Switchable and Tunable Chemical/Structure Color in a Flexible Hierarchical Surface

Cephalopod skin is capable of fast color changing enabled by tunable skin transparency as well as structure color. Under this inspiration, herein, a flexible surface with unique hierarchical structure that integrates both transparency change in chemical color (optical scattering) and structure coloration (optical interfering) is developed by harnessing wrinkling instability, thanks to the interfacial Au catalysis in soft lithography. As a result, a hierarchical structure in terms of wrinkled film overlaid by nano-dome array is obtained in the flexile surface. Experiments find that subject to biaxial strains from 0% to 60%, the hierarchical surface first experiences a transition from nontransparent to transparent owing to the flattening of the wrinkles and then exhibits iridescence structure color shifting from blue to red. The switchable and dynamical tunable mechanochromic characteristics are demonstrated in a smart window, offering potentials for developing flexible devices with optical multiple functionality.