Synthesis of Self-Adhesive, Self-Healing and Antifreeze Conductive Hydrogels for Flexible Strain sensors

 Recently, significant progress has been made regarding conductive hydrogels-based flexible sensors in health detection, electronic skin, soft robots, etc. However, the requirement of bonding with the substrate through the adhesive tape, brokenness sensitivity, and degradation of performance under low-temperature environments, strongly limit the wide applications of conductive hydrogels in flexible sensors. To solve these problems, this study introduces lithium chloride (LiCl) into poly(vinyl alcohol)/tannic acid/polyacrylamide (PVA/TA/PAM) hydrogels to endow the hydrogels with excellent conductivity and antifreeze properties. In addition, the addition of tannic acid (TA) and zwitterionic 3-[Dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azaniumyl]propane-1-sulfonate (SBMA) enables the hydrogel to have good self-healing performance (after 72 h of healing at 20 °C, the healing efficiency of fracture stress is 24%, and the healing efficiency of fracture strain is 52%) and adhesion (the adhesion strength to paper at 20 °C is 14.12 KPa). The sensors based on PVA/TA/PAM composite hydrogels exhibit good sensibility, stability, and durability, and can respond quickly to human joint activities (finger bending, wrist bending, arm bending, and leg bending). Therefore, the multifunctional PVA/TA/PAM composite hydrogel demonstrates significant potential for applications in flexible strain sensors under extreme environments.