Sen Prosenjit, Kim Chang-Jin C J
Mechanical and Aerospace Engineering Department, University of California, Los Angeles (UCLA), California 90095, USA.
Langmuir. 2009 Apr 21;25(8):4302-5. doi: 10.1021/la900077u.
We report the contact line dynamics of sessile water droplets, 1.1-1.6 mm in radius, spread by electrowetting in air. Coplanar electrodes patterned on the substrate allow a true sessile condition with no wire into the droplet. The frequency response of the droplets is studied using 25 VAC ranging from 10 to 205 Hz. The effect of contact angle hysteresis is seen in form of stick-slip motion. A model developed provides a good match to the experimental result. Step response is studied with voltages in the range of 20-80 VDC. Two regimes of motion are observed. In the first regime, local flows cause the contact line speed to increase and reach a maximum while the contact angle is still changing. Global flows in the second regime cause the contact line to move with a reduced speed and attain the spherical shape pertaining to the new equilibrium contact angle. A model is used to describe the motion.
我们报告了半径为1.1 - 1.6毫米的静止水滴在空气中通过电润湿展开时的接触线动力学。在基板上图案化的共面电极实现了真正的静止状态，没有导线插入液滴。使用25伏交流电，频率范围为10至205赫兹，研究了液滴的频率响应。接触角滞后的影响以粘滑运动的形式出现。所开发的模型与实验结果匹配良好。使用20 - 80伏直流电压研究了阶跃响应。观察到两种运动状态。在第一种状态下，局部流动使接触线速度增加并达到最大值，而接触角仍在变化。第二种状态下的整体流动使接触线以降低的速度移动，并达到与新的平衡接触角相关的球形形状。使用一个模型来描述这种运动。
