Abstract
A study was conducted of preparation techniques for superhydrophobic and oleophobic surfaces by forming a roughened surface and preparing a hydrophobic monolayer, which never fills up the roughened surface when the roughned surface is coated by the monolayer. In this study, the techniques employed in preparation of the surfaces consisted of the following two steps.
(1) Forming of a fractal-like structure on the surface of an aluminum substrate by sand-blasting and the electrolytic etching, wherein roughness was obtained at the microlevel by sand-blasting and further roughness was obtained at the nanolevel by the electrolytic etching after the sandblasting.
(2) Modification of the roughened surface of the substrate with a HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane) monolayer, wherein the HDFS monolayer was prepared by means of a chemical adsorption technique, which provides a surface with the lowest surface energy surface on earth.
The largest contact angles obtained with water and oil in this study were ϑw=152° and ϑo=135°, respectively. The optimum conditions of these roughnesses were ca. 150 μm with sand-blasting and tens of nm with electrolytic etching.
