Mechanochromic and Conductive Gels Based on Cellulose Nanocrystals for Bioinspired Sensing

Soft mechanochromatic materials hold great promise for wearable sensing technologies. Bioinspired photonic crystal structures assembled from cellulose nanocrystals (CNCs) enable dynamic light modulation, providing a vibrant and easily controlled optical platform for real-time detection. This study constructed a CNC-based mechanochromic and conductive gel with a dual-signal response featuring interactive optical and electrical feedback. The mechanical response is achieved through the integration of encapsulating, interpenetration, and crystallization of a soft biocompatible poly(vinyl alcohol) (PVA) sandwich matrix, which propels the deformation of the encased CNC photonic crystal core, leading to dynamic changes in conductivity and color. The material exhibits the capability of detecting dynamic tensile/compressive strains (up to 130%/49% along with a visually discernible color shifting from red to blue) and recognizing finger bending and specific spoken words, which showcases its potential in pliable dual-signal sensing in human health monitoring and strain detection.