Nature-inspired self-powered cellulose nanofibrils hydrogels with high sensitivity and mechanical adaptability

It is still a challenge to integrate high sensitivity, mechanical adaptability, and self-powered properties for hydrogels. Herein, we report a conductive polyvinyl alcohol (PVA) hydrogel based on natural nanoclay and cellulose nanofibrils (CNFs). The CNFs and PVA chains could construct a double network structure, resulting in a high mechanical composite hydrogel. Meanwhile, the nanoclay could be well dispersed and immobilized in the network of the hydrogel, thus improving mechanical adaptability of the hydrogel for curved and dynamic surfaces. Moreover, the conductive ions (Al³⁺) imparted the hydrogel with high conductivity (6.67 S m^-1) and gauge factor (1.17). Therefore, the composite hydrogel exhibited high sensitivity to tiny pressure changes, enabling recognition of the complicated sounding and handwriting. More importantly, the composite hydrogel possessed self-powered property, which could generate an output voltage of up to 78 mV. In summary, the multi-functional composite hydrogel may have giant applications in artificial electronic skins or wearable devices.