Abstract

Many industrial technologies, such as condensation cooling and fuel cells, require solid-liquid separation. Electrowetting is a very effective method of inducing droplets to detach from hydrophobic surfaces, and it is very convenient to control. The jumping of droplets excited by an electric field depends on the conversion of surface energy into kinetic energy and other forms of energy. At present, there is still a lack of in-depth research on this process. In this study, a high-speed camera is used to capture the jumping motion of a droplet on a hydrophobic surface under the actuation of electrowetting, and the threshold voltage that causes the droplet to detach is estimated based on the changes in contact angle and droplet shape. A self-written Matlab program is used to analyze and calculate the various forms of energy in the process of droplets detaching and subsequent bouncing. The results show that there is an obvious coupling relationship between the kinetic energy and potential energy of the droplet’s center of mass during the flight of the droplet from the surface. The vibrational kinetic energy and surface potential energy also show a certain coupling relationship during the flight phase. The internal dissipation caused by the viscosity of the droplet increases with the droplet oscillation amplitude increasing, and decays with time. Because it can cause the droplet to oscillate and deform and create more surface energy, AC pulses are more efficient than direct current in the droplet bounce. By revealing the energy conversion and dissipation mechanism in the process of droplet jumping driven by electrowetting, a theoretical reference is provided for the application of this technology in solid-liquid separation and three-dimensional digital microfluidics.

Highlights

  • The interfacial energies of the droplet under electrowetting and after removing the voltage, the X-axis represents the base radius of the droplet

  • Overall energy evolution of a droplet over multiple bounce cycles

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Summary

Introduction

Energy conversion during electrically actuated jumping of droplets Liu Xiao-Juan Li Zhan-Qi Jin Zhi-Gang Huang Zhi Wei Jia-Zheng 热光伏能量转换器件的热力学极限与优化性能预测 Thermodynamic limit and optimal performance prediction of thermophotovoltaic energy conversion devices 物理学报. 用于提高微波无线能量传输系统接收端能量转换效率的肖特基二极管 Ge Schottky diode for improving energy conversion efficiency of the receiver of microwave wireless power transfer 物理学报. 界面羟基对碳纳米管摩擦行为和能量耗散的影响 Influences of hydroxyl groups on friction behavior and energy dissipation of carbon nanotube 物理学报.

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