A direct current droplet-based triboelectric nanogenerator with a suspended probe and an exposed lower electrode

Direct current triboelectric nanogenerators (DC-TENGs) are able to facilitate both capacitor charging and operation of power-consuming devices without requiring any external rectification, thereby demonstrating significant practical potential. However, the working mechanism of droplet-based DC-TENGs remains insufficiently understood. In this study, we propose a novel direct current droplet-based triboelectric nanogenerator (DC-D-TENG) that features an air-suspended upper probe electrode. It was found that the duration of the droplet's simultaneous contact with the suspended probe and friction layer was the critical determinant of the type of power that is generated. When the electrode is suspended at a height of 2.5 mm, the device generates a stable DC output, achieving a maximum transferred charge of 32.5 nC per droplet. Remarkably, without the need for a rectifier, a 2.2 μF capacitor can be charged to 23 V within 120 s by operating 24 devices in parallel. This device can stably generate DC power output from various water sources, demonstrating the feasibility of utilizing droplet energy for electrical power generation in diverse outdoor environments and enabling direct sensing, alerting, and monitoring functions without the need for a rectifier.