In this paper, we present a nanostructured ZnO based superhydrophobic high dielectric constant ( K) composite dielectric for EWOD digital microfluidic device for application in mu-TAS. Two fabrication methods of nannosturctured ZnO superhydrophobic surface are studied. Through electrochemical deposition, a nanostructured ZnO film with a dielectric constant of 6.21 and a maximum contact angle of 158.9 degrees is achieved. To prevent electrical leakage, a high dielectric constant barrier is combined with hydrothermal synthesis of ZnO nanorods. The contact angle reaches 164.8 degrees on the composite surface with a contact angle hysteresis of 11.3 degrees. Enhancement of optical signal detected on the superhydrophobic layer is demonstrated. Using such superhydrophobic high K composite material in EWOD digital microfluidics for application in mu-TAS is proposed and has shown its potential feasibility. (C) Koninklijke Brill NV, Leiden, 2011