Droplet Energy Harvesting Is Reverse Phenomenon of Electrowetting on Dielectric. (6th August 2021)

• Record Type: Journal Article
• Authors: Kim, Gijung; Kim, Wonjune; Chun, Honggu
• Is Part Of: Advanced functional materials. Volume 31:Number 43(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-06
• Subjects: electrowetting‐on‐dielectric -- energy harvesting -- interfacial energy -- nanoengineering; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202105233
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Electric energy is generated when water droplets slide down electrodes coated with a hydrophobic dielectric layer. The principle of energy generation needs to be clarified for the optimization and scalable design of the energy‐harvesting system. In this study, it is shown that droplet energy harvesting is the reverse phenomenon of voltage‐driven droplet actuation or electrowetting‐on‐dielectric (EWOD). For this reverse EWOD, the interfacial energy difference generated between the three‐phase contact line of the advancing and receding part of the droplet is the cause of the generation of electric energy. To prove the effect of interfacial energy on energy harvesting, the wetting property of the dielectric layer is controlled by nanopatterning while maintaining the chemical properties. The width and gap of the electrodes and the droplet size determine whether the harvested voltage waveform is monophasic or biphasic. The energy conversion efficiency is determined by the wetting properties of the surface, and the maximum value is as high as 40%. Abstract : The equation relating the harvested open‐circuit voltage with droplet contact angle based on the Young–Lippmann equation is derived and then the mechanism is experimentally verified by controlling the surface wetting property. To independently identify the effect of the interfacial energy and surface charge on energy harvesting, the surface wettability is controlled by nanopatterning on identical surface chemistry.