Water droplet-driven triboelectric nanogenerator with superhydrophobic surfaces

A bouncing water droplet not only contains mechanical energy, but also electrostatic energy due to the triboelectric charges on its surface that are generated by its contacts with the surrounding environment. Here, we report development of contact electrification-based water droplet-driven triboelectric nanogenerator (Wd-TENG) for harvesting energy from the water-droplet bouncing between two superhydrophobic surfaces. The Wd-TENG consists of polytetrafluoroethylene balls on the bottom and zinc oxide nanosheets on the top; two surfaces of the device obtain electric energy during the contact electrification from the bouncing water, and additionally, maximize the bouncing motions of the droplets. The device produced a short-circuit current and an open-circuit voltage of 1.3 μA and 1.4 V, respectively. Besides, power-generating performances of the Wd-TENG at various angles of inclination were also investigated, and it showed voltage outputs of 5.5 V, 16 V, 9.8 V, and 6.8 V at the inclination angles of 52°, 58°, 64°, and 70°, respectively. These results demonstrate that the Wd-TENG is potentially a strong candidate for scavenging energy from raindrops.