Mechanochromic and Conductive Chiral Nematic Nanostructured Film for Bioinspired Ionic Skins

Chameleon skin is naturally adaptive and can sense environmental changes and transform sensing into bioelectrical and optical signals by manipulating ion transduction and photonic nanostructures. The increasing interest in mimicking biological skins has considerably promoted the development of advanced photonic materials with an increasing ionic conductivity. Herein, we report the judicious design and fabrication of a bioinspired mechanochromic chiral nematic nanostructured film with good ionic conductivity by infiltrating fluorine-rich ionic liquids (FILs) into a swollen self-assembled cellulose nanocrystal (CNC) film with helical nanoarchitectures. Notably, the introduction of 2-hydroxyethyl acrylate considerably enhances the compatibility of hydrophobic FILs and hydrophilic CNCs. The resulting FIL-CNC nanostructured films exhibited excellent mechanochromism, good ionic conductivity, and outstanding optical/electrical dual-signal sensing performance when used as a bioinspired ionic skin for real-time monitoring of human motions. Owing to the integration of FILs, the underwater stability of the chiral liquid crystal nanostructures of CNCs was significantly enhanced. Notably, underwater contact/contactless sensing modes and encrypted information transmission have been achieved with the FIL-CNC nanostructured film. This study can offer great insights for the advancement of biomimetic multifunctional artificial skins and emerging interactive devices, which can find important applications in wearable iontronics, human-machine interactions, and intelligent robots.