Mechanically Durable Superhydrophobic Surfaces

Abstract

Development of durable non-wetting surfaces is hindered by the fragility of the microscopic roughness features that are necessary for superhydrophobicity. Mechanical wear on superhydrophobic surfaces usually shows as increased sticking of water, leading to loss of non-wettability. Increased wear resistance has been demonstrated by exploiting hierarchical roughness where nanoscale roughness is protected to some degree by large scale features, and avoiding the use of hydrophilic bulk materials is shown to help prevent the formation of hydrophilic defects as a result of wear. Additionally, self-healing hydrophobic layers and roughness patterns have been suggested and demonstrated. Nevertheless, mechanical contact not only causes damage to roughness patterns but also surface contamination, which shortens the lifetime of superhydrophobic surfaces in spite of the self-cleaning effect. The use of photocatalytic effect and reduced electric resistance have been suggested to prevent the accumulation of surface contaminants. Resistance to organic contaminants is more challenging, however, oleophobic surface patterns which are non-wetting to organic liquids have been demonstrated. While the fragility of superhydrophobic surfaces currently limits their applicability, development of mechanically durable surfaces will enable a wide range of new applications in the future.

The icephobic performance of alkyl-grafted aluminum surfaces

“…Relatively poor or reduced performance was reported for several types of SHSs tested under repeated icing/deicing conditions [15,16,22,29,31], which was attributed to their poor abrasive resistance (also reported by others in a concise review [32]). In parallel, SHSs were reported to lose their anti-icing performance in a humid atmosphere, when icing follows (or occurs simultaneously with) water condensation or frost formation in their rough structures [2,13,16,22,33].…”

Free-decay and resonant methods for investigating the fundamental limit of superhydrophobicity

“…Moreover, surface defects and surface inhomogeneity are challenging to probe by using any of the conventional methods. Thus, new approaches are needed for studying directly the energy dissipation in dynamic moving droplets under well-defined lateral and normal forces, in order to understand energy dissipation, defects and wear on the intrinsically fragile superhydrophobic surfaces 32 .…”

Recent developments in polymeric superoleophobic surfaces

“…Compared with many years of development on durability of superhydrophobic surfaces, 124 the research on superoleophobic surfaces has just begun. Wang et al reported a superoleophobic rough alumina surface with selfhealing property, which showed good durability to external mechanical damage.…”