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

Evaluating the anodized tantalum pentoxide (Ta
₂
O
₅
) 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 Ta
₂
O
₅
layer prepared by anodizing a sputtered Ta
₂
O
₅
film. This sputtered-anodized Ta
₂
O
₅
allows the use of positive dc signals, while maintaining the low-voltage actuation for which the anodized Ta
₂
O
₅
was originally introduced. All the EWOD tests were performed with a conductive liquid droplet in an air environment.