Superhydrophobic Surface Based on a Coral-Like Hierarchical Structure of ZnO

Abstract

BackgroundFabrication of superhydrophobic surfaces has attracted much interest in the past decade. The fabrication methods that have been studied are chemical vapour deposition, the sol-gel method, etching technique, electrochemical deposition, the layer-by-layer deposition, and so on. Simple and inexpensive methods for manufacturing environmentally stable superhydrophobic surfaces have also been proposed lately. However, work referring to the influence of special structures on the wettability, such as hierarchical ZnO nanostructures, is rare.MethodologyThis study presents a simple and reproducible method to fabricate a superhydrophobic surface with micro-scale roughness based on zinc oxide (ZnO) hierarchical structure, which is grown by the hydrothermal method with an alkaline aqueous solution. Coral-like structures of ZnO were fabricated on a glass substrate with a micro-scale roughness, while the antennas of the coral formed the nano-scale roughness. The fresh ZnO films exhibited excellent superhydrophilicity (the apparent contact angle for water droplet was about 0°), while the ability to be wet could be changed to superhydrophobicity after spin-coating Teflon (the apparent contact angle greater than 168°). The procedure reported here can be applied to substrates consisting of other materials and having various shapes.ResultsThe new process is convenient and environmentally friendly compared to conventional methods. Furthermore, the hierarchical structure generates the extraordinary solid/gas/liquid three-phase contact interface, which is the essential characteristic for a superhydrophobic surface.

Wettability properties of PTFE/ZnO nanorods thin film exhibiting UV-resilient superhydrophobicity

“…Wu et al [18] have also used hydrothermal method to grow ZnO followed by spin-coating of Teflon on it to produce a coral-like hierarchical structure of ZnO with superhydrophobic property. Among polymers, polytetrafluoroethylene (PTFE, Teflon) has been widely used for coatings specially for surface water repellency [19].…”

Nanotextured Shrink Wrap Superhydrophobic Surfaces by Argon Plasma Etching

“…However, these approaches typically require additional post-processing using chemicals to decrease the surface energy [11,24,25]. Chemical modifications can cause health and environmental concerns due to the possibility of chemical leaching [26].…”

Preparation of hierarchical porous Zn-salt particles and their superhydrophobic performance

“…A few studies have explored the superhydrophobic surfaces synthesized from the growth of ZnO crystals in liquid phase [37,38]. However, these crystals usually form columnar nanorods…”