Super hydrophobicity of sputtered PTFE films on nanotextured aluminum surface

Abstract

In this research, the superhydrophobic surface was prepared by using the polytetrafluoroethylene (PTFE) thin films which deposited on aluminum (Al) nanotextures. The Al nanotextures have been prepared under different alkaline-treatment concentrations, and deposited with the PTFE thin films by the RF magnetron sputtering technique. During the alkaline treatments, the Al surface was immersed in the potassium hydroxide (KOH) solution with the concentrations of 1 mM to 0.10 mM. Then, the samples of PTFE films were deposited on Al nanotextures were characterized; the crystal structures, chemical compositions, physical morphologies, and surface roughness by photoelectron spectroscopy (PES), field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), respectively. The results show that, after the KOH treatment, the nano flask-like structures were observed on the Al surface. The surface roughness of the prepared samples was also increased with the highly concentrated KOH treatments. In addition, the wettability of the prepared samples was contributed from the presence of the functional groups and surface morphologies, as observed by the X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) analyses. Finally, the results clearly demonstrated that the super-hydrophobic surface could be developed by the PTFE films deposited on the Al nanotextures according to the combination of the small surface-energy material and the surface nanostructures. The influence of the surface nanotextures on the super-hydrophobicity was investigated and discussed, based on the Wenzel and Cassie-Baxter models of the water contact angles on the solid surface.