Bionic Structural Coloration of Textiles Using the Synthetically Prepared Liquid Photonic Crystals.

The structural coloration of textiles with bionic photonic crystals (PCs) is expected to become a critical approach to the ecological coloration of textiles. Rapid and large-area preparation of PC structurally colored textiles can be achieved via self-assembly of high mass fractions of liquid photonic crystals (LPCs). However, the rapid and large-scale manufacturing of LPCs remains a challenge. In this work, the pH regulator is added in the process of emulsion polymerization to solve the problem of phase transformation caused by the thermal decomposition of the initiator to produce H+ , directly achieving 40 wt.% PS nanospheres in the dispersion. Then oligomers and small-molecule salts are removed from the system via dialysis, and the pre-crystallized LPC system is efficiently prepared. Adjusting the particle size and the mass fraction of nanospheres is shown to be an efficient way to control the optical properties of LPCs. The rapid and large-area preparation of PC structural color fabric and the patterned PC structural color fabric with an iridescent effect is implemented by using LPCs as the assembly intermediate. By constructing the encapsulation layer on the surface of the PC structural color fabric, the consistency of high structural stability and high color saturation of the PC is realized.

Patterned SiO2/Polyurethane Acrylate Inverse Opal Photonic Crystals with High Color Saturation and Tough Mechanical Strength.

Patterned structural color photonic crystals (PCs) based on periodic photonic nanostructures have attracted great interest in developing high-performance sensors and other smart optical materials as well as tunable structurally colored fashion textiles. However, previously reported patterned PCs with both high color saturation and tough mechanical strength were difficult to achieve, which restricts their practical applications. Herein, arbitrarily patterned silica/polyurethane acrylate (SiO2/PUA) inverse opal photonic crystals (IOPCs) with high color saturation and tough mechanical strength were innovatively designed and fabricated by writing with photopolymerizable PUA "ink" on a self-assembled hollow SiO2 PC template. The high color saturation of the prepared SiO2/PUA IOPCs originated from the high refractive index contrast between the encapsulated air-filled core and the SiO2/PUA composite skeleton. The cross-linked flexible PUA matrix tightly warped the self-assembled hollow SiO2 nanospheres together, endowing the obtained SiO2/PUA IOPCs a structural color pattern with tough mechanical strength. The structural colors of SiO2/PUA IOPCs could be finely tuned by regulating their basic parameters, and a redshift in the resultant structural color was observed due to an increase in the lattice constant when increasing the core size and/or shell thickness of the hollow SiO2 nanospheres.

Preparation of Patterned Photonic Crystals with High Fastness and Iridescence Effect via Resist-Screen Printing.

Patterned photonic crystals (PCs) have great application potential in the textile field owing to their attractive high-saturation iridescent effect. Herein, based on the idea of resist printing, a novel approach to constructing patterned photonic crystals via screen printing was designed and achieved. A colorless pattern with hydrophilic and hydrophobic difference was firstly prepared by screen printing using a hydrophilic polymer paste printed on a hydrophobic fabric, and then the PC structurally colored pattern was obtained through scrapping liquid photonic crystals (LPCs) on the fabric because the LPCs were spread and assembled in the hydrophilic pattern but resisted in the hydrophobic areas, so that to realize the rapid preparation of patterned PCs on the fabric surface. Once the contact angle difference (ΔCA) between the hydrophilic and hydrophobic areas exceeded 80, the "color paste" (that is, LPCs) did not stain the hydrophobic area at all after scrapping, and the assembled PCs pattern showed good contour sharpness and high-saturation iridescence effect. The complex multistructural color patterns on the fabrics were achieved by adjusting the size of nanospheres and using multistep printing and scrapping. The preparation of the protective layer on the PC surface effectively improved the structural stability of the patterned PCs while retaining the optical properties of the pattern. This patterned PCs preparation method was combined with a conventional responsive substance (rhodamine B) to obtain double anti-counterfeiting patterned PCs with the iridescence effect. The results suggested a promising future in both the highly efficient preparation of patterned PCs and the application of PCs in the anti-counterfeiting field.

High Structural Stability of Photonic Crystals on Textile Substrates, Prepared via a Surface-Supported Curing Strategy.

Over the past years, photonic crystals (PCs) with a periodically ordered nanostructure have attracted great attention due to their potential as advanced optical materials for structural coloration of textiles. However, the weak structural stability of PCs on flexible textile substrates makes them vulnerable to strong external forces, hampering their large-scale application. In this work, a waterborne polyurethane (wPU) is chosen for enhancing the structural stability of PCs. The composite PCs (PCs/wPU) show both brilliant structural colors and significantly improved structural stability. The structural color produced by the encapsulated PCs is found to depend on the properties of encapsulating agents. The wPU with high surface tension solidifies mainly on the PC surface in the form of a transparent film, protecting the overall structure of PCs. Meanwhile, a small amount of wPU, infiltrating into the interior of PCs, provides strong adhesion and ensures stability among nanospheres. In turn, polydimethylsiloxane (PDMS) with low surface tension is easy to infiltrate into the interior of PCs, forming fully encapsulated PCs. This reduces the brightness of structural color produced by the final PCs/PDMS composite over the original PCs, due to the replacement of air by PDMS, and thus the decrease in the refractive index contrast of PCs. The supported curing strategy using the encapsulating agent with high surface tension is shown to not only improve the structural stability of PCs but also exert almost no influence on the optical properties of PCs, facilitating the practice application of structural coloration in the textile industry.

Facile Fabrication of Amorphous Photonic Structures with Non-Iridescent and Highly-Stable Structural Color on Textile Substrates.

Amorphous photonic structures with non-iridescent and highly-stable structural color were fabricated via a simple one-step spray-coating technique. With this strategy, the obtained films on textile substrates presented short-ordered and amorphous photonic structures (APSs) similar to the amorphous nanostructures of avian feathers. The structural color presented the same hue when viewed at different angles and could be well controlled by varying the diameters of the SiO2 nanospheres. The prepared fabrics with structural color exhibited high color stability due to stability in both the assembled physical structure and the refractive index. The high stability of the assembled physical structure was attributed to the cementing effect of Poly(methylmethacrylate-butylacrylate) P(MMA-BA) existing between textile substrate and SiO2 nanospheres and among SiO2 nanospheres, while the high stability in the refractive index was contributed by the liquid-resistance achieved by both the surface roughness and the low-surface-energy of the as-sprayed APSs. With the resistances to external forces and liquid invasion, the non-iridescent brilliant structural color of the as-prepared fabrics could be kept steady. In this study, an approach of fabricating APSs with non-iridescent and stable structural color was established to enhance its potential application in structural coloration of textiles, and other color-related smart textiles. .