This paper presents test structures designed for studying the relationship between the operation voltage and the configuration of electrode area for coplanar EWOD (ElectroWetting On Dielectrics) devices. Robust anodic Ta 2O5 dielectric and thin aFP (amorphous Fluoropolymer) have been used to fabricate the structures. Test structures have been used to characterise the significant contact angle change on asymmetric configurations, 114° to 81° on CYTOP (amorphous fluoropolymer from Asahi Glass Co. Ltd.) with an applied voltage of less than 20V. This demonstrates that by modifying the design, the operating voltage can be reduced by a factor of two, compared to the existing symmetric coplanar EWOD structures. Droplet manipulation on a coplanar EWOD system with this new design has been successfully demonstrated, with a driving voltage of 15V.