Wang K-L, Jones T B
Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627, USA.
Langmuir. 2005 Apr 26;21(9):4211-7. doi: 10.1021/la0468702.
When voltage is suddenly applied to vertical, parallel dielectric-coated electrodes dipped into a liquid with finite conductivity, the liquid responds by rising up to reach a new hydrostatic equilibrium height. On the microfluidic scale, the dominating mechanism impeding this electromechanically induced actuation appears to be a dynamic friction force that is directly proportional to the velocity of the contact line moving along the solid surface. This mechanism has its origin in the molecular dynamics of the liquid coming into contact with the solid surface. A simple reduced-order model for the rising column of liquid is used to quantify the magnitude of this frictional effect by providing estimates for the contact line friction coefficient. Above some critical threshold of voltage, the electromechanical force is clamped, presumably by the same mechanism responsible for contact angle saturation and previously reported static height-of-rise limits. The important distinction for the dynamic case is that the onset of the saturation effect is delayed in time until the column has risen more than about halfway to its static equilibrium height.
当突然对浸入具有有限电导率液体中的垂直平行介电涂层电极施加电压时，液体会通过上升达到新的静水力学平衡高度来做出响应。在微流体尺度上，阻碍这种机电诱导驱动的主要机制似乎是一种动态摩擦力，它与沿固体表面移动的接触线速度成正比。这种机制源于与固体表面接触的液体的分子动力学。通过提供接触线摩擦系数的估计值，使用一个简单的降阶模型来量化上升液柱的这种摩擦效应的大小。在高于某个临界电压阈值时，机电力被钳制，推测是由导致接触角饱和和先前报道的静态上升高度限制的相同机制所致。动态情况的重要区别在于，饱和效应的开始在时间上延迟，直到液柱上升到超过其静态平衡高度的一半左右。
