spectrum, producing structural colors.

[0013] Zhao et al., "Printing of Responsive Photonic Cellulose Nanocrystal Microfilm Arrays," Adv. Funct. Mater. 2018, describes a study on producing coatings using cellulose nanocrystals by a blade coating technique. SEM of the edges described by Zhao et al. shows a gradual decrease in thickness towards the edge of the film. However, in highly ordered films, the cholesteric axis remains perpendicular to the substrate, and therefore the edge effect observed by Zhao et al. results in a decrease in the intensity of the structural color observed compared to the decrease in thickness approaching the periphery. Summary of the Invention

[0014] Aspects of the invention are set out in independent claims, with optional features set out in dependent claims. Aspects of the invention may be provided in conjunction with each other and features of one aspect may be applied to other aspects.

[0015] According to a first aspect of the present invention, there is provided a membrane formed from a self-assembled microstructure of anisotropic nanocrystals, the membrane having a center of gravity and a perimeter, the membrane curling back upon itself around a majority of the perimeter.

[0016] The perimeter may correspond to the contour of the projection of the membrane onto a plane perpendicular to the thickness of the membrane at the center of gravity.

[0017] The membrane does not enclose a volume. The membrane may be curled back upon itself in a cross-sectional plane parallel to the thickness of the membrane at corresponding points on the periphery. The membrane may be curled back upon itself by a distance equal to at least 0.1 times the thickness of the membrane at the center of gravity. The membrane may be curled back upon itself by a distance equal to at least 0.2 times the thickness of the membrane at the center of gravity. The membrane may be curled back upon itself by a distance equal to at least 0.5 times the thickness of the membrane at the center of gravity.

[0018] In this way, sharp or thin edges may be avoided at the perimeter. As a result, crack initiation / propagation may be suppressed at the perimeter (which may correspond to the maximum stress in many loading scenarios). This edge effect creates a film that may be less susceptible to fracture or cracking than previous films formed from anisotropic nanocrystalline self-assembled microstructures. However, the warped (or "recurved") portion may still end up with sharp / thin edges.

[0019] The membrane of the first aspect may include features corresponding to any features of the method of the sixth aspect. Definitions applicable to the method of the sixth aspect (or features thereof) may be equally applicable to the membrane of the first aspect (or features thereof).

[0020] According to a second aspect of the present invention, there is provided a film formed from a self-assembled microstructure of anisotropic nanocrystals, the film having an upper surface, a lower surface, a center of gravity and a perimeter, wherein the smallest radius of curvature when moving from the upper surface to the lower surface around any point on the perimeter is at least 0.1 times the thickness of the film at the center of gravity.

[0021] The perimeter may correspond to the contour of the projection of the membrane onto a plane perpendicular to the thickness of the membrane at the center of gravity.

[0022] As with the first embodiment membrane, the second embodiment membrane may avoid sharp or thin edges at the periphery. As a result, crack initiation / propagation may be suppressed at the periphery (which may correspond to maximum stress in many loading scenarios). This edge effect creates a membrane that may be less susceptible to fracture or cracking than previous membranes formed from self-assembled microstructures of anisotropic nanocrystals.

[0023] The membrane of the second aspect may include features corresponding to any features of the method of the sixth aspect. Definitions applicable to the method of the sixth aspect (or features thereof) may be equally applicable to the membrane of the second aspect (or features thereof).

[0024] The following optional features are equally applicable to the membrane of the first embodiment and / or the membrane of the second embodiment (and / or articles containing either membrane).

[0025] The anisotropic nanocrystals may comprise a volume fraction of at least 70 wt% of the self-assembled microstructure. The anisotropic nanocrystals may comprise a volume fraction of at least 80 wt% of the self-assembled microstructure. The anisotropic nanocrystals may comprise a volume fraction of at least 90 wt% of the self-assembled microstructure. The anisotropic nanocrystals may be uniformly distributed throughout the volume of the film.

[0026] The film may be integrally formed by drying a suspension containing anisotropic nanocrystals. The origin of the film formed integrally by drying a suspension containing anisotropic nanocrystals may be determined by examining the directional alignment of the anisotropic nanocrystals. Such directional alignment may be determined by several means, examples of which include, but are not limited to, the following: Microscopic examination of fractured surfaces Microscopic examination of a cross section (e.g. polished), or · By inspecting the film using visible light between crossed polarizers, if the film is at least partially transparent.

[0027] If the edge effects on the directional alignment of the anisotropic nanocrystals are substantially similar from any point on the periphery toward the center of gravity, then the film is formed integrally by drying a suspension containing the anisotropic nanocrystals. If this is not the case, then this indicates that the film was cut from a larger object (thus eliminating some edge effect regions).

[0028] The membrane may be formed by drying in a mold. The mold may be flexible, for example, made of silicone rubber. The mold may be rigid. The mold may be formed by embossing a surface. The mold may be formed by debossing a surface. Alternatively, the membrane may be formed on a 2D mold in the form of a flat surface having areas that can be wetted by the suspension (defined by surrounding areas that cannot be wetted by the suspension). For example, if the suspension is aqueous, the 2D mold may include hydrophilic regions surrounded by hydrophobic regions that define the perimeter of the membrane, onto which the suspension is applied to form the membrane upon drying.

[0029] The self-assembled microstructure of anisotropic nanocrystals may exhibit structural color.

[0030] The self-assembled microstructure of anisotropic organic nanocrystals may have a pitch in the visible wavelength range (approximately 400-700 nm) and may exhibit structural color. The self-assembled microstructure of anisotropic organic nanocrystals may have a pitch in the near-infrared and infrared wavelengths (approximately 700-1000 nm) and reflect light at these wavelengths. The self-assembled microstructure of anisotropic organic nanocrystals may have a pitch in the UV and near-UV wavelength ranges and infrared and reflect back light at these wavelengths.

[0031] The self-assembled microstructure of the anisotropic nanocrystals may include one or more pigments. As used herein, the term pigment also includes dyes. The film may include a mixture or blend of two or more pigments. The pigments may be inorganic or organic. The film may have a color tone that is partially generated by the structural color from the self-assembled microstructure of the anisotropic nanocrystals and partially generated by one or more pigments. Any or all of the pigments may be included in the anisotropic nanocrystals. Any or all of the pigments may be external to the anisotropic nanocrystals, for example, in an additive component.

[0032] Alternatively, if the film contains one or more pigments, the self-assembled microstructure of anisotropic nanocrystals may not exhibit structural color.

[0033] The self-assembled microstructure of anisotropic nanocrystals may include one or more additives. The one or more additives may include a plasticizer. The one or more additives may include sorbitol, preferably sorbitol. The one or more additives may include a cross-linking agent. The additives may include a high contrast absorber, examples of which include, for example, carbon black, graphite, graphene, or graphene oxide.

[0034] The one or more additives may include an oil. The one or more additives may include a wax. The oil or wax may be dispersed within the self-assembled microstructure of the anisotropic nanocrystals. The oil or wax may form or be applied as a coating of a film. The oil or wax may be encapsulated by other materials or cells. The oil may be synthetic or natural, examples of which include vegetable oils, seed oils, silica-based oils, etc. The wax may be synthetic or natural, examples of which include paraffin, rice wax, beeswax, carnauba wax, etc.

[0035] The one or more additives may include at least one type of inorganic particle.

[0036] The one or more additives may include fibers, which may be cellulose fibers, and the anisotropic nanocrystals may be cellulose nanocrystals.

[0037] The one or more additives may include at least one polymer. The polymer may be a biopolymer. The polymer may function as a plasticizer. The polymer may function to provide cross-links 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 unit(s) as the anisotropic nanocrystals.

[0038] The membrane may be mechanically free-standing. The membrane may not be supported on a substrate. In other words, the membrane may stand free-standing.

[0039] 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 integrally formed during the formation of the membrane, rather than being cut, drilled, or stamped after the membrane is formed.

[0040] The self-assembled microstructure of anisotropic nanocrystals may reflect light at a target wavelength. The properties and distribution of the anisotropic nanocrystals and the formation of the self-assembled microstructure may be controlled to result in spacing of the anisotropic nanocrystals that couples light at the target wavelength by diffraction. The target wavelength may be in the visible wavelength range. The target wavelength may be in the infrared wavelength range. The target wavelength may be in the UV wavelength range.

[0041] The anisotropic nanocrystals may be organic. The anisotropic nanocrystals may be inorganic.

[0042] The anisotropic nanocrystals may be formed from biopolymers. The membrane may be biodegradable. The anisotropic nanocrystals may be biodegradable. The membrane may be compostable. The membrane may be recyclable.

[0043] 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 aforementioned materials.

[0044] The membrane may have a 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.

[0045] The membrane may be generally planar or film-like. The membrane may have the shape of a film that conforms to the surface of a three-dimensional shape, such as formed by drying a suspension of anisotropic nanocrystals in a correspondingly shaped mold.

[0046] The article may comprise the membrane of the first or second embodiment supported on a substrate. The substrate may be a 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 membrane of the same type. The substrate may be a porous material. The pores may be closed-cell. The pores may be open-cell.

[0047] The substrate may comprise or be formed from a polymer, examples of which include polylactic acid, alginate, polycaprolactone, cellulose acetate, and other biopolymers. The substrate may comprise or take the form of paper or card. The substrate may comprise or take the form of a fabric. The fabric may be synthetic, natural, nonwoven, or woven, examples of which include cotton, linen, hemp, viscose, lyocell, modal, silk, leather, chiffon, rayon, elastane, nylon, and blended fabrics. The substrate may comprise or take the form of a fiber mat. The substrate may comprise or take the form of a laminate. The substrate may comprise or take the form of a metal. The substrate may comprise or take the form of glass.

[0048] The article may include a film of the first or second embodiment 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 form previously described herein in relation to the substrate. The second layer may be in any form previously described herein in relation to the substrate. The first and second layers may be formed of the same material. The first and second layers may be formed of different materials.

[0049] The article may include a film of the first or second embodiment, and may also include a coating covering at least one surface of the film. The coating may provide a barrier layer that protects the self-assembled microstructure of anisotropic nanocrystals from moisture and / or other environmental factors. The coating may modify or enhance the mechanical properties of the film, for example, by increasing stiffness, filling cracks, etc. The surface of the film not covered by the coating may be bonded to or supported by a substrate as previously described herein.

[0050] The coating may encompass a majority of the surface of the membrane. The coating may encompass at least 90% of the surface of the membrane. The coating may encompass the entire surface of the membrane.

[0051] The article may comprise the film of the first or second embodiment embedded in a transparent material, for example the film may be embedded in a transparent epoxy.

[0052] The film or article comprising the film according to the first and / or second aspect may be used to provide, but is not limited to, sequins, glitter, jewels, gems, jewelry, costume jewelry, pendants, color pieces, ear pendants, buttons, stickers, sequins, rhinestones, hot fix crystals, ornaments, beads, nail art, glass stickers, decorative coatings, confetti, tags, tokens, tinsils or any other type of object that is used or adapted to provide a specular reflection, sparkle, metallic color, shimmering color, metallic shine pearlescent, holographic, iridescent or similar effect to an object.

[0053] The membranes according to the first and / or second aspects, or articles comprising the membranes, may also be used to provide, but are not limited to, puzzle pieces, coasters, poker chips, trading cards, game pieces, and the like.

[0054] The film according to the first and / or second aspect, or an article comprising the film, may be applied to a fabric or other surface by spreading a suspension comprising the 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.

[0055] The membrane according to the first and / or second aspect, or an article comprising the membrane, may be used as a foil replacement in fabrics, paper, cards and the like.

[0056] According to a third aspect of the present invention, there is provided a method of forming a membrane comprising dispensing a volume of a suspension into a mold or onto a template, the suspension comprising a suspension of anisotropic nanocrystals in a solvent, and drying the dispensed suspension to form a membrane having a self-assembled microstructure of the anisotropic nanocrystals and having a center of gravity and a perimeter, wherein the membrane curls back upon itself around a majority of the perimeter.

[0057] The method of the third aspect may include features corresponding to any feature of the membrane of the first and / or second aspect, or article containing said membrane(s). Definitions applicable to the membrane of the first and / or second aspect (or features thereof) may be equally applicable to the method of the third aspect (or features thereof).

[0058] The method of the third aspect may include features corresponding to any features of the method of the sixth aspect. Definitions applicable to the method of the sixth aspect (or features thereof) may be equally applicable to the method of the third aspect (or features thereof).

