Pressure‐Responsive Hierarchical Chiral Photonic Aerogels

Abstract Pressure‐responsive chiral photonic aerogels are fabricated by combining liquid crystal self‐assembly and ice‐templating processes. The aerogels have a hierarchical structure in which the primary 2D chiral nematic structured walls of cellulose nanocrystals form ribbons that support a secondary 3D cellular network. Owing to the flexibility of the aerogels in solvent, the 3D structure of the aerogel can easily be transformed to a 2D structure by pressure‐induced rearrangement. The aerogels vary from white in color, which arises from light scattering, to a reflective photonic crystal displaying bright iridescent colors that depend on the immersed solvent. A solvent‐sensitive ink that shows quick color response to different solvents is designed using the pressure‐responsive photonic aerogel. This material demonstrates a new response mechanism for the design of smart and mechanoresponsive photonic materials.