Self-powered green energy-harvesting and sensing interfaces based on hygroscopic gel and water-locking effects.

The rapid proliferation of flexible electronics necessitates the development of self-powered energy harvesting systems with continuous power output and sensing signal monitoring. In this study, inspired by transient voltage output (0.2 volts, <1 hour) through dipping water droplets on metal oxide substrates, a self-sustained energy harvesting and sensing interface (SEHSI, 0.32 volts, >4 days) is proposed by replacing movable water droplets with "confined" moisture, harvested and locked by a hygroscopic polymeric gel with high sorption capacity and rapid sorption-desorption kinetics. Further analysis reveals the capacitive behavior of SEHSI, leading to excellent tactile sensing capabilities with high sensitivity and rapid responsiveness, and humidity and temperature response with robust cyclic stability for over 10,000 cycles. Such all-in-one powering and sensing platforms demonstrate promising application potential in self-powered human-machine interactions, including breath status monitoring, contactless motion detection, and braille detection. Our design establishes a promising approach to developing self-powered energy harvesting and sensing systems for human-machine interfaces.