[0059] According to a fourth aspect of the present invention, there is provided a method of forming a membrane comprising dispensing a volume of a suspension into a mold or onto a template. The suspension comprises a suspension of anisotropic nanocrystals in a solvent. The method also includes drying the dispensed suspension to form a membrane having a self-assembled microstructure of the anisotropic nanocrystals and having an upper surface, a lower surface, a center of gravity, and a perimeter, wherein the smallest radius of curvature when moving from the upper surface to the lower surface around any point on the perimeter is at least 0.1 times the thickness of the membrane at the center of gravity.

[0060] The method of the fourth aspect may include features corresponding to any feature of the membrane of the first and / or second aspect, or of the article containing said membrane(s). Definitions applicable to the membrane of the first and / or second aspect (or features thereof) may be equally applicable to the method of the fourth aspect (or features thereof).

[0061] 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 of the sixth aspect (or features thereof) may be equally applicable to the method of the fourth aspect (or features thereof).

[0062] The following optional features are equally applicable to the method of the third and fourth aspects.

[0063] The method may include dispensing a volume into each of two or more molds arranged to form an array. All molds may be identical, but this is not essential. If the molds are not identical, different volumes of suspension may be dispensed, corresponding to each of molds of different types, shapes, or volumes.

[0064] The method may include dispensing a volume onto each of two or more templates arranged to form an array. All of the templates may be identical, but this is not essential. If the templates are not identical, different volumes of the suspension may be dispensed onto each of different types or shapes of templates.

[0065] The volume of suspension may be dispensed into a mold having walls with a height of 3 mm or less. The volume of suspension dispensed may be greater than the volume that would be contained up to the wall height of the mold. In other words, the mold may be filled to overflowing. Surface tension may prevent the dispensed volume from overflowing the mold, pinning and holding the suspension to the mold area.

[0066] The mold may be flexible. The mold may be made of silicone rubber. Alternatively, the mold may be rigid.

[0067] The mold may be formed of any material that has a surface energy that is compatible with the anisotropic nanocrystals such that the formation of the self-assembled microstructure is energetically favored at the air-suspension-mold interface (edge / 1D interface) compared to the suspension-mold interface (surface / 2D interface). The mold may be formed of any material that has poor adhesion to the self-assembled microstructure of the anisotropic nanocrystals, e.g., a contact angle of 50° or greater.

[0068] A volume of the suspension may be dispensed into a mold or template formed by embossing or debossing a first substrate.

[0069] The first substrate may be formed of any material that has a surface energy that is compatible with the anisotropic nanocrystals such that formation of the self-assembled microstructure is energetically favored at the air-suspension-second substrate interface (edge / 1D interface) compared to the suspension-second substrate interface (surface / 2D interface). The first substrate may be formed of any material that has poor adhesion to the self-assembled microstructure of the anisotropic nanocrystals, e.g., a contact angle of 50° or greater.

[0070] The first substrate may be a film. The first substrate may be a sheet. The first substrate may be a plate. The first substrate may be the surface of a three-dimensional object. The first substrate may be a second membrane of the same type. The first substrate may be a porous material. The pores may be closed-cell. The pores may be open-cell.

[0071] The first substrate may comprise or be formed from a polymer. The first substrate may comprise or be in the form of paper or card. The first substrate may comprise or be in the form of a fabric. The first substrate may comprise or be in the form of a fiber mat. The first substrate may comprise or be in the form of a laminate. The first substrate may comprise or be in the form of a metal. The substrate may comprise or be in the form of glass.

[0072] A volume of the suspension is dispensed onto a template including a first region of a second substrate that is wetted by the suspension, the first region being surrounded and possibly defined by a second region that is not wetted by the suspension.

[0073] A suspension may be considered to wet an area if the contact angle of a drop of suspension contacting the area is less than or equal to 90°. A suspension may be considered to not wet an area if the contact angle of a drop of suspension contacting the area is greater than 90°.

[0074] For example, if the suspension is aqueous, the 2D mold may include hydrophilic regions surrounded by hydrophobic regions that define the perimeter of the membrane, onto which the suspension is applied to form the membrane upon drying.

[0075] The second substrate may be formed of any material that has a surface energy that is compatible with the anisotropic nanocrystals such that the formation of the self-assembled microstructure is energetically favored at the air-suspension-second substrate interface (edge / 1D interface) compared to the suspension-second substrate interface (surface / 2D interface). The second substrate may be formed of any material that has poor adhesion to the self-assembled microstructure of the anisotropic nanocrystals, e.g., a contact angle of 50° or greater.

[0076] The second substrate may be a film. The second substrate may be a sheet. The second substrate may be a plate. The second substrate may be the surface of a three-dimensional object. The second substrate may be a second membrane of the same type. The second substrate may be a porous material. The pores may be closed-cell. The pores may be open-cell.

[0077] The second substrate may comprise or be formed from a polymer. The second substrate may comprise or be in the form of paper or card. The second substrate may comprise or be in the form of a fabric. The second substrate may comprise or be in the form of a fiber mat. The second substrate may comprise or be in the form of a laminate. The second substrate may comprise or be in the form of a metal. The substrate may comprise or be in the form of glass.

[0078] The suspension may include one or more pigments. The suspension may include a mixture or blend of two or more pigments. The pigments may be inorganic or organic. The resulting film may have a color that is partially generated by structural color from the self-assembled microstructure of the anisotropic nanocrystals and partially generated by one or more pigments. Any or all of the pigments may be included in the anisotropic nanocrystals. Any or all of the pigments may be external to the anisotropic nanocrystals, for example, in an additive component.

[0079] The suspension may include one or more additives. The one or more additives may include a plasticizer. The one or more additives may include sorbitol, preferably sorbitol. The one or more additives may include a cross-linking agent. The one or more additives may include a high contrast absorber, examples of which include, for example, carbon black or black algae, graphite, graphene, etc.

[0080] The one or more additives may include at least one type of inorganic particle.

[0081] The one or more additives may include an oil. The one or more additives may include a wax. The oil or wax may be dispersed within the self-assembled microstructure of the anisotropic nanocrystals. The oil or wax may form or be applied as a coating of a film. The oil or wax may be encapsulated by other materials or cells. The oil may be synthetic or natural, examples of which include vegetable oils, seed oils, silica-based oils, etc. The wax may be synthetic or natural, examples of which include paraffin, rice wax, beeswax, carnauba wax, etc.

[0082] The one or more additives may include fibers, which may be cellulose fibers, and the anisotropic nanocrystals may be cellulose nanocrystals.

[0083] The one or more additives may include at least one polymer. The polymer may function as a plasticizer. The polymer may function to provide cross-links 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 unit(s) as the anisotropic nanocrystals.

[0084] The one or more additives may include two or more polymer precursors that react in the suspension to form a polymer. One or more of the polymer precursors may be added to the suspension just before dispensing the suspension into a mold or onto a template. The polymer precursors may react to form the polymer in parallel with drying of the suspension.

[0085] The mold or template may also include one or more through-hole structures arranged so that the resulting membrane contains a through-hole 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.

[0086] The anisotropic nanocrystals may be formed from biopolymers.

[0087] The membrane may be biodegradable. The membrane may be compostable. The anisotropic nanocrystals may be biodegradable.

[0088] 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 aforementioned materials.

[0089] The suspension may be an aqueous suspension containing 2 wt% cellulose nanocrystals.

[0090] The temperature may be maintained between 18°C ​​and 25°C during drying of the suspension.

[0091] The humidity may be maintained between 48% and 65% during drying of the suspension.

[0092] The method may also include exposing the dispensed suspension to a constant, uniform air flow.

[0093] The method may also include exposing the dispensed suspension to a patterned or unpatterned electric field during drying. If the suspension exhibits liquid crystalline properties, the anisotropic nanocrystals may locally align with the electric field, resulting in a controllable pattern of structural color in the film.

[0094] The membrane may be releasable from the mold or template. The method may also include removing the dried membrane from the mold or template.

[0095] The membrane may be allowed to dry or may remain adhered to the third substrate. The third substrate may be received in the mold before dispensing the suspension. The template may include or take the form of the third substrate.

[0096] The third substrate may be a film. The third substrate may be a sheet. The third substrate may be a plate. The third substrate may be the surface of a three-dimensional object. The third substrate may be a second membrane of the same type. The third substrate may be a porous material. The pores may be closed-cell. The pores may be open-cell.

[0097] The third substrate may comprise or be formed from a polymer, examples of which include polylactic acid, alginate, polycaprolactone, cellulose acetate, and other biopolymers. The third substrate may comprise or be in the form of paper or card. The third substrate may comprise or be in the form of a fabric. The fabric may be synthetic, natural, nonwoven, or woven, examples of which include cotton, linen, hemp, viscose, lyocell, modal, silk, leather, chiffon, rayon, elastane, nylon, and blended fabrics. The third substrate may comprise or be in the form of a fiber mat. The substrate may comprise or be in the form of a laminate.

[0098] According to a fifth aspect of the present invention, there is provided a method comprising wetting a membrane according to the first or second aspect (and / or produced according to the method of the third or fourth aspect) using a second solvent. The method also comprises placing the membrane in contact with a surface of an object. The method also comprises drying the second solvent so that the membrane adheres to the surface of the object.

[0099] The second solvent may be the same solvent used in the suspension that was dried to form the membrane.

[0100] The method of the fifth aspect may include features corresponding to any features of the membrane of the first and / or second aspect, or of the article containing said membrane(s). Definitions applicable to the membrane of the first and / or second aspect (or features thereof) may be equally applicable to the method of the fifth aspect (or features thereof).

[0101] The method of the fifth aspect may include features corresponding to any features of the method of the third and / or fourth aspect. Definitions applicable to the method of the third and / or fourth aspect (or features thereof) may be equally applicable to the method of the fifth aspect (or features thereof).

[0102] The method of the fifth aspect may include features corresponding to any features of the method of the sixth aspect. Definitions applicable to the method of the sixth aspect (or features thereof) may be equally applicable to the method of the fifth aspect (or features thereof).

[0103] In contrast to traditional techniques for producing sequins, the sequins of the present disclosure are made using cellulose nanocrystals (CNCs), which create structural color due to the way the CNCs organize as they dry. This means that luster and color vibrancy can be achieved without the need for the use of pigments, minerals, or metals, resulting in a process that uses less resource-intensive materials.

[0104] Furthermore, it means that the sequins of the present disclosure may be biodegradable.

[0105] Additionally, while pigments may be added for color, they are not required to create iridescence. Eliminating the need to incorporate additional pigments is beneficial from both a formulation and cost perspective. Previously, decorative components made using cellulose acetate (or other bioplastics) required the addition of colorants and gloss agents. Additionally, working with CNC means that non-toxic solvents (such as water) may be used as the evaporation substrate, rather than toxic solvents.

[0106] Additionally, the sequins of the present disclosure may be made by casting them into a mold rather than punching them from sheet stock, which can potentially reduce waste (up to an average of 33%) because after the sequins are punched, perforated sheet stock (sometimes called punchinella) with no viable use remains.

[0107] Creating sequins by casting into a mold has an additional advantage: the precision mold imparts form / shape to the CNC material as it self-assembles (as the casting liquid dries), creating a fully formed shape / component that is less brittle than when cut or punched from sheet stock.

[0108] Accordingly, a sixth aspect of the present disclosure is a method for producing iridescent sequins (such as biodegradable sequins). The method includes obtaining a suspension of cellulose nanocrystals and a plasticizer in water, dispensing the suspension into a flexible mold, drying the dispensed suspension at a temperature of 18°C ​​to 25°C and a relative humidity of 48% to 65% to form a dried iridescent sequin, and flexing the mold to release the dried iridescent biodegradable sequin from the mold. Preferably, the drying time is at least 6 hours, and preferably at least 8 hours. At a temperature of 25°C, a 6-hour drying time is preferred.

[0109] It will be understood, however, that in some instances, a flexible mold may not be used. Thus, in such instances, the method would not include bending the mold to release the dried iridescent sequins from the mold. For example, the method may instead include some other technique for lifting the dried iridescent sequins from the mold. Examples include using suction / vacuum, possibly in combination with a mechanism for releasing an upright rod (see below); for example, the rod may be a separate item (such as a pin or nail extending through the mold) that may be removable from the mold, although it is generally preferred that the rod be the same material as the rest of the mold to avoid differences in surface tension that may result in undesirable structural properties (e.g., curvature) in the sequins upon drying.

