Superhydrophobic, Anti-Freezing and Multi-Cross-Linked Wearable Hydrogel Strain Sensor for Underwater Gesture Recognition.

Conductive hydrogel is considered to be one of the most potential sensing materials for wearable strain sensors. However, both the hydrophilicity of polymer chains and high water content severely inhibit the potential applications of hydrogel-based sensors in extreme conditions. In this study, a multicross-linked hydrogel was prepared by simultaneously introducing a double-network matrix, multiple conductive fillers, and free-moving ions, which can withstand an ultralow temperature below -80 °C. A superhydrophobic Ecoflex layer with a water contact angle of 159.1° was coated on the hydrogel using simple spraying and laser engraving methods. Additionally, the smart glove integrating five hydrogel strain sensors with a microprocessor was developed to recognize 12 types of diving gestures and synchronously transmit recognition results to smartphones. The superhydrophobic and antifreezing hydrogel strain sensor proposed in this study emerges promising potentials in wearable electronics, human-machine interfaces, and underwater applications.