Wettability State Transition and Interfacial Slip Analysis of the Hydrophobic Nanostructure Surface Controlled by an Electric Field

Superhydrophobicity is widely used for reducing drag in pipeline transportation and preventing corrosion of metals. Interfacial slip is the leading factor of hydrophobic surface drag reduction. The presence of a gas–liquid interface is determined by the wetting state of a liquid on the surface. Therefore, investigating the influence of the wetting state on the interfacial slip is essential. In this study, an electric field was used to control the wetting state of a hydrophobic surface. Microchannel and micro-particle image velocimetry technologies were simultaneously used to investigate the effect of different wetting states on interfacial slip characteristics and to explore the mechanism of influence of these wetting states. As the performance changed from the Cassie contact state to the Wenzel contact state, the gas–liquid contact interface gradually moved downward and the interface slip weakened. The Wenzel contact state was achieved by filling the liquid to the bottom of the structure, and the gas–liquid interface and the interface slip disappeared. Consequently, the hydrophobic surface lost the drag reduction effect.