[0110] Advantageously, when the sequins are fully formed as individual objects in a mold, they produce individual circular colors (bull's-eye or coffee ring effect, i.e., see, e.g., Klockars et al., Asymmetrical coffee rings from cellulose nanocrystals and prospects in art and design, Cellulose 26, 491-506 (2019)) that are natural to CNC self-assembly. This effect is unique in the field of sequin iridescence. Furthermore, this sequin formation method also allows for CNC color effects, such as solid or two-tone transitional colors. Furthermore, creating fully formed shapes avoids cutting from larger sheets and generating waste. In contrast to conventional sequins, the biodegradable sequins of the present disclosure have sustainable shine, luster, and vibrant colors that do not fade.

[0111] Preferably, the mold includes a plurality of receptacles for receiving the suspension, each receptacle including an upstanding rod for creating holes in the sequins upon drying, the rods being made from the same material as the rest of the mold, the rods being configured to pierce the sequins upon drying to enable the sequins to be sewn / embroidered onto garments or textiles.

[0112] In some examples, each receptacle is circular, although it will be appreciated that other geometric shapes, such as triangular or trapezoidal, may also be used.

[0113] Each receptacle may be circular, have a flat base, and have a diameter of 10 mm, with a wall height or depth of 0.3 to 0.5 mm. The rod diameter may be 0.8 to 1.5 mm, e.g., 0.8 to 1.2 mm, preferably 1.2 mm. Surprisingly, 1.2 mm has been found to be particularly effective in balancing the need to create holes in the sequins against the structural integrity of both the mold and the resulting sequins. In some examples, the rod is 3 mm from the edge and / or 2 mm from the center. With these dimensions, each receptacle is preferably dispensed with approximately 200 to 350 microliters of solution, preferably 250 to 330 microliters (preferably more solution than the volume of the receptacle is dispensed so that the solution forms a dome-shaped surface due to surface tension effects).

[0114] This ensures that, once the suspension dries, a flat sequin is formed with sufficient structural integrity. These dimensions have been found to produce a uniform film / sequin without raised edges and deformation around the rod / holes. However, it will be understood that sequins of other sizes may be produced. For sequins with other dimensions, the relative dimensions of the mold / receptacle components may remain the same. For example, even if the sequin diameter is reduced to 5 mm, the wall height or depth may remain 0.3-0.5 mm. Similarly, the rod may have the same 1.2 mm diameter, since thread must be threaded through the holes in the sequin to sew / embroider it onto a garment. However, the relative center-to-rod and wall-to-rod spacing may, of course, vary.

[0115] The suspension may be dispensed into each receptacle 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 sewing holes, avoiding punching holes and providing a circular rainbow pattern. Furthermore, dispensing the solution adjacent to the rod has also been found to reduce the likelihood of air bubbles forming in the solution (resulting in defective sequins).

[0116] The suspension may be a 2 wt% suspension of cellulose nanocrystals. The plasticizer may include, for example, sorbitol and / or glycerol. The plasticizer may be in a proportion of 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 color.

[0117] In some instances, the suspension further comprises a cross-linking agent.

[0118] In some instances, the suspension further comprises a color dye. The dye may be a food coloring, examples of which include Food Coloring Nos. 102 and 122 (2.3% total dye). The coloring was No. 122, a synthetic red coloring that belongs to the azo dye family, which is derived from coal tar and is mostly used in the confectionery industry, and No. 102, tartrazine, a synthetic lemon yellow azo dye primarily used as a food coloring. Synthetic colorings may also be used.

[0119] Preferably, 100% natural, plant-based natural food colorings may be used, such as a yellow coloring made from extract of real marigold petals (containing water, glycerin, and marigold extract (1.5%)), or a green coloring made from glycerin and spinach extract (18.7%).

[0120] The concentration is highly dependent on the dye used and its concentration relative to the water. Preferably, the concentration may range from about 0.6% to about 2.1% by volume. As a rough guide, two drops of dye (1 ml dye: 144 ml CNC) equals about 0.69%, four drops of dye (2 ml dye: 144 ml CNC) equals 1.39%, and six drops of dye (3 ml dye: 144 ml CNC) equals 2.07%. Using more than 10 drops (3.45%) can over-convert the CNC mixture, potentially affecting the organization of the CNCs as they dry to form the sequin.

[0121] The preferred drying temperature is 23°C. The preferred drying humidity is 50%. Surprisingly, it has been found that at these temperatures and humidity levels, the sequins dry at a rate slow enough to form aesthetically pleasing iridescent colors without drying the sequins too quickly and becoming too brittle.

[0122] In some examples, the method may further include coating the iridescent sequins with a cellulosic material (such as cellulose acetate).

[0123] Drying the dispensed suspension may include exposing the dispensed suspension to a constant, uniform flow of air, which may advantageously help ensure that all sequins within the 15 molds dry for the same time and rate.

[0124] In a seventh aspect of the present disclosure, there is a rainbow sequin made according to the method described above.

[0125] In an eighth aspect of the present disclosure, there is an iridescent sequin comprising cellulose nanocrystals and a plasticizer.

[0126] The plasticizer may be sorbitol, and may be present in a proportion of 10% of the dry mass of the cellulose nanocrystals.

[0127] The rainbow sequins may further include a cross-linking agent.

[0128] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0129] [Figure 1] 1 shows a perspective view of an exemplary mold for sequins including a dried sequin in each of a plurality of receptacles. [Figure 2A] 2 shows another schematic diagram of an exemplary mold for the sequins of FIG. 1 (without any sequins or suspension). [Figure 2B] 2B shows a cross-sectional view of an exemplary mold for the sequin of FIG. 2A. [Figure 2C] 2C shows an enlarged portion of the cross-sectional view of FIG. 2B. [Figure 2D] 1A-2C show schematic diagrams of receptacles of the type shown in FIGS. [Figure 3] 1 shows a perspective view of a robot dispensing suspension into each receptacle of a mold (such as the mold of FIG. 1 or FIG. 2). [Figure 4] 1 shows a photograph of an exemplary rainbow sequin produced in accordance with an embodiment of the present disclosure. [Figure 5] 1 shows an exemplary process flow diagram of an exemplary method for making rainbow sequins. [Figure 6] A plot of drying time and color intensity versus temperature is shown. [Figure 7] 1A-1C show a schematic representation of the formation of a membrane by dispensing a suspension of anisotropic nanocrystals into a mold. [Figure 8] 1A-1C show a schematic representation of the formation of a membrane by dispensing a suspension of anisotropic nanocrystals onto a mold. [Figure 9] 1A-1C show a schematic representation of film formation by dispensing a suspension of anisotropic nanocrystals into a mold formed by embossing a substrate. [Figure 10] 1A-1C show a schematic representation of film formation by dispensing a suspension of anisotropic nanocrystals into a mold formed by debossing a substrate. [Figure 11] 1 is a schematic cross-sectional view of a first type of membrane. [Figure 12] FIG. 2 is a schematic cross-sectional view of a second type of membrane. [Figure 13A] FIG. 2 is a schematic cross-sectional view of a first example of a first type of membrane. [Figure 13B] FIG. 2 is a schematic cross-sectional view of a second example of a first type of membrane. [Figure 13C] FIG. 10 is a schematic cross-sectional view of a third example of a first type of membrane. [Figure 13D] FIG. 10 is a schematic cross-sectional view of a fourth example of a first type of membrane. [Figure 13E] FIG. 10 is a schematic cross-sectional view of a fifth example of a first type of membrane. [Figure 13F] FIG. 10 is a schematic cross-sectional view of a sixth example of a first type of membrane. [Figure 13G] FIG. 10 is a schematic cross-sectional view of a seventh example of a first type of membrane. [Figure 14A] FIG. 2 is a schematic cross-sectional view of a first example of a second type of membrane. [Figure 14B] FIG. 1 is a schematic cross-sectional view of a second example of a second type of membrane. [Figure 14C] FIG. 10 is a schematic cross-sectional view of a third example of a second type of membrane. [Figure 14D] FIG. 10 is a schematic cross-sectional view of a fourth example of a second type of membrane. [Figure 14E] FIG. 10 is a schematic cross-sectional view of a fifth example of a second type of membrane. [Figure 14F] FIG. 10 is a schematic cross-sectional view of a sixth example of the second type of membrane. [Figure 15] 1 shows examples of the first type of film with various shapes between polarizers of different configurations. [Figure 16] A comparison of a membrane formed according to the present disclosure with a shape physically cut from a sheet having the same formulation under the same conditions as in FIG. 15 is shown. [Figure 17A] 1 shows a scanning electron microscope cross section of an example of a first type of membrane. [Figure 17B] 1 shows a scanning electron microscope cross section of an example of a first type of membrane. [Figure 17C] 1 shows a scanning electron microscope cross section of an example of a first type of membrane. [Figure 17D] 1 shows a scanning electron microscope cross section of an example of a first type of membrane. [Figure 18] 1 shows optical micrographs of the first type of cellulose nanocrystal film from a range of observation angles from 0° to 50°. [Figure 19] 19 is a 3D optical image of the cellulose nanocrystal film shown in FIG. 18. [Figure 20A] Photograph of a second type of cellulose nanocrystal film. [Figure 20B] 20B is a photograph showing the cross-sectional shape of the cellulose nanocrystal film shown in FIG. 20A broken in half. [Figure 21] 1 shows a scanning electron microscope cross section of a comparative example produced by drying a suspension of cellulose nanocrystals in a Petri dish. [Figure 22] 1 shows a scanning electron microscope cross section of a second type of cellulose nanocrystal film. DETAILED DESCRIPTION OF THE INVENTION

[0130] The structural color in this disclosure is caused by the nanoarchitecture (also called microstructure) of nanoparticles that exhibit cholesteric order. This structure can be formed by the self-assembly of chiral nematic liquid crystals. Once a critical concentration of nanoparticles is reached under optimal conditions, the nanoparticles begin to form cholesteric helical microstructures. The particles form pseudolayers perpendicular to the cholesteric axis and parallel to the base substrate. The cholesteric pitch is defined by the 360° rotation of the director of these pseudolayers. When this pitch is within the visible spectrum, structural color is observed.

[0131] Figure 1 shows a perspective view of an exemplary sequin mold 101 with a suspension liquid dispensed into each of a plurality of receptacles 103. Figure 1 shows mold 101 containing dried sequins.

[0132] In this example, the mold 101 is made from a flexible material such as silicone. Advantageously, silicone does not adhere to the sequins when dry, allowing for easy removal. A mold release agent may be used, but it has been found that this results in a "matt" surface finish within the mold, which can have a detrimental effect on the aesthetic properties of the sequins.

[0133] 2A-2D show schematic diagrams of a mold 101 and a receptacle 103. Each receptacle 103 shown in FIGS. 1-2D is circular in shape, although other receptacle shapes may be used as described above. The receptacle 101 is formed by a circular wall 105 protruding from the surface of the mold 101. In this example, a receptacle 103 is created that has the same base level as the rest of the mold 101; however, in other examples, the base of the receptacle 103 may not be flat and / or at the same level as the rest of the mold 101. For example, the base of the receptacle 103 may be indented or patterned to create a 3D sequin.

[0134] Also inside the receptacle 103 is a rod 107 that extends upright from the base and parallel to the wall 105 of the receptacle 103. In the illustrated example, each receptacle 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 wall surface is 10 mm, and the diameter of the outer wall surface is 12 mm). The rod 107 has a diameter of 1.2 mm and may be located 3 mm from the edge and 2 mm from the center, as shown in more detail in Figure 2D. For receptacles 103 of these dimensions, it is preferable to dispense approximately 300-330 microliters of solution into each receptacle 103. Preferably, more solution than the volume of the receptacle is dispensed, resulting in an initial dome-like liquid shape (due to surface tension). Once the suspension dries and the water evaporates, a flat sequin is obtained.

[0135] The mold 101 shown in Figures 1 and 2 was made from Smooth-On Mold Star™, purchased from Bentley® Advanced Materials and cast on an acrylic cast / die, and machined using a computer-controlled CNC (computer numerically controlled) machine.

[0136] In some instances, a vacuum degassing process may also be employed to remove air bubbles from the mold and ensure accurate formation of the rod.

[0137] However, in some instances, instead of using a mold made from silicone, a base layer can be used that also functions as a mold. The base layer and CNC are then fused together and cut out as a single component by a cutting die (designed to fit the mold). Again, the aqueous CNC evaporates, creating a chiral structural color pattern within the mold.

