Floating droplet electricity generator on water.

Hydrovoltaic technology holds great potential for energy harvesting from the natural water cycle. In this work, we present a novel water-integrated floating droplet electricity generator adopting a top electrode-dielectric-water architecture, where natural water acts as both the bottom electrode and substrate. The generator achieves high electrical output, comparable to the conventional counterpart using a metal bottom electrode and rigid substrate, while demonstrating 87% material weight reduction and 50% cost saving, as well as great durability in varying working environments. Its operational principle leverages the incompressibility and high surface tension of water to support the dielectric layer under droplet impinging and spreading, and the ion-rich composition of water enables exceptional high-frequency conductivity as the bottom electrode. The high surface tension of water also realizes unidirectional water transport for self-regulated water drainage. The advantages of water integration are further substantiated by the outstanding scalability, which is manifested by a sub-square-meter integrated device (∼0.3 m²). We anticipate this work will open up a new avenue of harnessing water-like natural materials to construct hydrovoltaic devices and advance land-free large-scale applications.