One-step to synthesize multilevel structured ZnO films with exceptional wettability

A facile one-step synthesis approach was developed to prepare ZnO films with multilevel structures composed of microclusters and nanohairs. The hierarchically structured ZnO films demonstrate peculiar wettability-superhydrophobicity but with high normal adhesion. The very high aspect-ratio of ZnO nanohairs minimizes the area of the (002) high potential surface which is the preferential growth direction. Microclusters of ZnO ensure the sufficient short-distance interactions for the normal adhesion, while the overall ZnO platforms with unique geometrical configuration and chemical composition provide the bulk scale conformity necessary for superhydrophobicity and high adhesion for rough or contoured surfaces. The superhydrophobicity of the ZnO nanohair films can be explained with the Cassie impregnating model or partial wetting model. Thanks to its purity as an inorganic material, the superhydrophobic ZnO films exhibit outstanding durability.