Superelastic,\nAntifreezing, Antidrying, and Conductive\nOrganohydrogels for Wearable Strain Sensors

Abstract

Sensors\nbased on conductive hydrogels have received extensive attention\nin various fields, such as artificial intelligence, electronic skin,\nand health monitoring. However, the poor resilience and fatigue resistance,\nicing, and water loss of traditional hydrogels greatly limit their\napplication. Herein, an ionic conductive organohydrogel (PAC-Zn) was\nprepared for the first time by copolymerization of cardanol and acrylic\nacid in water/1,3-butanediol as a binary solvent system. A very small\namount of cardanol (1% cardanol of total monomers) could not only\nsignificantly improve the tensile strength (∼4 times) and toughness\n(∼3 times) of PAA but also improve its extensibility. Due to\nthe presence of 1,3-butanediol, PAC-Zn showed outstanding tolerance\nfor freezing (−45 °C) and drying (over 85% moisture retention\nafter 15 days of storage in a 37 °C oven). Compared with ethylene\nglycol and glycerol as antifreeze agents used in organohydrogels,\nthe addition of 1,3-butanediol endowed the organohydrogel with not\nonly similar frost resistance but also better mechanical performance.\nBesides, PAC-Zn exhibited fast resilience (almost no hysteresis loop)\nand excellent antifatigue ability. More importantly, a PAC-Zn organohydrogel-based\nsensor could detect human motion in real time (wrist, elbow, finger,\nand knee joints), revealing its fast response, good sensitivity, and\nstable electromechanical repeatability. In conclusion, the multifunctional\nPAC-Zn organohydrogel is expected to become a potential and promising\ncandidate in the field of strain sensors under a broad range of environmental\ntemperatures.