A Dual‐Mode Triboelectric Nanogenerator for Efficiently Harvesting Droplet Energy

Abstract Triboelectric nanogenerator (TENG) is a promising solution to harvest the low‐frequency, low‐actuation‐force, and high‐entropy droplet energy. Conventional attempts mainly focus on maximizing electrostatic energy harvest on the liquid‐solid surface, but enormous kinetic energy of droplet hitting the substrate is directly dissipated, limiting the output performance. Here, a dual‐mode TENG (DM‐TENG) is proposed to efficiently harvest both electrostatic energy at liquid‐solid surface from a droplet TENG (D‐TENG) and elastic potential energy of the vibrated cantilever from a contact‐separation TENG (CS‐TENG). Triggered by small droplets, the flexible cantilever beam, rather than conventional stiff ones, can easily vibrate multiple times with large amplitude, enabling frequency multiplication of CS‐TENG and producing amplified output charges. Combining with the top electrode design to sufficiently utilize charges at liquid‐solid interface, a record‐high output charge of 158 nC is realized by single droplet. The energy conversion efficiency of DM‐TENG is 2.66‐fold of D‐TENG. An array system with the specially designed power management circuit is also demonstrated for building self‐powered system, offering promising applications for efficiently harvesting raindrop energy.