电驱动引发液滴弹跳过程中的能量转换  

Energy conversion during electrically actuated jumping of droplets

作　　者：刘小娟[1] 李占琪[1] 金志刚[1] 黄智[1] 魏加争[1] 赵存陆 王战涛 Liu Xiao-Juan;Li Zhan-Qi;Jin Zhi-Gang;Huang Zhi;Wei Jia-Zheng;Zhao Cun-Lu;Wang Zhan-Tao(College of Mechanical and Electrical Engineering,Zhongshan Polytechnic,Zhongshan 528400,China;School of Energy and Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]中山职业技术学院机电工程学院,中山528400 [2]西安交通大学能源与动力学院,西安710049

出　　处：《物理学报》2022年第11期238-246,共9页Acta Physica Sinica

基　　金：广东省普通高校重点领域专项(批准号:2020ZDZX084);中山市2021年基础研究重点项目(批准号:2021B2016)资助的课题.

摘　　要：许多工业技术如凝结散热和燃料电池等要求实现固液分离,电润湿是引发液滴从疏水表面脱离的一种有效的方法,而且方便控制.电场激励的液滴弹跳依赖于表面能向动能和其他形式能量的转化,目前尚缺乏对这一过程的深入研究.本研究利用高速摄像机捕捉了在电润湿激励下疏水表面液滴的弹跳运动,根据接触角和液滴形态的变化预估了引发液滴弹跳的电压阈值,并利用自编Matlab程序分析和计算了在液滴脱离表面和反复弹跳过程中各种形式的能量.结果表明,液滴质心的动能和势能在液滴脱离表面飞行期间存在明显的耦合关系,振动动能和表面势能在飞行阶段也存在一定的耦合关系,液滴黏性引起的内部耗散随着液滴振荡变形的幅度增大,并随着时间衰减.由于可以引发液滴振荡变形并制造更多的表面能,在液滴弹跳中交流脉冲比直流电更高效.通过揭示电润湿驱动的液滴弹跳过程中能量的转化和耗散机制,为该技术在固液分离和三维数字微流控中的应用提供了理论参考.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.

关 键 词：电润湿 弹跳 能量 转换 耗散 

分 类 号：O35[理学—流体力学]