Anti-swelling and photoresponsive MXene-based polyampholyte hydrogel sensors for underwater positioning and urban waterlogging pre-warning

Conductive hydrogels are viewed as the most promising materials for flexible devices. However, their applications in aquatic environments are severely limited by their inevitable swelling behavior. Herein, we report a MXene-based polyampholyte anti-swelling hydrogel possessing high stretchability (1391%), good conductivity, admirable self-healing ability (healing efficiency reached 66% after healing for 1 h), and fast photoresponsive behavior. Besides, the hydrogel-based sensor displayed a wide sensing range (2–400%) and could realize underwater monitoring and communication. More importantly, an underwater warning system was assembled, which can offer efficient real-time underwater positioning and urban waterlogging pre-warning. This work provides a new strategy for developing anti-swelling hydrogel sensors and expands their potential applications in marine exploitation and urban construction.