Droplet Transportation on Vertical Parallel Electrodes Using Electrowetting and Interfacial Oscillation

Abstract

In this study, we demonstrate the transportation of small liquid droplet on vertical parallel electrodes using electrowetting phenomena and the interfacial oscillation. The transportation of liquid droplets, which can be applied to droplet-based biochemical devices, is performed by applying AC voltage that ranges from 0 to 100 V_pp and from 20 to 100 Hz. The flow characteristics are observed by a high speed camera, and the effects of interfacial oscillation and the dynamic contact angle on the droplet motion are investigated in detail. The experimental results show that the vertical velocity of the droplet can be controlled by changing the amplitude and the frequency of the applied AC voltage. Furthermore, the dynamics of the droplet are estimated theoretically considering the interfacial tension due to the dynamic contact angle and the gravitational force. The predicted force and the displacement of the droplet reasonably agree with the experimental values obtained from the high speed observation of the droplet motion.