Movement of a liquid droplet generates over 5 volts of electricity
(PHYSorg.com Nanotechnology)

Energy harvesting, a technology to transform small quantities of naturally occurring energy (e.g. light, heat and vibration) into electricity, is gaining attention as a method to power internet of things (IoT) devices. This technology helps reduce environmental impacts and has a potential to power electronic devices in a stable and long-term manner, unlike batteries that need recharging or replacing.