Transient dynamics of the moving meniscus

Abstract

Microfluidic schemes exploiting electromechanical forces such as electrowetting-on-dielectric (EWOD) and dielectrophoresis (DEP) combine high speed with geometric simplicity and voltage-based control. While the hydrostatic behavior of these devices has been studied extensively, the dynamics have received far less attention. Particularly important is the strongly-coupled interfacial behavior of the moving contact line. This behavior encompasses the contact angle and the profile of the moving interface, interfacial vibrations due to AC voltage, and a frictional, dynamic “line force ” that impedes forward displacement of the liquid. In the past, we used Pellat’s experimental geometry to observe time-dependent height-of-rise as a function of voltage, electrode spacing, and frequency [1]. Se Fig. 1. We are now investigating the transient behavior of the rising liquid column, using a high-speed camera to record meniscus shape, contact angle, and contact lin