Adjustable Hydrophobicity of Al Substrates by Chemical Surface Functionalization of Nano/Microstructures

Abstract

Superhydrophobic and self-cleaning surfaces may arise due to interplay between nano/microstructures at the solid surface and the chemical properties of the topmost monolayer. In the present work, those relationships were investigated by Al substrate modifications via chemical functionalization with trimethoxypropylsilane dipping, and coating with a thin perfluorinated layer. The effect of the nano/micromorphology on the superhydrophobicity and hysteresis was studied using two main approaches: (i) chemical etching of Al substrates and chemical surface functionalization and (ii) anodic aluminum oxide template (nanoporous) generated on the etched Al substrates and functionalization as in approach i. The physical and chemical properties of the treated substrates were evaluated using water contact angle (WCA) and scanning electron microscopy and by chemical surface-sensitive techniques. The fabricated synthetic surface by approach i was superhydrophobic with a hysteresis of ∼17°. Samples prepared by approach ii showed a WCA of (165 ± 2)° with a very low hysteresis (<3°). A superhydrophobic nanostructure superimposed on a microstructure is the main cause of the self-cleaning properties obtained in the treated Al substrates.