Robust superhydrophobic and icephobic surface based on Teflon AF coated multiscale hierarchical ZnO/Cu2O nanostructures

Abstract

We demonstrate hetero-nanostructured rough surface with solution based hydrophobic coating for robust superhydrophobic (SH) properties. The copper foil was anodically etched to generate Cu2O micro-needles and then ZnO nanorods were grown on Cu2O to create ZnO/Cu2O micro-nano hierarchical rough surface. A thin layer of Teflon AF was applied as a low surface energy coating on the top of the hierarchical surface. These surfaces were characterized for their structural phases using the X-ray diffraction technique and multiscale hierarchical surface morphology was confirmed using FESEM and AFM techniques. Wetting properties like static and dynamic water contact angle (CA) were analyzed using the advancing receding contact angle (ARCA) technique. This surface shows superhydrophobic properties with static CA of 157° and a roll-off angle of 3°. The durability of the SH surfaces was examined by water droplet impact for a range of velocities. The droplet rebounding is consistently seen up to Weber number, We ∼ 220. When the SH surface was cooled to −10 °C, dropwise condensation takes place. In this case, self-propelled jumping of droplets via multiple coalescences of microdroplets was observed. In the freezing rain condition, this surface exhibits poor adhesion to ice formation demonstrating an icephobic property. The surface retains SH properties even to the UVC exposure of about 12 J/cm2. The fabrication of the SH surface involves solution-based processes which are scalable to mass production for applications ranging from enhanced heat conduction to water-repellent coatings.