In this study, the effect of various parameters on the dispensed droplet size in microchannels based on the electrowetting on dielectric (EWOD) technique is experimentally investigated. A PCB-based microfluidic chip is used as a platform for the experiments. A crescent configuration for the channel electrodes is fabricated that leads to a higher electrowetting force which improves the motion of the droplet. In addition, two electrode designs are proposed which provide a nearly constant overlapping length on the reservoir electrode. The focus of this paper is on the geometry of the reservoir and channel electrode; therefore, the channel dimensions, surface conditions and applied voltage are kept constant. The experiments are performed for various reservoir liquid volumes as well as different electrode shapes of the reservoir and the microchannel. The results show that decreasing the length of the small reservoir electrode reduces the size of the dispensed droplet. It is also observed that using a channel electrode curved in the opposite direction of the droplet motion leads to a smaller dispensed droplet.

Keywords