[0138] FIG. 3 shows a perspective view of a robot 150 dispensing a suspension into each receptacle 103 of a mold 101 (such as mold 101 in FIGS. 1-2D). The suspension contains cellulose nanocrystals (CNCs) dissolved in a solvent (in this case, water). The suspension may contain 10 to 1 wt% cellulose nanocrystals. Preferably, the suspension contains 2 wt% cellulose nanocrystals. A plasticizer is also added to the suspension, which in this example is sorbitol. The plasticizer may be added at a rate of 10% of the dry mass of the cellulose nanocrystals.

[0139] Cellulose nanocrystals from a variety of sources can be used, including nanocrystals produced by acid hydrolysis from various cellulose materials, including but not limited to wood pulp, filter paper, cotton, and waste cellulose sources. Cellulose nanocrystals are available commercially from commercial suppliers.

[0140] An example of cellulose nanocrystals that can be used is CelluForce NCC® NCV100NASD90. These cellulose nanocrystals are extracted from cellulose, the primary building block of trees and plants, and are a redispersible powder of uniform acyclic nanometer crystals. The size, shape, and charge of these particles result in unique behavior in suspension. The high chemical reactivity of the crystal surface allows CelluForce NCC® to be customized for a variety of applications. The properties of the cellulose nanocrystals are shown in Table 1 below. [Table 1]

[0141] The suspension is dispensed using a custom-built dispensing robot, as shown in Figure 3. The dispensing robot is configured to dispense a selected volume of liquid into each receptacle.

[0142] For receptacles 103 having a diameter of 10 mm and a wall height or depth of 0.3-0.5 mm, 300 μL of suspension is preferably provided or dispensed into each receptacle. Due to the surface tension of the suspension, this results in a dome-shaped "bubble" of liquid suspension 110 within each receptacle 103, as can be seen in FIG. 3. However, as water evaporates from the suspension during the drying process, this dome-shaped bubble 110 decreases in size, resulting in a generally flat, solid, iridescent sequin. FIG. 2B shows a cross-section of a receptacle 103 of a mold 101 filled with solution.

[0143] Preferably, the suspension may be dispensed into each of the receptacles 103 of the mold 101 adjacent to the rod 107, as shown in Figure 2D as preferred dispense location 111. In the example shown, if the rod 107 is on the y-axis from the centerline, then the preferred dispense location 111 is approximately 1 mm from the centerline of the receptacle 103 on the x-axis and 3 mm from the rod 107 on the y-axis.

[0144] Advantageously and surprisingly, dispensing the solution adjacent to the rod means that the CNC material self-assembles around the sewing holes, avoiding punching holes and imparting a circular rainbow pattern. Furthermore, dispensing the solution adjacent to the rod was also found to reduce the likelihood of air bubbles forming in the solution (resulting in defective sequins).

[0145] Once all of the receptacles 103 of the mold 101 are filled, the mold 101 is subjected to a drying process that is controlled to prevent drying from occurring too quickly, which would result in sequins that have weaker iridescence and may also be more fragile, as will be described in more detail below with reference to Figure 6.

[0146] It has been found that the sequins should preferably be dried at ambient temperature, for example, between 15°C and 25°C, preferably between 22°C and 23°C, and even more preferably at 23°C. Preferably, humidity should be kept constant at between 48% and 65%, preferably 50%. Optionally, a uniform airflow can be directed directly above the top of the mold 101 to enhance drying, but it is important that the airflow is uniform. This is because it has been found that without uniform airflow, the humidity in the center of the mold 101 may be higher, causing the sequins at the edges of the mold 101 to dry more quickly, which can result in sequins at the edges of the mold 101 having different iridescent qualities compared to sequins made towards the center of the mold 101. For fashion houses that require all sequins on a garment to look the same, sequins with different iridescent qualities are not always acceptable.

[0147] Additionally or alternatively, the mould 101 may be dried by heating at 40°C, 105°C and / or 65°C and then pressed against the dried sequins in a heat press at 200 bar, which flattened the sequins and showed improved hydrophobicity, but made the sequins more brittle during sewing.

[0148] It is desirable to have a flexible mold 101 so that the sequins are easily released when the mold is bent by hand.

[0149] Figure 4 shows a photograph of an exemplary rainbow sequin 400 produced in accordance with an embodiment of the present disclosure. As can be seen in Figure 4, the rainbow sequin 400 has a natural circular rainbow pattern, which occurs due to the CNC suspension self-assembly as it dries within the receptacles of the mold. The rainbow sequin 400 also has holes 405 formed by the rods 107 within each receptacle 103. Advantageously, the holes 405 can be threaded so that the sequin may be sewn into a textile or garment.

[0150] 5 shows an exemplary process flow diagram of an exemplary method 1000 for making rainbow sequins. In step 1010, a suspension of cellulose nanocrystals and a plasticizer 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 create dried rainbow sequins. In step 1040, the mold 101 is bent to release the dried rainbow sequins from the mold 101.

[0151] In some instances, the brittleness of the sequin may be improved by adding additives, synthetic polymers or plastics.

[0152] In some instances, instead of forming the sequins in a die, a sheet of CNC material may be formed in a roll-to-roll process and the sequins manufactured using traditional die-cutting methods, however, there is still waste and the material may not have the mechanical properties necessary to withstand the impact of the die-cutting equipment.

[0153] In some examples, existing or novel formulations of cellulose plastic sheets (which may be washable) may be coated with a colored metal (such as aluminum) instead of forming sequins in mold 101. This option does not reduce the amount of colored pigment used or the amount of colored metal used, and is more resource intensive than the methods described above with reference to Figures 1-5.

[0154] Another means of forming sequins is to layer cellulose films (perhaps fibrillated cellulose for its mechanical properties rather than its crystalline nature), with the layers at specific distances selected to refract light and create structural colors. This creates an overall color effect. To mimic the colors achieved with the rainbow sequins described above with reference to Figures 1-5, the film can be inkjet printed with pigment colors to create color rings, or structural colors can be created, or patterns can be created with magnets. This then needs to be printed to fit a die-cut tool.

[0155] As mentioned above, if the sequin dries too quickly, the iridescence can be reduced. Figure 6, which plots the drying time 603 and color intensity 601 of a 300 μL solution at 10-15% relative humidity versus temperature, shows that if the sequin dries slowly enough (in this example, about 6 hours at about 20-23°C), the iridescence, and therefore the perceived color intensity 601, improves.

[0156] General case While the present specification has described the use of a particular type of flexible mold to form a particular shape (e.g., a sequin), the method and resulting film are not so limited. Similarly, while the methods described herein have been illustrated with reference to aqueous solutions of cellulose nanocrystals, the method and resulting film are not so limited. In particular, the physical self-assembly of a bound suspension within a domain is not unique to aqueous solutions of cellulose nanocrystals dried within flexible molds formed from silicone rubber. The same principles may be applied to the self-assembly of microstructures formed from any anisotropic nanocrystals (formed from organic materials, inorganic materials, or blends of the two) by drying a suspension of anisotropic nanocrystals in a solvent. Furthermore, confinement of a suspension to the contours of a desired shape (not limited to a sequin) may be achieved by a variety of modalities, including molds and / or templates.

[0157] Furthermore, the relative surface energies of the interfaces between the suspension, air, mold or template, and self-assembled microstructures may control the shape of the film formed by drying the suspension. Without wishing to be bound by theory, this is thought to occur due to an anchoring effect caused by these interfacial energies, controlling the orientation of the domains relative to the mold and their orientation at the edges. The hydrophobicity of the mold or template increases the contact angle, preventing the suspension from depositing on the sides. This prevents / reduces the coffee ring effect (a ring-shaped deposition of material at the edge of a droplet due to capillary flow) and creates an anchoring effect to the substrate. As the liquid crystal domains seed, grow, and deposit at the interface between the mold and the suspension, a continuous change in the helical axis occurs.

[0158] The mold may be formed of any material that has a surface energy with the anisotropic nanocrystals such that the formation of the self-assembled microstructure is energetically favored at the air-suspension-mold interface (edge / 1D interface) compared to the suspension-mold interface (surface / 2D interface). The mold may be formed of any material that has poor adhesion to the self-assembled microstructure of the anisotropic nanocrystals, e.g., a contact angle of 50° or greater. The contact angle can be measured by performing optical tensiometry using a contact angle goniometer. The mold may also be made of materials and coatings that create a hydrophobic effect.

[0159] In particular, the shape or profile of the membrane around the perimeter may be controlled to avoid sharp or thin edges at the perimeter. As a result, crack initiation / propagation may be suppressed at the perimeter (which may correspond to maximum stress in many loading scenarios). This edge effect creates a membrane that is less susceptible to fracture or cracking than previous membranes formed from self-assembled microstructures of anisotropic nanocrystals. Examples of membrane shape and edge effects that may be obtained are shown in Figures 11 through 14F, described below.

[0160] The resulting film, having a self-assembled microstructure of anisotropic nanocrystals, also exhibits similar interactions with light as the iridescent sequins described above, provided that the typical spacing between the anisotropic nanocrystals is comparable to that of visible light. In other examples, the spacing may be controlled to induce structural color and / or reflection of invisible wavelengths of light (e.g., infrared or ultraviolet wavelengths).

[0161] 7, 11 and 12, the general case of forming membranes 2000a, 2000b in a mold 2001 is shown.

[0162] A volume 2002 of suspension 2003 is dispensed into mold 2001, for example, using a pipette 2004 (which may be manual or automated). Suspension 2003 includes anisotropic nanocrystals suspended in a solvent. The anisotropic nanocrystals may be bacterial cellulose nanocrystals or neutralized cellulose nanocrystals. Examples of suitable anisotropic nanocrystals other than cellulose include, but are not limited to, chitin, inorganic materials, silicon, silica, and polystyrene. Examples of solvents other than water include, but are not limited to, ethanol, glycerin, glycerol, IPA, methanol, acetone, etc.

[0163] Mold 2001 generally takes the form of one or more wells 2005 (or receptacles), each defined by a wall 2006 upstanding from a base 2007. Typically, walls 2006 may be integrally formed with base 2007. However, if a sufficiently good seal can be obtained (whether by pressure or otherwise), walls 2006 may be separable from base 2007 following drying of membranes 2000a, 2000b, e.g., to facilitate removal. Walls 2006 typically have a height h of 3 mm or less. Height h may be significantly lower or higher depending on the concentration of suspension 2003. Wall 2006 height h may be reduced to 0.01-2.9 mm for cellulose nanocrystal concentrations greater than 2-8% wt, with hole rod heights of 0.3-3.2 mm and membrane 2000a, 2000b (e.g., sequin) diameters D of 4-12 mm.

[0164] Each well 2005 (particularly the floor / base) may be non-flat, concave, convex, or have other shapes. Mold 2001 can be made from a variety of materials, examples of which include, but are not limited to, silicone, PVC, other resins and polymers (including biopolymers and / or synthetic polymers). Mold 2001 can also be made from glass or metal with natural or treated surfaces. Other materials for mold 2001 may include, for example, polystyrene, acrylic, PVC, urethane, wood, steel, aluminum, other alloys, paper, cardboard, textiles, composite materials, and various grades of silicone.

[0165] Volume 2002 is preferably larger than that defined by height h of wall 2006, so that surface tension of suspension 2003 prevents overflow of wall 2006. Mold 2001 may be flexible, for example formed from silicone rubber, as described hereinbefore. Alternatively, mold 2001 may be rigid. In some instances, one of base 2007 and wall 2006 may be flexible, while the other element is rigid.

[0166] Wells 2005 may be arranged to form an array, with each well 2005 being considered a separate mold 2001 within the meaning of this specification. Multiple wells 2005 may have the same shape, although this is not required and it may be desirable to provide a variety of well 2005 shapes (e.g., square, circular, etc.) on a single base 2007. If wells 2005 are not identical, different volumes 2002 of suspension 2003 may be dispensed into each well.

[0167] The dispensed volume 2002 of suspension 2003 is then dried to form a film 2000a, 2000b with a self-assembled microstructure of anisotropic nanocrystals. There are two main cases of interest, shown in Figures 11 and 12, respectively.

[0168] With particular reference to FIG. 11, a schematic cross-sectional view of a first type of membrane 2000a (hereinafter "first membrane") is shown, which has a "recurved" edge effect.

