Broadband and pixelated camouflage in inflating chiral nematic liquid crystalline elastomers

Living organisms such as fishes1, cephalopods2 and clams3 are cryptically coloured with a wide range of hues and patterns for camouflage, signalling or energy regulation. Despite extensive efforts to create colour-changing materials and devices4, it is challenging to achieve pixelated structural coloration with broadband spectral shifts in a compact space. Here, we describe pneumatically inflating thin membranes of main-chain chiral nematic liquid crystalline elastomers that have such properties. By taking advantage of the large elasticity anisotropy and Poisson’s ratio (>0.5) of these materials, we geometrically program the size and the layout of the encapsulated air channels to achieve colour shifting from near-infrared to ultraviolet wavelengths with less than 20% equi-biaxial transverse strain. Each channel can be individually controlled as a colour ‘pixel’ to match with surroundings, whether periodically or irregularly patterned. These soft materials may find uses in distinct applications such as cryptography, adaptive optics and soft robotics. Pneumatically actuated membranes made from a chiral nematic liquid crystalline elastomer supported by poly(dimethylsiloxane) layers are assembled into pixelated colour devices, where each individual pixel can be tuned throughout the entire visible spectrum.