A versatile gel with shape memory capability towards strain perception and encrypted communication in underwater and low-temperature environments

Abstract

Hydrogels are potential candidate materials for developing advanced wearable flexible strain sensors. Nonetheless, due to the hydrophilicity of polymer chains and high water content, it is inevitable that hydrogels lose their inherent function in aqueous environments and under extremely low-temperature conditions, severely limiting the potential applications of hydrogel-based wearable flexible strain sensors. In this study, a multifunctional gel elastomer is successfully designed by simultaneously polymerizing isobornyl acrylate (IBOA), 2-hydroxyethyl acrylate (HEA) and acrylic acid (AA) in the presence of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) conductive additives and dimethyl sulfoxide solvents, which exhibits excellent stretchability (1134% fracture strain), long-lasting underwater stability (in water for 10 days), superior low-temperature tolerance (−40 °C), and outstanding anti-drying capability (87% mass retention after 10 days at 25 °C). Furthermore, even after being immersed in water or frozen at −40 °C for 10 days, the gel-based strain sensor can still be used for real-time tracking and monitoring of complex human and aquatic animal motion behaviors underwater or for real-time low-temperature communication using Morse code, demonstrating its excellent sensing reliability and preponderant environmental stability. Interestingly, the as-prepared gel displays attractive characteristics in terms of shape memory under external stimuli and can be used as a through-line patterned actuator to control circuit switches. These outstanding properties are expected to greatly promote the potential applications of gel-based wearable flexible electronics.