[0169] The first type of film 2000a is formed of a self-assembled microstructure of anisotropic nanocrystals and has a center of gravity 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 that contacts air upon completion of the drying process. The first film 2000a is generally of consistent thickness throughout the bulk region 2012, including the center of gravity 2008. However, around at least a majority of the perimeter 2009, the first film 2000a curls back on itself, forming a recurved portion 2013.

[0170] The recurved portion 2013 may have a thickness similar to that of the bulk region 2012, but may be thinner or thicker in some cases. The recurved portion 2013 is spaced a distance d from the perimeter 2009. r The recurved portion 2013 extends back (i.e., back toward the center of gravity 2008) and is generally parallel to the bulk region 2012 (on average, since the bulk region 2012 need not be flat). The recurved portion 2013 is a distance h from the top surface 2010 of the bulk region 2012, which recurves back onto itself. s The distance between the two electrodes is approximately 1 / 2 inch, which in some cases can be effectively zero (i.e., they are touching).

[0171] If the mold 2001 is circular, the perimeter 2009 is also circular, with a diameter D that corresponds generally to the well 2005 of the circular mold 2001. In this case, the parameter d of the recurved portion 2013 r , h s , the overall shape and thickness are typically consistent throughout the circular perimeter 2009. If the mold 2001 is not circular, but instead is square, rectangular, etc. (see also FIG. 15), the parameters d of the recurved portion 2013 r , h sThe overall shape and thickness typically vary with position around perimeter 2009. For example, the midpoint of a rectangular perimeter 2009 will be different compared to the corner points of the same rectangular perimeter 2009. However, under the right conditions (described below), recurved portion 2013 will be present around at least most of perimeter 2009.

[0172] The first membrane 2000a is generally thin in one dimension, but is not necessarily flat / planar (and in many applications is intentionally non-flat), and does not enclose a volume. The first membrane 2000a (specifically its recurved portion) may be recurved back onto itself a distance at least equal to the thickness of the membrane at the center of gravity 2008 (taking the center of gravity as representative of the bulk region 2012). If the first membrane 2000a is not flat, the perimeter 2009 may be determined by projecting the outline of the first membrane 2000a onto a plane perpendicular to the thickness of the membrane at the center of gravity 2008.

[0173] In this way, sharp or thin edges may be avoided at perimeter 2009. As a result, crack initiation / propagation may be inhibited at perimeter 2009 (which may correspond to maximum stress in many loading scenarios). This edge effect creates first membrane 200a that is less susceptible to fracture or cracking than previous membranes formed from cellulose nanocrystals (or similar materials). Recurved portion 2013 may still terminate in a sharp / thin edge without losing the desired edge effect at perimeter 2009 (see also FIGS. 13A and 13E).

[0174] Without wishing to be bound by theory, it is believed that the formation of first membrane 2000a having recurved portion(s) 2013 is facilitated by a continuum of structural alignment that governs the structural anchoring effect to mold 2001 or template 2015. This results in alignment and continuous direction of membrane 2000a, resulting in the recurved shape, as seen experimentally in Figures 17A, 17B, and 17D. This shape of membrane 2000a differs from that of prior art films formed in plastic or glass Petri dishes. In such prior art films, the anchoring effect to the Petri dish is dominant, resulting in an edge effect where the helical axis changes abruptly. This typically results in a weak point in the structure at the edge where the film reorientates perpendicular to the wall of the Petri dish. This is commonly seen in the literature where material is formed on the side of a 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 films are released (or attempted to be released) from a Petri dish, their edges often separate from the main film and fracture. While the edge regions do not always separate, this defect inherently creates a weak point in the structure.

[0175] With particular reference to FIG. 12, a schematic cross-sectional view of a second type of membrane 2000b (hereinafter "second membrane") having a blunt edge effect is shown.

[0176] The second membrane 2000b is substantially the same as the first membrane 2000a, except that it does not include edge effects in the form of recurved portion(s) 2013. Instead, the cross-sectional profile of the second membrane 2000b has a minimum radius of curvature r when moving from the upper surface 2011 to the lower surface 2010 (or vice versa) about any point on the perimeter 2009. min is controlled to be at least 0.1 times the thickness of the second film 2000b at the center of gravity 2008 (taken as representative of the bulk region 2012 away from any edge effects), for example, by following the path 2014 shown in FIG. 12. FIG. 12 shows the minimum radius of curvature r min shows a simple (special) case where r is approximately equal to half the thickness of the second membrane 2000b at the center of gravity 2008, but more complex cases are shown in Figures 14A to 14F. In practice, the minimum radius of curvature r min is typically significantly smaller than half the thickness of the second membrane 2000b at the center of gravity 2008, but must be controlled to be at least 0.1 times this thickness.

[0177] As with first film 2000a, second film 2000b avoids the formation of sharp or thin edges at perimeter 2009 (in contrast to prior art examples of films formed using cellulose nanocrystals). As a result, by inhibiting crack initiation / propagation at perimeter 2009, second film 2000b may be less susceptible to breaking or cracking than prior art cellulose nanocrystal films (or similar films).

[0178] Without wishing to be bound by theory, we propose a method for controlling the minimum curvature r minThe formation of the second film 2000n having a thickness of 1000 nm may be facilitated by a lateral boundary due to pinning or by a physical boundary. In either case, thinning / spreading of the material is limited. This may be achieved by the repulsive force of the material in the mold 2001 and / or by the template 2015 creating a high contact angle. The second film 2000b may be formed with a high concentration of anisotropic nanocrystals in the suspension 2003 (e.g., 3-10 wt%). If the concentration is too low (e.g., less than 3 wt%), the resulting bulk region 2012 of the film 2000b may be too thin. This may cause the angle of the cholesteric axis of the anisotropic nanocrystals to change at or near the periphery 2009.

[0179] An alternative approach to forming the second film 2000b is to first form the first film 2000a as shown in Figure 11, and then deposit more material to fill the area inside the recurved portion 2013 (e.g., one or more iterations of dispensing and drying the suspension 2003) to create the shape of the second film 2000b, which provides a structure without sharp points, weak points, and / or fragile edges around the perimeter 2009.

[0180] Thus far, this specification has described the use of a mold 2001 containing one or more wells 2005 or receptacles 103 to confine the suspension 2003 during drying to form membranes 2000a, 2000b of a desired shape, although walls 2006 are not required and confinement may be achieved in other ways, examples of which include the use of surface tension / contact angle control.

[0181] Referring also to FIG. 8, a template 2015 for forming membranes 2000a, 2000b is shown in schematic cross section.

[0182] 7, 11 and 12 may be carried out as described hereinbefore, except that a template 2015 is used in place of mold 2001. Template 2015 includes one or more first or "wettable" regions of a template substrate 2017 that are wetted by suspension 2003, with each wettable region 2016 being surrounded and defined by one or more intervening second or "non-wettable" regions 2018 that are not wetted by suspension 2003. A required volume 2002 of suspension 2003 is dispensed onto each wettable region 2016 and held in place by surface energy effects.

[0183] If the contact angle of a drop of suspension 2003 contacting region 2016 is less than or equal to 90°, suspension 2003 may be considered to wet region 2016. If the contact angle of a drop of suspension 2003 contacting region 2018 is greater than 90°, suspension may be considered to not wet region 2018. For example, if suspension 2003 is aqueous, then wettable region 2016 is hydrophilic and non-wettable region 2018 is hydrophobic.

[0184] Pinning of the suspension 2003 sufficient to serve as a template 2015 may be achieved with a contact angle of 60-75° or greater, an example of which is aqueous suspension 2003 on silicone rubber.

[0185] 8, the template substrate 2017 is wettable and the non-wettable regions 2018 are defined by applying a thin coating. Of course, depending on the substrate, alternative surface modifications of no appreciable thickness may be used to alter the wettability, examples of which include chemical activation.

[0186] The template substrate 2017 may take any suitable form, examples of which include, but are not limited to, a film, a sheet, a plate, etc. In some examples, the template substrate 2017 may take the form of a surface of a three-dimensional object. In other examples, the template substrate 2017 may take the form of a second film 2000a, 2000b of the same material. In general, the template substrate 2017 may be porous or non-porous. Its pores may be closed-cell or open-cell (open-cell pore penetration may be avoided by controlling the surface energy relative to the suspension 2003 and / or controlling the size of the anisotropic nanocrystals relative to the pores).

[0187] Template substrate 2017 may include or be formed from a polymer, examples of which include, for example, polystyrene, acrylic, polyvinyl chloride, urethane, polyurethane, etc. Template substrate 2017 may include or be formed from a metal, examples of which include, for example, steel, aluminum, or other alloys (with natural or treated / coated surfaces), provided that there is no adverse reaction with the solvent of suspension 2003. Template substrate 2017 may include or be formed from paper, card, wood, glass, fabric, textile (synthetic or natural), fiber mat, silicone rubber (various grades), natural rubber, or laminate, or two or more such materials.

[0188] 9, in one specific implementation of mold 2001, one or more wells 2005 may be formed by embossing a mold substrate 2019 to form embossed mold walls 2020. The mold substrate 2019 may be of any type or material described in connection with the template substrate 2017.

[0189] 10 , in other examples implementing mold 2001, one or more wells 2005 may be formed by debossing mold substrate 2019 to form debossed regions 2021. Also, mold substrate 2019 may be of any type or material described in connection with template substrate 2017.

[0190] Such an embossed / debossed mold substrate 2019 may be formed to create a mold 2001 that is intended to be temporary or semi-temporary, allowing for direct deposition of a film 2000a, 2000b in a designed shape onto the prepared mold substrate 2019. In other examples, it may be intended that the film 2000a, 2000b remain adhered to the embossed / debossed mold substrate 2019.

[0191] Example of the first membrane The structure of the first membrane 2000a can be better understood with reference to several (non-exhaustive) examples.

[0192] Referring also to FIG. 13A, a schematic cross-sectional view of a first example 2022 of the first membrane 2000a is shown.

[0193] The first example 2022 has a recurved portion 2013 that tapers to a thickness that is thinner (and in some implementations may be much thinner) than the thickness of the bulk region 2012 (e.g., the thickness taken at the center of gravity 2008). Nevertheless, the first example 2022 remains resilient to cracking due to the thickness of the perimeter 2009 and the wide radius of curvature provided by the edge effect of the recurved portion 2013.

[0194] In common with other examples of first film 2000a (see FIGS. 13B-13G), recurved portion 2013 may also prevent perimeter 2009 of film 200a from snagging and / or damaging other materials, for example, when used on textiles. When applied as a glitter, this shape prevents sharp edges that can be dangerous when using glitter in cosmetics or other products applied to the skin (e.g., due to micro-abrasion and / or potential transfer to a user's eyes or other sensitive films). Damage to the surface of an object to which first film 2000a, such as first example 2022, is applied / coated may also be avoided.

[0195] Referring also to FIG. 13B, a schematic cross-sectional view of a second example 2023 of the first membrane 2000a is shown.

[0196] The second example 2023 has a recurved portion 2013 that continues to recurve back on itself such that the edge points back down towards the top surface 2011 of the bulk region 2012. This may improve rigidity by forming a tubular structure around at least a portion of the perimeter 2009. Additionally, the edges, which may be thinner, may be protected by curving all the way back towards the structure.

[0197] While the second example 2023 is shown with the recurved portion 2013 having substantially the same thickness as the bulk region 2012, this is not required. Instead, the thickness of the recurved portion 2013 of the second example 2023 can be reduced and / or tapered, as described in connection with the first example 2022. The tapered thickness of the second example 2023 can still fracture, but if this occurs, potentially sharp edges of the tapered portion will curl inward toward the bulk portion 2012 of the corresponding fragment, reducing the likelihood of damage to the outer material.

[0198] Referring also to FIG. 13C, a schematic cross-sectional view of a third example 2024 of the first membrane 2000a is shown.

[0199] The third example 2024 has a separation height h that is small compared to the thickness of the membrane 2000a. s 2000a has a recurved portion 2013 that extends back toward the center of gravity 2008 with (or even with) very little / vibrational contact. In other words, the recurved portion 2013 lies substantially flat against the top surface 2011 of the bulk region 2012. This type of compact profile can help provide improved toughness against cracks initiating / propagating from the perimeter 2009 while minimizing any increase in stiffness (from moment of area) of the membrane 2000a.

