Wettability control of ZnO nanoparticles for universal applications.

Herein, a facile approach for the fabrication of a superhydrophobic nanocoating through a simple spin-coating and chemical modification is demonstrated. The resulting coated surface displayed a static water contact angle of 158° and contact angle hysteresis of 1°, showing excellent superhydrophobicity. The surface wettability could be modulated by the number of ZnO nanoparticle coating cycles, which in turn affected surface roughness. Because of its surface-independent characteristics, this method could be applicable to a wide range of substrates including metals, semiconductors, papers, cotton fabrics, and even flexible polymer substrates. This superhydrophobic surface showed high stability in thermal and dynamic conditions, which are essential elements for practical applications. Furthermore, the reversible switching of wetting behaviors from the superhydrophilic state to the superhydrophobic state was demonstrated using repeated chemical modification/heat treatment cycles of the coating films.