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.

Permanent superhydrophobic polypropylene nanocomposite coatings by a simple one-step dipping process

“…Surfaces with high Ti-OH concentrations will increase the work of adhesion and their CAHs. Our previous chemical studies on superhydrophobic surfaces also showed that the chemical heterogeneity on the surface strongly influences the final dynamic properties of a superhydrophobic surface [22,[45][46][47].…”

“…By dicing [21] or laser photolithography [8] several hydrophobic micro structures were prepared; experimental results were compared with those of Wenzel-Cassie models. Superhydrophobic alumina films have been successfully developed on industrial aluminum foils by a simple anodization method following by chemical surface modification [22,23].…”

Adjustable, (super)hydrophobicity by e-beam deposition of nanostructured PTFE on textured silicon surfaces

“…For over a decade, several methods to obtain superhydrophobic surfaces have been developed due to great industrial interest in reducing flow resistance and fluidic drag [1], in repairable superomniphobic surfaces [2], in applications such as optical antireflection [3], corrosion protection [4], liquid transportation [5], biochemical separation [6], antibiofouling paints for boats, production of food packaging, inhibition of ice or snow adhesion [7,8], and self-cleaning surface properties [9]. Although easydewetting surfaces can be obtained in flat/smooth surfaces even with low contact angle [10], superhydrophobic surfaces with self-cleaning properties are usually characterized by exhibiting a very high Contact Angle (CA) and low Contact Angular Hysteresis [11].…”

“…In order to increase surface roughness, there are two possibilities: the first one is thorough its generation on the substrate, such as by plasma etching [13], chemical etching [14] or embossing [15]; the second is thorough incorporation of a coating on the substrate, such as by electrospinning [16][17][18], chemical vapor deposition [19][20][21][22][23], lithography [24,25], dip coating [26,27], anodic aluminum oxide [9,28] [29,30] or physical vapor deposition (PVD) [15,31]. Hierarchical structures, i.e., with micro-and nanostructure, have been reported for stability of the superhydrophobic condition [24].…”

“…Particularly regarding chemical composition, wettability, and morphology, RF-sputtered PTFE coatings were grown under several bias voltages and gas compositions on silicon wafers [42,43]. Thermally evaporated PTFE films have also been reported on several substrates, such as Aluminum [9], glass [44] intermetallic oxide alloys [45], micro-and nano-crystalline diamond-like carbon [46,47] to promote low surface energy and surface nano-roughness. High-energy electron irradiation was used for the chemical modification of bulk PTFE [48][49][50][51][52].…”