[0200] The shape of the third example 2024 may provide further improvement in mechanical strength at the periphery 2009 and may also result in less variation in the helical axis of the anisotropic nanocrystals, which directly impacts the observed structural color. In this way, the angular variation in the reflected color with viewing angle may be reduced. The third example 2024 has a flatter shape with less pronounced edge profiles compared to the first example 2022. The third example 2024 may be advantageous if the film 2000a has high flexibility. This flexibility can be induced by varying the formulation (wt% of anisotropic nanocrystals), the film 2000a's thinness (e.g., 0.5-40 μm), humidity (e.g., 60% or more), and drying rate (e.g., 24 hours or more).

[0201] Although the third example 2024 illustrates that the thickness of the recurved portion 2013 is substantially the same as the thickness of the bulk region 2012, this is not required. Instead, the thickness of the recurved portion 2013 of the third example 2024 can be reduced and / or tapered, as described in connection with the first example 2022.

[0202] Referring also to FIG. 13D, there is shown a schematic cross-sectional view of a fourth example 2025 of the first membrane 2000a.

[0203] 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 molding base 2007 that defines all or part of a 3D shape. In the example shown, a first portion of the bulk region 2012a forms a first flat surface (or flat facet), which transitions to a second portion of the bulk region 2012b to form a second sloping surface(s) or sloping facet(s). For example, the lower surfaces 2010a, 2010b may have the appearance of a portion of a surface, examples of which include a dodecahedron, coidoid, pyramid, sphere, tetrahedron, torus, or any other curved or polyhedral shape (regular or irregular).

[0204] The fourth example 2025 is shown in comparison to the third example 2024, although a similar 3D mold shape may be used in either one of the first example 2022 and / or second example 2023.

[0205] To achieve 3D shapes, the viscosity of the suspension 2003 needs to be high and the material selection needs to promote some pinning and / or adhesion of the suspension 2003 and / or the anisotropic nanocrystals to the mold 2001 or template 2015 so that the self-assembled microstructure of the anisotropic nanocrystals does not settle to the bottom of the mold.

[0206] Referring also to FIG. 13E, there is shown a schematic cross-sectional view of a fifth example 2026 of the first membrane 2000a.

[0207] Fifth example 2026 is the same as second example 2023, except that it illustrates a situation in which at least a section of recurved portion 2013 has been damaged, for example by fracture due to downwardly applied pressure (relative to the cross section shown), leaving recurved portion 2013 terminating at fracture surface 2027. An edge effect at perimeter 2009 may be preserved, provided that the damage does not extend to or beyond perimeter 2009.

[0208] The fifth example 2026 is shown in comparison to the second example 2023, but also applies to any of the first example 2022, third example 2024 and / or fourth example 2025.

[0209] Referring also to FIG. 13F, there is shown a schematic cross-sectional view of a sixth example 2028 of the first membrane 2000a.

[0210] Unlike the first example 2022 through the fifth example 2026, the bulk portion 2012 of the sixth example 2028 is not flat or faceted, but instead has curvature. The curvature may be caused by shrinkage / residual strain upon drying, or may be intentionally introduced by the shape of the mold 2001. This curvature means that the structural color reflections are observable over a wider range of viewing angles. When used to form glitter, this curvature may also enhance the adhesion of the film 2000a to the skin (or other surface) via a suction mechanism due to the concave shape.

[0211] Any of the first through fifth examples 2022 through 2026 may include a bulk portion 2012 having intentional or unintentional curvature.

[0212] Referring also to FIG. 13G, there is shown a schematic cross-sectional view of a seventh example 2029 of the first membrane 2000a.

[0213] Example 1 2022 through Example 6 2028 show recurved portion(s) 2013 that recurve in a single direction of rotation, i.e., toward the center of gravity 2008. In contrast, example 7 2029's recurved portion(s) 2013 have a "double recurve" shape, first recurving toward the center of gravity 2008 and then changing direction of rotation to recurve toward the periphery 2009.

[0214] Any of the first example 2022 through the sixth example 2028 may alternatively include recurved portion(s) 2013 having a "double recurved" shape similar to the seventh example 2029.

[0215] The seventh example 2029 can be advantageous when the first film 2000a has high flexibility. This flexibility can be induced by the formulation, film thinness, humidity (e.g., 60% or more), and drying rate (e.g., 24 hours or more). The double-recurved shape is particularly advantageous for slow drying. This slow drying allows the suspension to anchor to the mold walls for the first 50% of the drying process, and then the walls collapse, slowly curling inward, leading to "tails" that curve in the opposite direction.

[0216] Example of second membrane The structure of the second membrane 2000b can be better understood with reference to several (non-exhaustive) examples.

[0217] Referring also to FIG. 14A, a schematic cross-sectional view of a first example 2030 of second membrane 2000b is shown.

[0218] First example 2030 does not include recurved portion 2013, but rather, around the periphery, first example 2030 includes a rim portion 2031 extending upward (relative to lower surface 2010) around at least a portion of periphery 2009. Rim portion 2031 is shown with the same thickness as bulk region 2012, but may have a reduced thickness and / or be tapered. Rim portion 2031 extends to a height hr above bulk region 2012, and this height h r should not exceed about 3 mm. More generally, the height h r is preferably 50 times or less the thickness of bulk region 12 (eg, as represented by the thickness at center of gravity 2008).

[0219] Rim portion 2031 may form a corresponding height of wall 2006 that exceeds the thickness of bulk region 2012 of film 2000b. Without wishing to be bound by theory, it is believed that the formation of rim portion 2031 results from the pinning of the self-assembled microstructure of anisotropic nanocrystals to the edge of mold 2021, the thickness of bulk portion 2012, and / or the drying rate, which occurs when concentrations are 3-8 wt % or when high viscosity additives (e.g., hydroxypropyl cellulose) are used.

[0220] Referring also to FIG. 14B, a schematic cross-sectional view of a second example 2032 of the second membrane 2000b is shown.

[0221] The second film 2000b shown in FIG. 12 has a minimum curvature radius r min , which is equal to about half the thickness of the bulk region 2012 (e.g., as represented by the thickness at the center of gravity 2008). However, this is not required, and as shown in the second example 2032, the minimum radius of curvature r min may be less than half the thickness of the bulk region 2012, but must be at least 0.1 times this thickness.

[0222] The second example 2032 may also include the rim portion 2031 described in connection with the first example 2030.

[0223] The second example 2032 may be useful in applications where smooth edges are desired to form objects (whole or in part) such as glitter, tinsel, rhinestones, confetti, and other free-standing film applications. The edge profile of the second example 2032 may provide an embossed feel to the coating (as perceived against human skin), giving the coating an appealing luxury effect.

[0224] Referring also to FIG. 14C, a schematic cross-sectional view of a third example 2033 of the second membrane 2000b is shown.

[0225] The bulk region 2012 of the third example 2033 is curved, and in the illustrated example, the schematic cross section shows an S-shaped bend, but it may also be an out-of-plane pillar or part of a more complex shape (e.g., a saddle). This bend may be caused by drying / residual strain (which may be intentionally induced) or the shape of the mold 2001. A film 2000b with curvature may be used for certain visual effects because at least a portion of the surfaces 2010, 2011 will satisfy the diffraction / reflection conditions from the self-assembled microstructure of anisotropic nanocrystals over a wider range of viewing / illumination angles.

[0226] Either the first example 2030 and / or the second example 2032 can be modified to have a curved bulk region 2012.

[0227] Greater curvature of bulk region 2012 may be produced, for example, by using a highly concentrated 4-8 wt % suspension of cellulose nanocrystals in aqueous suspension 2003. Additionally or alternatively, curvature may be enhanced / promoted by including high viscosity additives (such as sorbitol, hydroxylpropyl cellulose, etc.) in suspension 2003. Additionally or alternatively, curvature may be enhanced / promoted by drying in oil or at high humidity (e.g., 60% or higher).

[0228] Referring also to FIG. 14D, a schematic cross-sectional view of a fourth example 2034 of the second membrane 2000b is shown.

[0229] The fourth example 2034 has a first portion of bulk region 2012a that is relatively thinner than one or more relatively thicker second portions of bulk region 2012b formed around at least a portion of perimeter 2009. A minimum thickness 2035 of the first portion of bulk region 2012a may, but need not, coincide with center of gravity 2008. This is achieved by a minimum radius of curvature r min 20 shows that in some instances, the thickness of the membrane 2000b at the center of gravity 2008 may be greater than the thickness of the membrane 2000b at the center of gravity 2008.

[0230] Any of the first example 2030, second example 2032 and / or third example 2033 can be modified to have a relatively thicker second portion of bulk region 2012b formed around at least a portion of perimeter 2009.

[0231] Example 4 2034 may allow for less material usage, reducing the overall weight of film 2000b while still producing the same thick edge effect at perimeter 2009. Example 4 2034 may be advantageous by increasing the coffee ring effect (where capillary flow induces particles to settle at the edge of the droplet), by reducing the viscosity of suspension 2003 by avoiding high viscosity additive concentrations, or by lowering the wt% concentration of anisotropic nanocrystals (e.g., in the range of 0.5-4% for cellulose nanocrystals in aqueous suspension 2003), which allows capillary flow. Additionally or alternatively, example 4 2034 may be advantageous by one or more of: shortening drying time (e.g., less than 24 hours for a 2 wt% suspension), reducing humidity (e.g., 30-50%), increasing airflow, or increasing temperature during drying (e.g., 25-45°C).

[0232] Referring also to FIG. 14E, there is shown a schematic cross-sectional view of a fifth example 2036 of the second membrane 2000b.

[0233] The fifth example 2036 is the same as the third example 2033, except that the bulk region 2012 is curved in only a single direction.

[0234] Any of the first example 2030, the third example 2033 and / or the fourth example 2034 can be modified to have a curvature similar to the fifth example 2036.

[0235] The concave effect exhibited by Example 5 2036 results in a wider range of angles at which the structural color can be observed. Glitter formed according to Example 5 2036 may have improved adhesion / holding to skin (or other surfaces) due to the suction cup effect of the concave shape. Example 5 may be enhanced by slowing down the drying time and / or using additives with larger lateral size (e.g., graphene with a diameter of 200-300 nm).

[0236] Referring also to FIG. 14F, there is shown a schematic cross-sectional view of a sixth example 2037 of the second membrane 2000b.

[0237] 3D shapes require lower repulsive forces between the substrate and the suspension (compared to flat shapes) to allow pinning to the mold 2001 instead of pooling the suspension 2003 at the bottom of the mold 2001. The vertices of these shapes have a continuous structure at the bend, similar to the edge effect.

[0238] Like the fourth instance 2025 of the first membrane 2000a, the sixth instance 2037 of the second membrane 2000b was formed in a mold 2001 having a molded base 2007 that defines all or part of a 3D shape.

[0239] Any of the first example 2030 through the fifth example 2036 can be modified to have sharp transitions between surfaces / facets using a mold 2001 having a molding base 2007 that defines all or part of the 3D shape.

[0240] The film dried as a single unit To obtain the beneficial edge effects described herein, each membrane 2000a, 2000b (and any instances thereof) must be formed by drying as a single unit. Cutting shapes from a single large bulk region 2012 would not produce the relevant edge effects and could potentially introduce sharp edges / cracks that would adversely affect toughness (against fracture).

[0241] The origin of films 2000a, 2000b formed integrally by drying a suspension containing anisotropic nanocrystals may be determined by examining the directional alignment of the anisotropic nanocrystals. They may also exhibit edge effects due to self-assembly. This self-assembly typically propagates inward from the boundary between air, mold 2001 / template 2015, and suspension 2003, as opposed to occurring simultaneously throughout the suspension 2003. This is similar to microstructural edge effects evident in other systems (e.g., injection-molded polymers, cast alloys).

[0242] Such microstructural edge effects (as opposed to the geometric edge effects previously described herein) are typically (but not exclusively) manifested in the average directional alignment of the anisotropic nanocrystals and may be determined by several means, examples of which include, but are not limited to, the following: Microscopic examination of fracture surfaces (e.g., those intentionally produced by breaking) Microscopic examination of cross sections (e.g. polished) X-ray crystallography to determine the orientation (sometimes called "texture") of anisotropic nanocrystals, or If the film is at least partially transparent, by inspecting the film 2000a, 2000b using visible light between crossed polarizers.

[0243] The latter approach, inspection using visible light between crossed polarizers, is particularly preferred due to the relative ease and simplicity of the method.

