Droplet-Based Triboelectric Nanogenerators with Needle Electrodes for Efficient Water Energy Harvesting

With the advent of droplet-based triboelectric nanogenerators (D-TENGs), methods for converting raindrop kinetic energy to electrical energy have developed rapidly. However, current D-TENG designs suffer from slow solid-liquid interface separation speeds and susceptibility to liquid residues. These issues compromise the output performance of D-TENGs and limit their applications in high-power electrical appliances. To address this, this study presents a needle electrode droplet-based triboelectric nanogenerator (NED-TENG). The needle electrode functions as the top electrode, optimizing solid-liquid contacts and efficiently harvesting raindrop kinetic energy by leveraging the triboelectric and electrostatic induction mechanisms. This needle electrode is made from one end of a copper wire, with its other end directly connected to the energy harvester. This setup positions all of the wiring on the back of the substrate, accelerating liquid separation, mitigating residue formation, and simplifying device fabrication. Upon assembly of the device, several factors influencing the performance of the fabricated D-TENG and its action mechanisms are explored to improve its output efficiency. Experimental results reveal that the designed D-TENG only requires 6 s to saturate the surface charge of its polytetrafluoroethylene film, achieving a short-circuit current (I_SC) of up to 4.76 mA and an output voltage (V₀) of up to 563 V. Overall, this study offers a straightforward and effective approach for harvesting kinetic energy from rainwater.