Electrowetting on ZnO nanowires

In this paper, we study the electrowetting character on ZnO nanowires. We grow the ZnO nanowires on indium tin oxide (ITO) by a hydrothermal method, and the ZnO nanowires surface is further hydrophobized by spin-coating Teflon. Such a prepared surface shows superhydrophobic properties with an initial contact angle 165A degrees. When the applied external voltage between the ITO and the sessile droplet is less than 50 V, the contact angle continuously changed from 165A degrees to 120A degrees, and exhibits instant reversibility. For a slightly higher voltage, a mutation of the contact angle changing to 100A degrees was observed and the contact angle was not reversible after removing the applied voltage, which indicates a transition from non-wetting state to wetting state. Further increasing of the applied voltage, the apparent contact angle decreased to an invariable value 70A degrees, and electrical breakdown emerged synchronously.