Super Water- and Oil-Repellent Surfaces Resulting from Fractal Structure

Superoleophobic surfaces: design criteria and recent studies

“…The resulting surface displayed a static contact angle θ * = 150° with rapeseed oil (see Figure 6a). Furthermore, oil droplets rolled around even if the substrate was only slightly tilted 52 indicating low contact angle hysteresis. In more recent work, Fujii et al 53 developed a dual-scale pillared structure of aluminum-niobium alloy by combining oblique angle magnetron sputtering and anodic oxidation.…”

Formation mechanism of super water-repellent fractal surfaces of alkylketene dimer

“…In the former trial, fluorinated compounds with low surface energy were usually used, while several nano-or micro-textured or fractal structures on the surfaces were formed in the later case. Various approaches to prepare super water-repellent surfaces have been reported including melt-solidification of a wax, [11][12][13][14] silica and oxidized alumina films through the sol-gel method, [15][16][17] plasma-based etching or deposition, 18,19 gel-like roughened polypropylene, 20 anodically oxidized aluminum, 21,22 etched copper and electrodeposited copper, 23 electrochemical polymerization, 24 layer-by-layer assembly together with electrodeposition, 25 solution-immersion, 26 polymer/nanoparticle composite films, 27,28 films of aligned carbon nanotubes, polymer nanofibers and inorganic nanorods. [29][30][31][32][33][34][35][36] Effects of geometric length scales, surface roughness and surface energy on the wettability of super water-repellent surfaces were extensively discussed from physical and chemical points of view.…”

“…[37][38][39][40][41][42][43][44][45] It has been well known that fractal structures can effectively magnify the real surface area compared with the projected one, and then enhance the wettability of a solid surface. [11][12][13]21,22,46 Alkylketene dimer (AKD), a kind of wax, was found to form fractal structures spontaneously with a dimension of 2.29 and to give super water-repellent surfaces with the water contact angle as large as 174 o . 11,12 Super water-and oil-repellent surfaces 21,22 with fractal dimension of 2.19 and fractal super water-repellent poly(alkylpyrrole) film 24 with a dimension of 2.23 were also successfully made.…”

Control of morphology and surface wettability of anodic niobium oxide microcones formed in hot phosphate–glycerol electrolytes

“…To make the oxide surface hydrophobic, the anodized specimens were coated with FAP, which was selected for two main reasons. One is that CF 3 -terminal group is the most effective in reducing the surface energy [6] and another is that the fluoroalkyl phosphate is known to bring about higher CAs for water and oil rather than the often used fluoroalkylsilane coupling agents [35]. The FAP-coated anodic niobium oxide films were superhydrophobic, and the static CA for water could not be measured, because of the ready rolling of the water droplet from the surface.…”