Antifreezing,\nIonically Conductive, Transparent, and\nAntidrying Carboxymethyl Chitosan Self-Healing Hydrogels as Multifunctional\nSensors

Abstract

Through a simple strategy of immersion\nin a mixed solution of water/ethylene glycol (EG)/lithium chloride\n(LiCl), self-healing carboxymethyl chitosan (CA) hydrogels, that is,\nCA/<i>N</i>-vinylpyrrolidone-EG-Li⁺ hydrogels\n(CEH) with an ultra-low-temperature freezing resistance below −70\n°C were fabricated. The introduction of electrolyte ions and\nsmall-molecule polyol also made these hydrogels highly conductive\n(0.8 S m^–1) and imparted antidrying property to\nthem, showing stable and reversible sensitivity to finger-wrist bending\nas well as 150 cycles of stretching. Such hydrogels also presented\nhighly efficient self-healing ability, with a stress–strain\nhealing efficiency of over 90%. Furthermore, the CEH-based sensors\nmaintained a stable sensing performance over a wide range of temperatures\nbelow the freezing point (from −10 to −70 °C) and\nexhibited stable sensitivity to temperatures with fast response and\nno significant hysteresis. The present work is expected to provide\na simple and sustainable route for the preparation of multifunctional\nantifreezing conductive hydrogels based on CA, leading to a wide range\nof potential applications in soft sensor devices.