ZnO/PDMS-Based Stretchable, Transparent, and Hydrophobic Photonic Elastomers

Inspired by the color-shifting mechanisms of chameleon skin, bionic photonic elastomers (PEs) have attracted considerable research interest, owing to their stimuli-responsive properties. However, due to the inherently low refractive index (RI) contrast, PDMS/microsphere-based PEs exhibit limitations, including weak structural color, low sensitivity, and poor mechanical repeatability. Here, we describe an easy approach for obtaining novel ZnO/PDMS PEs with tunable chromaticity in response to mechanical stimuli. The ZnO/PDMS PEs exhibit bright structural colors, high color response sensitivity, and ultrahigh repeatability. Due to the thin thickness (1.7 μm) and the relatively high refractive index of the ZnO photonic crystal, the generated structural color of ZnO/PDMS PE can change from red to cyan at just a ε = 40% strain, and the reflection wavelength shifted from 655 to 502 nm correspondingly (mechanochromic sensitivity: 3.8 nm·%–1). Importantly, this mechanochromic PE exhibits a reversible response to external mechanical stimuli over 10,000 cycles because the structural color can change dramatically at small ε. Furthermore, the submicrometer ZnO structure also brings high hydrophobicity during stretching (θ > 120°) and high transmittance in the visible region (T > 80%) to the PEs. Such a multifunctional colorful elastomer provides new ideas for the design of bionic skin.