Antifreezing, Ionically Conductive, Transparent, and Antidrying Carboxymethyl Chitosan Self-Healing Hydrogels as Multifunctional Sensors

Through a simple strategy of immersion in a mixed solution of water/ethylene glycol (EG)/lithium chloride (LiCl), self-healing carboxymethyl chitosan (CA) hydrogels, that is, CA/N-vinylpyrrolidone-EG-Li+ hydrogels (CEH) with an ultra-low-temperature freezing resistance below −70 °C were fabricated. The introduction of electrolyte ions and small-molecule polyol also made these hydrogels highly conductive (0.8 S m–1) and imparted antidrying property to them, showing stable and reversible sensitivity to finger-wrist bending as well as 150 cycles of stretching. Such hydrogels also presented highly efficient self-healing ability, with a stress–strain healing efficiency of over 90%. Furthermore, the CEH-based sensors maintained a stable sensing performance over a wide range of temperatures below the freezing point (from −10 to −70 °C) and exhibited stable sensitivity to temperatures with fast response and no significant hysteresis. The present work is expected to provide a simple and sustainable route for the preparation of multifunctional antifreezing conductive hydrogels based on CA, leading to a wide range of potential applications in soft sensor devices.