[0244] If the edge effects on the directional alignment of the anisotropic nanocrystals are substantially similar from any point on the periphery toward the center of gravity, then the film is formed integrally by drying a suspension containing the anisotropic nanocrystals. If this is not the case, then this indicates that the film was cut from a larger object (thus eliminating some edge effect regions).

[0245] Referring also to FIG. 15, examples of films 2000a with recurved edge portions 2013 and having various shapes have been produced and imaged between polarizers of different configurations.

[0246] Membranes 2000a of different shapes were produced in each silicone rubber mold 2001 (the height h of the wall 2006 of this silicone rubber mold 2001 varied between 0.1 and 0.7 cm). In each case, the suspension 2003 used was 2% wt cellulose nanocrystals in water and 10% sorbitol by dry weight. The drying time was 12 hours.

[0247] As described herein, membrane 2000a or different shapes all exhibit edge effects that change structure depending on the distance from the perimeter 2009, demonstrating that edge effects can be generated for membranes of various shapes and sizes that are not limited to circles. Photographed examples are small (0.7 cm) 2038a, medium (1.25 cm) 2038b, and large (2.5 cm) 2038c square membranes, small (1 cm) 2039a, medium (2 cm) 2039b, and large (5 cm) 2039c circular membranes, small (2.5 cm long) 2040a, medium (5 cm long) 2040b, and large (9 cm long) 2040c oval membranes, and small (1 cm diameter) 2041a and large (2 cm diameter) 2041b hexagonal membranes.

[0248] Through-holes (not labeled in FIG. 15) are provided either close to the periphery 2009 or at the approximate center of gravity 2008 .

[0249] In either case, the edge effect is observed continuously (if not uniformly) around the perimeter 2009 of each membrane 2000a.

[0250] Referring also to Figure 16, there are shown shapes 2042a, 2042b physically cut from a sheet having the same formulation as membrane 2000a shown in Figure 15. For comparison purposes, a small circular membrane 2039a and a large hexagonal membrane 2041b are also shown. Figure 16 was obtained under the same conditions as Figure 15.

[0251] The difference in material variability is clearly observed for each shape. For the hexagonal 2042a and circular 2042b shapes, there is no difference in the light interaction at the edge versus the center of the shape. In contrast, the edge effect for film 2000a is clearly evident.

[0252] In this way, membranes 2000a, 2000b formed integrally by drying as described herein are easily distinguishable from shapes of similar shape and thickness formed by cutting from a bulk film of the same material composition.

[0253] Membrane perimeter shape It should be clear from the preceding description that the membranes are not limited to a circular / sequin shape, but for the avoidance of doubt, membranes 2000a, 2000b may have a circular, oval, triangular, square, rectangular, or any other regular or irregular shape. If desired, membranes 2000a, 2000b may be formed to have shapes corresponding to letters, numbers, symbols, logos, etc.

[0254] The membranes 2000a, 2000b may be generally planar or film-like, or may have the shape of a film that conforms to the surface of a three-dimensional shape, such as membranes 2000a, 2000b formed by drying a suspension of anisotropic nanocrystals in a correspondingly shaped mold (see, e.g., Figures 13D and 14F).

[0255] These three-dimensional shapes can then be subsequently filled to create solid shapes with iridescent surface colors. Suitable filler materials include, but are not limited to, polymers such as cellulose acetate.

[0256] Microstructure and volume fraction of anisotropic nanocrystals The anisotropic nanocrystals preferably comprise at least 80% of the volume fraction of the self-assembled microstructure of the films 2000a, 2000b. More preferably, the anisotropic nanocrystals may comprise at least 90% of the volume fraction of the self-assembled microstructure. Preferably, the anisotropic nanocrystals may be uniformly dispersed throughout the volume of the films 2000a, 2000b.

[0257] Some examples are given in Table 2 along with examples of secondary materials included in the microstructure (i.e., belonging to fractions other than the anisotropic nanocrystals). [Table 2]

[0258] Self-assembled microstructures of anisotropic nanocrystals typically exhibit structural color due to the alignment and typical spacing of the anisotropic nanocrystals. In some implementations, self-assembled microstructures of anisotropic nanocrystals may be controlled to exhibit reflection at desired target wavelengths. Either effect may be controlled to occur within visible, infrared, or ultraviolet wavelengths by controlling the typical spacing of the anisotropic nanocrystals.

[0259] The color produced depends on the cholesteric pitch, the orientation of the helical axis, the degree of order in the cholesteric, and the wavelength polarization and propagation direction of the incident light.

[0260] Anisotropic nanocrystals can self-assemble into chiral nematic liquid crystals or cholesterics, then transition to a solid state (this process can occur via solvent evaporation, which causes concentration buildup), producing films 2000a, 2000b with ordered, self-assembled microstructures that can refract light and generate structural colors. This self-assembly is tunable and driven by a balance between attractive van der Waals and repulsive interactions. These interactions can be controlled by tuning multiple means (e.g., particle charge, ionic strength, etc.).

[0261] In some instances, the self-assembled microstructure of anisotropic organic nanocrystals may exhibit disorder in the relative alignment of the anisotropic organic nanocrystals, for example, by tailoring the self-assembly to produce tilted domains, poorly defined domains, small domains, or large variations in the pitch of the structure. This may be achieved by reducing the overall alignment of the anisotropic nanocrystals throughout the film 2000a, 2000b, which must occur after the suspension reaches a critical concentration during drying (typically about 4-8 wt%) and before cessation of motion (about 6-10 wt%). Where the crystalline domains align, the self-assembled microstructure may have parallel cholesteric axes across the film 2000a, 2000b, but this overall alignment may not be achieved, resulting in domains with different cholesteric axis angles. Such structures may be observed by polarized light microscopy and / or scanning electron microscopy (SEM). Such less ordered (or even disordered) microstructures can offer a variety of optical effects, such as a wider viewing angle, a pixelated glitter effect (representing tiny specks of different colors), and a range of colors that can be produced.

[0262] additives The films 2000a, 2000b need not be formed purely from, and are not formed entirely of, a self-assembled microstructure of anisotropic nanocrystals. Various types of additives may be included in the suspension 2003 and incorporated into the microstructure to modify its properties (subject to the volume / weight fraction limitations set forth hereinabove). The additives described below, as well as further additives, may be included in any combination.

[0263] The self-assembled microstructure of anisotropic nanocrystals may include one or more pigments. These pigments may be added to the suspension 2003 as separate additives that are simply incorporated into or around the self-assembled microstructure. Alternatively, the pigments may be included directly in the anisotropic nanocrystals.

[0264] The films 2000a, 2000b (or the suspension 2003 from which they are formed) may contain a mixture or blend of two or more pigments. The pigments may be inorganic or organic.

[0265] The films 2000a, 2000b may have a hue that is produced in part by structural color from the self-assembled microstructure of the anisotropic nanocrystals and in part by anything contained in the pigment.

[0266] Alternatively, if the self-assembled microstructure of the anisotropic nanocrystals does not exhibit structural color, the color of such films 2000a, 2000b may be dominated by any pigments contained therein (in combination with the color of the anisotropic nanocrystal substrate).

[0267] The suspension 2003 (and the resulting films 2000a, 2000b) may also contain additives in the form of plasticizers. Examples include sorbitol, glycerol, propylene glycol, polyethylene glycol, and organic esters. These additives may increase the mechanical strength of the films 2000a, 2000b without interfering with the self-assembly of the nanocrystals.

[0268] The suspension 2003 (and the resulting films 2000a, 2000b) may also include additives in the form of cross-linking agents, an example of which is phytic acid.

[0269] The suspension 2003 (and the resulting films 2000a, 2000b) may also include additives in the form of high contrast absorbers, examples of which include carbon black, graphite, graphene, graphene oxide, and the like.

[0270] The suspension 2003 (and the resulting films 2000a, 2000b) may also contain additives in the form of inorganic particles, an example of which is silicone.

[0271] The suspension 2003 (and resulting films 2000a, 2000b) may also include additives in the form of oils and / or waxes. If included, the oils and / or waxes may be dispersed within the self-assembled microstructure of the anisotropic nanocrystals. Additionally or alternatively, the oils and / or waxes may form a coating on the films 2000a, 2000b or may be applied as a coating thereon after drying. In some examples, the oils and / or waxes may be encapsulated by other materials or cells. The oils may be synthetic or natural, examples of which include vegetable oils, seed oils, silica-based oils, etc. The waxes may be synthetic or natural, examples of which include paraffin, rice wax, beeswax, carnauba wax, etc.

[0272] The suspension 2003 (and resulting membranes 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. Examples include hemicellulose, cellulose fibers, cellulose nanofibers, and cellulose fibrils.

[0273] The suspension 2003 (and the resulting membranes 2000a, 2000b) may also contain additives in the form of polymers such as, for example, lignin latex, polyvinyl alcohol, hemicellulose, and the like.

[0274] The polymer may function as a plasticizer or to provide cross-links between the anisotropic nanocrystals (i.e., the 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 unit(s) as the anisotropic nanocrystals.

[0275] through holes The membranes 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 integrally formed during the formation of the membranes 2000a, 2000b, rather than cut, drilled, or stamped after the membranes 2000a, 2000b are formed.

[0276] Rods or similar protrusions may be used to form through-holes, similar to that described in connection with rods 107 in connection with the example of sequins formed from cellulose nanocrystals.

[0277] When using template 15, rods or similar protrusions may be used to form the through holes. Alternatively, the through holes, or at least the thinned areas for creating the through holes, may be formed by adding a non-wettable area 2018 that is completely surrounded by the wettable area 2016.

[0278] Membrane material An example is described for the formation of films 2000a, 2000b using cellulose nanocrystals in aqueous suspension 2003. However, as discussed herein, the same principles of physical and colloidal chemistry are applicable to suspensions of a wider range of anisotropic nanocrystals in a range of different solvents / solvent blends.

[0279] Preferably, the anisotropic nanocrystals are formed from biopolymers, examples of which include, for example, chitin, cellulose nanocrystals (such as bacterial cellulose nanocrystals or neutralized cellulose nanocrystals), or mixtures where the cellulose nanocrystals or chitin induce self-assembly followed by other particles.

[0280] Articles containing membranes The membranes 2000a, 2000b described herein are often releasable from the mold 2001 or template 2015 and then mechanically free-standing. Such membranes 2000a, 2000b are not supported on a substrate. In other words, the membranes 2000a, 2000b may be freestanding.

[0281] However, there are applications in which it may be desirable to incorporate the membranes 2000a, 2000b into larger articles.

[0282] In a first example, the article (not shown) may include a membrane 2000a, 2000b supported on a substrate (not shown). The substrate may be a film, a sheet, a plate, or even the surface of a three-dimensional object. In some examples, the substrate may be a second membrane 2000a, 2000b of the same type and / or material. The substrate may be a porous material, examples of which include closed or open cells. The substrate may include or be formed from a polymer, paper, card, fabric, fiber mat, laminates of one or more of the aforementioned types, etc.

[0283] Such an article may be formed by drying membranes 2000a, 2000b directly onto a substrate (not shown), for example, by applying a non-wettable region 2018 to define a perimeter 2009. Alternatively, a wall 2006 formed of a resilient material such as silicone rubber may be attached to or pressed against the substrate for the period during which suspension 2003 is dispensed and allowed to dry.

[0284] Alternatively, the freestanding films 2000a, 2000b may be adhered to the substrate using an adhesive or may be wetted with a solvent (e.g., the same as that used in suspension 2003), depending on the material of the films 2000a, 2000b. The wetted, freestanding films 2000a, 2000b are then placed or pressed against a substrate and allowed to dry. This can be achieved with a variety of surface materials, examples of which include glass, wood, metal, and textiles. These surfaces may be non-flat. Wetting the films 2000a, 2000b allows the structure to expand, allowing slight movement of the anisotropic nanocrystals within the structure of the self-assembled microstructure and allowing the anisotropic nanocrystals to orient to the interface of the substrate and create adhesive forces.

[0285] In a second example, the article (not shown) may include films 2000a, 2000b bonded between a first layer (not shown) and a second layer. In other words, the second example of the article forms a laminate. The first and second layers may take any of the forms previously described herein in connection with the substrate (not shown) of the first example of the article (not shown). The first and second layers may be formed from a variety of materials.

