The skins of chameleons have attracted growing interest because they have sensitive mechano-chromic properties and bright colors due to the large surface-to-surface distances (D s−s ) between neighboring particles and contrast of the refractive index (Δn), respectively. Inspired by these, artificial mechano-chromic photonic skins (MPSs) mimicking those of chameleons were fabricated by the large Δn and D s−s . The fabrication is considerably simple and efficient based on the self-assembly strategy using commercial chemicals and materials. The reflectance of MPSs depends on the value of Δn, which can be greatly increased to 70% with a Δn of 0.035, leading to their brilliant colors. Because of the large D s−s , the MPSs possess outstanding mechano-chromic performances, including a large maximal (Δλ = 205 nm) and effective (Δλ e = 184 nm) tuning range of the reflection wavelength, high sensitivity (368), fast responsiveness (2.2 nm/ms), good stabilities (>1 year), and reversibility (>100 times). Based on these advantages, MPSs have been used for self-reporting the strain of earthworms by outputting diverse colors during the peristaltic process, indicating the great potential of the MPSs as visual sensors and optical coatings.

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 (Δn = 0) but show brilliant and tunable structural colors in other solvents due to the Δn ≠ 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.

Stimulus-responsive photonic crystals (PCs) possessing unconventional non-closely packed structures have received growing attention due to their unique capability of mimicking the active structural colors of natural organisms (for example, chameleons’...

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