Fabrication of robust superhydrophobic surfaces by one-step spray coating: Evaporation driven self-assembly of wax and nanoparticles into hierarchical structures

Mechanically durable superhydrophobic coatings have enormous application potential in almost all aspects of our daily lives. In this study, we present a practical strategy for one-step fabrication of robust superhydrophobic coatings based on evaporation driven self-assembly of hydrophobic nanoparticles and wax into hierarchical structures. Depending on the solvent and coating distance, spray-coating a dispersion composed of alkyl-silane functionalized nanoparticles and wax results in extremely water repellent surfaces with a water contact angle of 175° and a sliding angle of 3°. The formation of hierarchically structured surfaces upon evaporation of the solvent enables fabrication of fluorine-free, highly water repellent surfaces and provides high level of structural protection against mechanical abrasion. The coating retains its superhydrophobicity even after 1000 cycles of water spray impact, 45 min of water jet impact, and 180 cm of linear abrasion. The low-cost, scalable, one-step, and fluorine-free fabrication of superhydrophobic coatings that can be applied onto virtually any type of material surface with a satisfactory mechanical robustness based on eco-friendly and industrially available materials presents promising avenues for practical applications.