A mechanically strong and highly conductive MXene/polyacrylamide–alginate composite hydrogel with a double-network structure for a flexible wearable sensor

Abstract

Flexible wearable sensors have attracted considerable attention in the applications of biomedicine, human–computer interaction, and many other fields. Flexible hydrogel-based wearable sensors stand out because of their excellent flexibility and biocompatibility for monitoring human activities. However, the existing hydrogel-based sensors are generally faced with bottlenecks such as low mechanical strength, poor sensing stability (or repeatability), and limited sensitivity, which greatly hinders their practical applications. Herein, a novel mechanically strong and highly conductive double-network MXene-sodium alginate (SA)-polyacrylamide (PAM)-Ca²⁺/Li⁺ (MSP-Ca²⁺/Li⁺) composite hydrogel with MXene (Ti₃C₂T_x) nanosheets and lithium chloride (LiCl) as conductive fillers is developed for enhancing ionic conductivity. The results show that the M3S1P3-Ca²⁺/Li⁺ composite hydrogel exhibits high compression and tensile properties as well as good stretchability and elasticity, and fast self-recoverability which are mainly caused by the synergistic effect of the nanofiller and chemical and physical co-crosslinking. The M3S1P3-Ca²⁺/Li⁺ composite hydrogel sensor could maintain a stable and reversible electrical resistance signal output under standard cyclic tensile strain sensing persisting around 3600 s with a high gauge factor (GF) of 1.45 and a low latency of 60 ms. Specifically, under realistic human motion monitoring tests (i.e., finger, arm, wrist, and mouth motions), the sensor exhibited excellent sensing sensitivity and repeatability without reduction in the mechanical and electrical properties. Therefore, the MSP composite hydrogel could provide a simple solution for the realization of intelligent multi-functional physiological detection and also will pave the way for the new generation of biomimetic skin-like sensors.