Artificial Chameleon Skins Active Mimicking Reversible Off/On Structural Colors of Insect Wings

Abstract In nature, chameleons and insect wings show characteristics of actively tunable and passively off/on structural colors, respectively, which is crucial for them to camouflage and survival. Inspired by these, photonic crystal (PC) gels possessing chameleon's nonclose‐packing structures can actively mimic the reversible off/on characteristics of the structural colors of insect wings are designed. The PC gels with outstanding tailorable, bendable, and twistable properties are prepared by nonclose‐assembling silica particles in polymers and swelling in solvents. Interestingly, the PC gels exhibit high transparency (>95%) in water because of the matching of the refractive index (Δ n = 0) but show brilliant and tunable structural colors in other solvents due to the Δ n ≠ 0. The switching between the off/on colors can be completed in tens of seconds. Based on these advantages, the PC gels are used to actively camouflage and fabricate invisible patterns that are transparent in water but revealable in other solvents. This work offers a straightforward and efficient way to build PC gels with solvents‐responsive off/on color characteristics, showing great potential in camouflage, anticounterfeiting, and optical devices.