Using xanthan gum and PEDOT:PSS to costabilize Ga droplets to synergistically improve the toughness and sensing performance of polyacrylamide hydrogels

Conductive hydrogels have attracted tremendous attention in fabricating flexible strain sensors as highly stretchable and biocompatible strain sensing materials. However, fabricating a multifunctional conductive hydrogel simultaneously with high toughness and high sensing performance for monitoring subtle strain is still a great challenge. Herein, we developed a new conductive hydrogel by using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and xanthan gum (XG) costabilized soft Ga droplets as conductive materials and using the in situ synthesized and chemically crosslinked polyacrylamide (PAM) as the hydrogel matrix. The PEDOT:PSS simultaneously constitutes a rigid conductive network with Ga droplets, and XG constitutes a rigid sacrificial network. The Ga droplets simultaneously promote the in situ free radical synthesis and crosslinking of PAM at room temperature. The as-prepared XG-PEDOT-Ga-PAM hydrogel shows high toughness, good moldability and adhesiveness. XG-PEDOT-Ga-PAM hydrogel-based strain sensor shows a very high sensitivity (gauge factor = 12.6 in the strain range of 175%–300%), short response/recovery time (250 ms), low detection limit (<0.1%) and excellent durability (>500 cycles). The excellent sensing performance of the hydrogel-based strain sensor enabled it to be highly competent in accurately monitoring various human activities from subtle radial pulses to large-scale human joint bending.