Droplet Energy Harvesting Is Reverse Phenomenon of Electrowetting on Dielectric

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%.

Recent advances in solid–liquid triboelectric nanogenerator technologies, affecting factors, and applications

“…The S–L triboelectric nanogeneration by 80 μL droplets and the dielectric layer can drive motion of 1-μL droplets. In 107 , parameters including the slipping speed of droplets in the slipping process and the front and rear contact angles, and the energy harvesting efficiency of the entire system are discussed from perspectives of electrowetting and reverse electrowetting.…”

Electrically Mediated Static Contact Angle and Hysteresis of Polyelectrolyte Solutions

“…Electrowetting-on-dielectric (EWOD) has attracted significant research interest due to several features, such as rapid response, real-time actuation, long-term reliability, and very high stability. A variety of technological applications have been derived from EWOD, including variable focal lenses, direct ink writing (DIW), − spray painting and coating, − electrical-based DIW, − energy harvesting, , electronic paper, diagnostic chip, , biochemical detection, and microreactors, among others. In a classical electrowetting system, a solid electrode is coated with a hydrophobic dielectric layer − (see Figure ).…”

Robust reverse-electrowetting based energy harvesting on slippery surface

“…[17][18][19] As a solid/liquid capacitive power generation device with bias voltage, the performance of REWOD-DEG is limited by wetting behavior and the inherent charge trapping and dielectric failures of the electrowetting system. [18][19][20] Up to date, oil infused slippery surface has been introduced in variety EWOD or droplets energy harvesting applications, [21][22][23][24] its unique advantages given by the uidic nature, such as low contact angle hysteresis, antifouling, self-healing and liquid repellency have been extensively studied. However, the dielectric properties of SLIPS lm as a liquid dielectric layer was rarely reported.…”

“…Among them, reversed-electrowetting based droplet electricity generator (REWOD-DEG) shows great advantages in high power densities (up to 10 3 W m −2 ), tunable output formats (several volts to tens of volts), and wide adaptability to diverse mechanical energies, such as energy harvesting from human movement and high-power generation from mechanical vibration, which supports promising application in portable, wearable devices. 17–19…”

“…Among them, reversed-electrowetting based droplet electricity generator (REWOD-DEG) shows great advantages in high power densities (up to 10 3 W m −2 ), tunable output formats (several volts to tens of volts), and wide adaptability to diverse mechanical energies, such as energy harvesting from human movement and high-power generation from mechanical vibration, which supports promising application in portable, wearable devices. [17][18][19] As a solid/liquid capacitive power generation device with bias voltage, the performance of REWOD-DEG is limited by wetting behavior and the inherent charge trapping and dielectric failures of the electrowetting system. [18][19][20] Up to date, oil infused slippery surface has been introduced in variety EWOD or droplets energy harvesting applications, [21][22][23][24] its unique advantages given by the uidic nature, such as low contact angle hysteresis, antifouling, self-healing and liquid repellency have been extensively studied.…”