The global energy crisis facing us today is on the rise. At the large scale, the increasing threat of energy crisis as well as global warming is pushing people to actively search for low-cost, sustainable approaches to harvest energy with improved performances. At the small scale, as we enter a new era of intelligence, people are constructing a huge number of objects linked to the “Internet of Things” to continuously track and monitor the real-time status and data of various objects. In such applications, the devices to be powered are widely distributed, and the power needed is at the scale of microwatt to watt range. New techniques that can harvest clean and renewable energy resources, at a myriad of scales, are in urgent need.

Recently, several water energy-harvesting techniques that rely on the generation and transfer of interfacial charges have drawn significant attention, such as triboelectric nanogenerator (TENG), reverse electrodialysis, and hydrovoltaic technology. Operating in various working conditions, the performances of these devices are closely dictated by the interfacial properties of dielectric materials as well as their interaction with liquid. In particular, a slippery surface that allows for timely shedding of liquid is important for continuous water kinetic energy harvesting. Moreover, most water energy-harvesting devices to date are limited by low energy density owing to the fact that the generation and transfer of interfacial charges mainly occur at the interface, which is an interfacial effect by nature.