Tutorial: Can Nanostructuring Improve the Properties of Hydrophobic Surfaces?

This synopsis discusses the effects of surface structures of nanometer dimensions on the hydrophobicity of a material. They are investigated by atomistic molecular dynamics simulations of water and salt solutions near appropriately structured model surfaces designed to represent hydrocarbon and fluorocarbon materials. It is found that surface structuring does increase the hydrophobicity of these already inherently hydrophobic materials, and that, among the structures investigated, circular holes and protrusions of about 2.5 nm diameter and 0.5 nm depth or height, respectively, are most effective. The mechanism of the hydrophobicity increase is molecular and different from the macroscopic lotus effect: Water assumes a much reduced, but still liquid‐like density around the surface structures. It does not avoid them altogether. The hydrophobicity increase due to surface nanostructuring is material‐independent and is also present at higher temperatures and for aqueous alkali halide solutions.