Biomimetic water-repelling hierarchical surfaces

Abstract

Nature is the great source of inspiration for creating unique structures with special functions. The termite wing, one of the representative examples of water-repelling surfaces, consists of an array of long hairs and nanoarchitecture with different dimension scale. Herein, we introduced a method of preparing hierarchical structures and water-repellency of the surfaces with different drop impact scenarios. Hierarchical structures were prepared with mixtures of UV-curable polyurethane acrylate (PUA) and silica moiety using the replica molding technique, followed by the selective oxygen plasma etching of PUA. In order to achieve the enhanced hydrophobicity, fluorinated moieties were attached to the etched surfaces to lower the surface energy. As a result, these hierarchical surfaces showed many different drop impact scenarios by varying impact speed, drop size, and the geometry of the surfaces. Finally, TiO2 nanoparticles were introduced to fabricate 3-tier hierarchical structures in order to enhance superhydrophobicity by enlarging the surface area, resulting in extremely high water-repellency and high transparency for future applications.