[0286] In a third example, the article (not shown) may include a coating (not shown) covering at least one surface of the film 2000a, 2000b. The coating may provide a barrier layer that protects the self-assembled microstructure of anisotropic nanocrystals from moisture, chemicals to which they may be exposed (e.g., cleaning products / compositions), etc. The coating may modify or enhance the mechanical properties of the film 2000a, 2000b, for example, by increasing stiffness, filling cracks, etc. The surface of the film 2000a, 2000b not covered by the coating may be bonded to or supported on a substrate (not shown), as previously described herein in connection with the first example of the article (not shown).

[0287] Optionally, the coating may encompass a majority of the surface of the membranes 2000a, 2000b, examples of which include at least 90% of the surface, or even the entire surface of the membranes 2000a, 2000b.

[0288] By coating the films 2000a, 2000b, a wider range of properties and / or appearances may be achieved for the article. For example, a cellulose acetate coating can create a water-resistant sequin formed primarily from cellulose nanocrystals formed in the films 2000a, 2000b. In this manner, a layered article may be formed having a structurally colored core (films 2000a, 2000b) surrounded by a protective coating, providing a combination of water resistance, structural color, and mechanical strength.

[0289] In a fourth example, an article (not shown) may include films 2000a, 2000b embedded in a transparent material (not shown). For example, the films may be embedded in a clear epoxy (not shown) that is cast into a mold (not shown). The films 2000a, 2000b (or several films) are pre-placed within this mold to form the shape of the gemstone. This method may be used to create beads / costume gemstones that benefit from the optical properties of the films 2000a, 2000b.

[0290] The films 2000a, 2000b described herein, or articles (not shown) including the films 2000a, 2000b, may be used to provide, but are not limited to, sequins, sequin reels, sequin trim, sequin mesh, glitter, jewels, gems, jewelry, costume jewelry, pendants, color pieces, ear pendants, buttons, stickers, sequins, rhinestones, hot fix crystals, ornaments, beads, nail art, glass stickers, decorations, confetti, tags, tokens, tinsel, or any other type of object used or applied to provide a specular reflection, sparkle, iridescence, or similar effect to an object.

[0291] The films 2000a, 2000b described herein, or articles (not shown) including those films 2000a, 2000b, may be used to provide, but are not limited to, puzzle pieces, coasters, poker chips, trading cards, game pieces, and the like.

[0292] The films 2000a, 2000b described herein, or articles (not shown) comprising the films 2000a, 2000b, may be applied to fabrics or other surfaces by spreading a suspension comprising anisotropic nanocrystals using a screen printing process, a dot matrix printing process, a spot printing process, a UV printing process, an inkjet printing process, a flexographic printing process, a gravure printing process, a lithographic printing process, or the like.

[0293] The films 2000a, 2000b described herein, or articles (not shown) including the films 2000a, 2000b, may be used as foil replacements for fabrics, papers, cards, and the like.

[0294] The methods described herein may be used to produce films 2000a, 2000b having long, elongated shapes, such as sequin reels on a roll (sometimes called "sequin ribbons"), while maintaining edge effects around most of the periphery of each sequin that forms the reel.

[0295] Experimental characterization of shape, microstructure and optical properties See also Figures 17A-17D, which show SEM images.

[0296] SEM images were taken of the first type of membrane 2000a showing its cross section at its periphery 2009. The membrane 2000a was broken (bent and fractured) in the middle so that the cross section of the membrane 2000a could be imaged.

[0297] Figures 17A through 17D all show the film 2000a curling back on itself to form the recurved portion 2013. As the film 2000a curls back on itself, it can be seen that the pseudolayers in the microstructure remain continuous. The sample was sputter coated with 7 nm of carbon. Images were taken on a Zeiss Gemini ultra plus.

[0298] With particular reference to FIG. 17A, the edge effects observed generally correspond to a combination of those shown in FIGS. 11, 13A and 13F.

[0299] With particular reference to FIG. 17B, the edge effects observed generally correspond to a combination of those shown in FIG. 13G.

[0300] With particular reference to FIG. 17C, the edge effects observed generally correspond to a combination of those shown in FIGS. 13C and 13D.

[0301] With particular reference to FIG. 17D, the edge effects observed generally correspond to a combination of those shown in FIGS. 11, 13A and 13F.

[0302] Referring also to FIG. 18, optical micrographs of a sequin-shaped cellulose nanocrystal film 2000a are shown from a series of viewing angles.

[0303] It can be observed that the color and intensity of the structural color exhibits angle dependence, which is generated by the self-assembled cellulose nanocrystal microstructure. Images were taken with a Keyence (RTM) VHX-7000N instrument.

[0304] Referring also to FIG. 19, a 3D optical image of the cellulose nanocrystal sequin shown in FIG. 18 is shown.

[0305] An edge effect (recurved portion 2013) may be observed around perimeter 2009. The height hr of recurved portion 2013 is approximately twice the thickness at the center of gravity of the membrane. The data in Figure 19 was acquired using a Keyence (RTM) VHX-7000N instrument.

[0306] Referring also to Figures 20A and 20B, photographs of a second type of membrane 2000b are shown. Figure 20A is oriented generally in plan view. Figure 20B shows a side view of a fractured cross section of the membrane 2000b shown in Figure 20A.

[0307] The membrane 2000b in the photograph has been generated with a curved edge around the perimeter 2009, with a minimum radius of curvature r that is approximately one-quarter of the thickness at the center of gravity 2008. min The membrane 2000b in the photo was produced on a silicone rubber hydrophobic substrate (as template 2015), so that it had a curved, smooth edge instead of the recurved portion 2013 of the first type of membrane 2000a.

[0308] Referring also to FIG. 21, a scanning electron microscope (SEM) cross-sectional image of a comparative example film is shown.

[0309] The comparative film was produced using the same cellulose nanocrystal suspension 2003 as film 2000a shown in Figures 17A-17D. Instead of drying in mold 2001 as described herein, the comparative film's suspension 20003 was dispensed into a Petri dish and allowed to dry therein. The comparative film was sputter coated with 10 nm of carbon prior to SEM imaging.

[0310] In Figure 21, a fracture can be observed at the edge of the comparative film, corresponding to the point where the comparative film contacted the edge of the Petri dish. It can be seen that the pseudolayers remained well aligned and the cholesteric axis did not change angle from the bulk of the comparative film compared to the edge, resulting in a weak spot (fracture point) at this edge. Without wishing to be bound by theory, this is believed to be caused by an anchoring effect to the Petri dish that governs the domain and cholesteric axis alignment. It is believed that when the anchoring effect to the Petri dish becomes dominant, the helical axis changes suddenly, causing fracture and creating an edge effect that leaves a sharp edge. This sharp edge is brittle and exposed, which can cause the material to further fracture, tear, and / or catch on other materials.

[0311] In contrast to the comparative film shown in FIG. 21, and referring also to FIG. 22, a scanning electron microscope image of an example of a second type of membrane 2000b is shown.

[0312] In the example of the second type of film 2000b shown in Figure 22, it can be observed that within the smallest radius of curvature, a significant fraction of the thickness at the center of gravity (greater than 0.1 times) is maintained while exhibiting smooth, non-sharp edges. The second type of film 2000b was sputter coated with 10 nm of carbon prior to SEM imaging.

[0313] Once completely dry, the membranes 2000a, 2000b may be post-treated with a heat treatment, which may or may not involve the application of pressure to the membranes 2000a, 2000b.

[0314] Once completely dried, the membranes 2000a, 2000b may be post-treated with an alkaline treatment, which may or may not involve the application of heat to the membranes 2000a, 2000b.

[0315] These membranes can be attached to a variety of substrates by a variety of means (including sewing them onto textiles to create sequin fabrics), which can be used in a variety of different industries and use cases.

[0316] It will be understood from the above discussion that the embodiments shown in the figures are merely exemplary and include features that may be generalized, eliminated, or substituted as described herein and presented in the claims. In the context of this disclosure, other examples and variations of the apparatus and methods described herein will be apparent to those skilled in the art.

[0317]

Claims

1. 1. A membrane formed from a self-assembled microstructure of anisotropic nanocrystals, the membrane having a center of gravity and a perimeter, the membrane curling back upon itself around a majority of the perimeter.

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

3. The film of claim 1 or 2, wherein the anisotropic nanocrystals comprise at least 70 wt% volume fraction of the self-assembled microstructure.

4. The film according to any one of claims 1 to 3, wherein the film is integrally formed by drying a suspension containing the anisotropic nanocrystals.

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

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

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

8. The membrane of claim 7 , wherein the one or more additives include at least one type of inorganic particle.

9. 9. The membrane of claim 7 or 8, wherein the one or more additives comprise fibers.

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

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

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

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

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

15. The membrane of claim 14 , wherein the anisotropic nanocrystals are cellulose nanocrystals.

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

17. An article comprising the membrane of any one of claims 1 to 15 bonded between a first layer and a second layer.

18. An article comprising the membrane of any one of claims 1 to 15, further comprising a coating overlying at least one surface of said membrane.

19. 20. The article of claim 18, wherein the coating encapsulates a majority of the surface of the membrane.

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

21. 1. A method of forming a film, comprising: dispensing a volume of a suspension into a mold or onto a template, the suspension comprising a suspension of anisotropic nanocrystals in a solvent; drying the dispensed suspension to form a film having a self-assembled microstructure of the anisotropic nanocrystals and having a center of gravity and a perimeter, the film curling back upon itself around a majority of the perimeter; The method comprising:

22. 1. A method of forming a film, comprising: dispensing a volume of a suspension into a mold or onto a template, the suspension comprising a suspension of anisotropic nanocrystals in a solvent; drying the dispensed suspension to form a film having a self-assembled microstructure of the anisotropic nanocrystals and having an upper surface, a lower surface, a center of gravity, and a perimeter, wherein the smallest radius of curvature around any point on the perimeter when moving from the upper surface to the lower surface is at least 0.1 times the thickness of the film at the center of gravity; The method comprising:

23. said volume of suspension is dispensed into a mould having walls with a height of 3 mm or less; 23. The method of claim 21 or 22, wherein the volume of suspension dispensed is greater than the volume contained up to the wall height of the mold.

24. 23. The method of claim 21 or 22, wherein the volume of suspension is dispensed into a mold or template formed by embossing or debossing a first substrate.

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

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

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

28. 30. The method of claim 27, wherein the one or more additives include at least one type of inorganic particle.

29. 29. The method of claim 27 or 28, wherein the one or more additives comprise fibers.

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

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

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

34. 34. The method of claim 33, wherein the anisotropic nanocrystals are cellulose nanocrystals.

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

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

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

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

39. The method of any one of claims 21 to 38, wherein the membrane is releasable from the mold or template.

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

41. 1. A method comprising: Wetting the membrane of any one of claims 1 to 15 using a second solvent; placing the membrane in contact with a surface of an object; allowing the second solvent to dry so that the film adheres to the surface of the object; and The method comprising:

42. 1. A method for making iridescent biodegradable sequins, 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 of 18°C ​​to 25°C and a relative humidity of 48% to 65% to form dried iridescent sequins; flexing the mold to release the dried iridescent biodegradable sequins from the mold; The method comprising:

43. 43. The method of claim 42, wherein the mold includes a plurality of receptacles for receiving the suspension, each receptacle including an upstanding rod for creating a hole in the sequin upon drying, the rods being made from the same material as the rest of the mold.

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

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

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

47. 47. The method of any one of claims 42 to 46, wherein the plasticizer is present in a proportion of 10% by weight of the dry mass of the cellulose nanocrystals.

48. The method of any one of claims 42 to 47, wherein the suspension further comprises a cross-linking agent.

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

50. 44. The method of claim 43, or any claim dependent thereon, wherein each receptacle is circular.

51. 44. A method according to claim 43, or any claim dependent thereon, wherein each receptacle has a diameter of 10mm and a wall height or depth of 0.3 to 0.5mm, and the rod has a diameter of 1.2mm and is 3mm from the edge and 3mm from the centre.

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

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

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

55. 55. The method of any one of claims 42 to 54, further comprising coating the iridescent sequins with a cellulosic material.

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

57. 57. A rainbow sequin made according to the method of any one of claims 42 to 56.

58. Iridescent sequins comprising cellulose nanocrystals and a plasticizer.

59. 59. The rainbow sequin of claim 58, wherein said plasticizer is sorbitol.

60. 60. The rainbow sequin of claim 58 or 59, wherein the plasticizer is at a ratio of 10% of the dry mass of the cellulose nanocrystals.

61. The rainbow sequin of any one of claims 57 to 60, further comprising a cross-linking agent.

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