Self-Powered Sensing with Liquid-Solid Triboelectric Nanogenerators: Challenges and Opportunities.

Liquid-solid triboelectric nanogenerators (L-S TENGs) have emerged as a promising technology for sustainable energy harvesting and self-powered sensing. By leveraging interactions at liquid-solid interfaces, L-S TENGs efficiently convert low-frequency mechanical energy from various water sources─such as raindrops, waves, and flowing streams─to usable electrical energy. Compared to conventional solid-solid TENGs, L-S TENGs offer superior durability, flexibility, and cost-efficiency. Recent innovations have expanded their functionality beyond energy generation, enabling integration into self-powered sensing systems. These L-S triboelectric nanogenerator-based sensors (TENS) utilize the triboelectric output signal as an intrinsic sensing mechanism, removing external power sources and allowing fully autonomous operation. The sensing capabilities of L-S TENGs can be finely tuned by modifying the physical and chemical properties of the liquid medium or by incorporating smart materials into the solid interface. These materials can respond dynamically to external stimuli such as temperature, light, or magnetic fields, enabling an adaptive sensing performance. This perspective explores the fundamental principles, design strategies, and broad application potential of L-S TENS. It also discusses current challenges and outlines future directions for advancing these systems into multifunctional, energy-autonomous sensing platforms.