Anti-freezing and conductive hydrogel with water-resistant properties for flexible underwater sensors

Flexible strain sensors based on hydrogels have numerous application prospects. However, the high water content and unsatisfactory water resistance of traditional hydrogel-based sensors limits its application in harsh environment, such as subzero environment and underwater environment. Herein, conductive poly(acrylamide-co-2-hydroxyethyl methacrylate) ionic glycerol-hydrogel was developed through the hydrophobic aggregation interaction and double cross-linking network. The resultant ionic glycerol-hydrogel exhibited excellent anti-freezing properties (-34 °C), water-resistant properties (swelling ratio less than 3 %), ionic conductivity (0.7 S m−1), and strain sensing capabilities (Gauge factor up 1.73). The flexible strain sensors based on ionic glycerol-hydrogel could detect electrical signals at subzero temperatures. Moreover, the hydrogel sensors achieved effective detection and discrimination of Morse codes to transmit underwater information. Demonstrated its potential application in wearable devices.