Liquid-Metal-Based Stretchable Triboelectric Nanogenerators for Flowing-Liquid-Based Energy Harvesting and Self-Powered Sensor Applications

In this paper, a liquid-metal-based triboelectric nanogenerator (LM-TENG) is proposed for harvesting energy from flowing water and self-powered flow sensor applications. The proposed LM-TENG mainly consists of a Galinstan working electrode that is encapsulated in a polydimethylsiloxane friction layer. The triboelectric performance of the LM-TENG is optimized as a function of flow rate and frictional layer thickness. The output performance of the optimized LM-TENG (6.2 V and 3.6 µA) is superior to that of the copper-electrode-based TENG (C-TENG, 2.4 V and 0.8 µA) at the flow rate of 2.5 L min⁻¹. This is because the stretchability of the optimized LM-TENG is three times higher than that of the C-TENG, which increases the contact area and enhances the output performance. The optimized LM-TENG is successfully demonstrated as a self-powered flow sensor for remote monitoring of water flow in pipelines. In addition, the LM-TENG is a capable of powering more than 30 LEDs and directly powering low-power electronics (LCDs).