Superelastic, Antifreezing, Antidrying, and Conductive Organohydrogels for Wearable Strain Sensors

Abstract

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