A Flexible and Robust Structural Color Film Obtained by Assembly of Surface-Modified Melanin Particles

Abstract

In this study, core–shell-hairy-type melanin particles surface modified with a polydopamine shell layer and a polymer brush hairy layer were fabricated and assembled to readily obtain bright structural color films. The hot pressing of freeze-dried samples of melanin particles decorated with a hydrophilic, low glass transition temperature polymer brush results in films that exhibit an angle-dependent structural color due to a highly periodic microstructure, with increased regularity in the arrangement of the particle array due to the fluidity of the particles. Flexible, self-supporting, and easy-to-cut and process structural color films are obtained, and their flexibility and robustness are demonstrated using compression tests. This method of obtaining highly visible structural color films using melanin particles as a single component will have a significant impact on practical materials and applications.

Influences of Heat Treatment, Particle Arrangement, and Binder Addition on the Mechanical Robustness of Structurally Colored Coatings Formed with Monodisperse SiO2 Spheres

“…Recently, several strategies have been reported for improving the mechanical robustness of particle-array-type structurally colored materials. [25][26][27][28][29] The addition of polymers-such as poly(vinyl alcohol), [25] polyacrylate, [26,28] and polydopamine [29][30][31] -as binders is a typical approach to enhance the mechanical durability of particle arrays. For example, Xing et al demonstrated that structurally colored fabrics prepared using polydopamine-coated spheres have bright structural colors, strong mechanical robustness, and can withstand soaking, laundering, folding, and abrasion testing.…”

Photonic Crystal Films Based on Polymer Particles with a Core/Shell Structure Responding to Ethanol

“…Photonic crystals (PCs) are a class of materials that are promising both for studying new fundamental phenomena in quantum and nonlinear optics and for creating hierarchical materials with new physical, physicochemical, or biological properties. − The fundamental property of PCs is a spatially periodic change of its permittivity with a period comparable to the light wavelength. − Since the reflection wavelength of a polymer film based on PCs can be easily varied by changing the diameter of monodisperse polymer particles, − it is possible to create optical sensor materials based on polymeric PCs. Also, the reflection wavelength of the PC-based film can be modulated by changing the lattice spacing due to external influences, such as temperature, pressure, and the presence of volatile organic compounds. − PCs with tunable optical properties have great potential for a wide range of applications such as strain sensors or smart labels. − …”

Crack-Free Structural Color Materials Prepared without Disrupting the Particle Arrangement by Controlling the Internal Stress Relaxation and Interactions of the Melanin Particles

“…Based on the coloration mechanisms of vivid organisms involving microstructures formed by melanin, a biopolymer that absorbs visible light, , we conducted a series of studies on biomimetic structural color materials containing polydopamine (PDA), a melanin-mimetic substance. , Due to incoherent multiple scattering, conventional materials produce whitish structural colors and low saturation. On the other hand, melanin particles, i.e., PSt@PDA core–shell particles with PDA coated on the surfaces of monodisperse polystyrene (PSt) particles, produce a variety of highly visible structural colors depending on their sizes, shapes, and compositions. − Coating the particle surface with PDA can absorb light in the visible region and suppress diffuse reflection, thereby improving structural color contrast, which can be achieved using carbon-based materials as well . The use of melanin particles as building blocks is an effective way to produce vivid structural color materials. , Thus, developing crack-free melanin-based structural color materials remains an attractive challenge for practical application.…”