Light up 100 LEDs with a drop of water

A TEAM led by scientists from the City University of Hong Kong has developed a droplet-based electricity generator, featured with a field-effect transistor -like structure that allows for high energy-conversion efficiency and instantaneous power density increased by thousands of times compared with its counterparts without an FET-like structure. However, the amount of charges generated on the surface is limited by the interfacial effect, and as a result, the energy conversion efficiency is quite low. First, the team found that droplets continuously impinging on the surface of polytetrafluoroethylene, an electret material with a quasi-permanent electric charge, provided a new route for the accumulation and storage of high-density surface charges. When a falling water droplet hits and spreads on the PTFE/ITO surface, it “bridges” the aluminium electrode and the PTFE/ITO electrode, translating the original system into a closed-loop electric circuit.