Sputtered–Anodized $\hbox {Ta}_{2}\hbox {O}_{5}$ as the Dielectric Layer for Electrowetting-on-Dielectric

Evaluating the anodized tantalum pentoxide (Ta₂O₅) that has been recently reported as a dielectric for low-voltage electrowetting-on-dielectric (EWOD) devices, we find a severe deterioration in performance if the working liquid is actuated with positive dc voltage. In an effort to reduce the limitation of this otherwise attractive dielectric material for EWOD, proposed herein is a Ta₂O₅ layer prepared by anodizing a sputtered Ta₂O₅ film. This sputtered-anodized Ta₂O₅ allows the use of positive dc signals, while maintaining the low-voltage actuation for which the anodized Ta₂O₅ was originally introduced. All the EWOD tests were performed with a conductive liquid droplet in an air environment.