Stretchable, adhesive and conductive cellulose nanofiber-based hydrogel for multifunctional wearable electronics

Conductive hydrogels have shown significant potential in wearable sensors and energy harvesting due to their distinctive conductive network and excellent flexibility. In this work, a conductive CNF/PAM/PANI (CPP) hydrogel with excellent performance as wearable sensors and supercapacitor was successfully prepared by free radical polymerization, multiple hydrogen bonding and the combination of ionic/electronic dual-conductive network. The incorporation of Li⁺ has modulated the interaction between the cross-linked networks, endowing the hydrogel with excellent tensile properties (1200 %) and high tensile strength (119 kPa). The synergistic effect of Li⁺ ion conduction sites and the polyaniline conjugated π-electron system has greatly enhanced the conductivity. This ionic/electronic dual-conductive hydrogel exhibited high sensitivity to tensile and compressive stress, thus the as-fabricated sensors possessed a high sensitivity (GF = 8.95), fast response and recovery time (250 ms and 200 ms) and a wide sensing range (400 %). In addition, the triboelectric nanogenerator based on the CPP conductive hydrogel system has a maximum power density of 69 mW/m², enabling energy harvesting from human movements to power small devices and monitor joint movements. The flexible supercapacitor with CPP hydrogel as the electrolyte showed a high specific capacitance of 309.41 mF/cm² at a scanning speed of 0.5 mA/cm², and the capacitance retention rate during charging and discharging at -20 °C was still 77 %. This novel ionic/electronic dual-conductive hydrogel offers new opportunities for developing wearable electronics and energy harvesting systems.