Bioinspired bowl-array enabled angle-independent and fast responsive photonic colors for environmental sensing

Abstract Bioinspired adaptive coloring strategies advance the investigation of responsive photonic crystal (PC) colors for environmental visual sensing, but are being encumbered by inherent strong angle-dependent structural colors of their highly ordered photonic microstructures. Herein, imitating hexagonal pit array on the elytral surface of a male beetle- Chlorophila obscuripennis and utilizing optically isotropic features of the unique concave axisymmetric geometry, biomimetic micro-sized bowl array enabled angle-independent and flexible nano-thin PC colors are first demonstrated based on transfer printing technique which is certified as a facile, energy efficient and universal nanofabrication strategy. The photonic films assembled by functional copolymers and inorganic oxides are successfully transferred onto bowls on the surface of polydimethylsiloxane, exhibiting flexible and brilliant pixel array-like non-iridescent colors. Even after being twisted and stretched, water-washing and rubbing, the nanomaterials-based photonic films on the bowls still present glossy and stable angle-independent colors, presenting powerful strengths for practical visual sensing. In practical terms, functional copolymers based PC films on the bowls are developed as humidity and organic solvents colorimetric sensors free of angles with desirable sensitivity, remarkable durability and repeatability. And integrating photonic multilayered films with different response features, multi-mode pattern displays are realized. The remarkable sensing and display applications reflect the high values of the novel bowls enabled angle-independent photonic color building strategy.