Droplet transportation on a wettability gradient surface generated by electrowetting-on-dielectric

This paper presents a novel microdevice for droplet transportation using a wettability gradient surface that is generated by EWOD (Electrowetting-on- dielectric). Velocity of a droplet on this device can be controlled by changing the frequency of a square-wave voltage that is applied between two interdigitated and wedge-shaped electrodes. When a square wave voltage of 50 V and 10 Hz was applied, the transportation velocity of a 5 μ,l deionized (DI) water droplet was 3.9 mm/s. Also, we succeeded in transporting not only DI water but also organic solution (dimethyl sulphoxide, DMSO) and electrolyte solution (KCl and phosphate bufferd saline, PBS), and investigated the relationship between their transportation velocities and voltage frequencies. © 2010 The Institute of Electrical Engineers of Japan.