Natural and biomimetic artificial surfaces for superhydrophobicity, self-cleaning, low adhesion, and drag reduction

This paper provides a review of superhydrophobicity and related phenomena (superoleophobicity, omniphobicity, self-cleaning) induced by surface micro- and nanostructuring. The classical approaches to superhydrophobicity using the Young, Wenzel, and Cassie–Baxter models for the contact angle (CA) are presented. After that, the issues that are beyond the Wenzel and Cassie–Baxter theories are discussed, such as multiscale effects, 1D vs. 2D interactions, the effects of contact line, size of roughness details, curvature, and CA hysteresis dependence on roughness. New potential applications of superhydrophobicity are reviewed, such as new ways of energy transition, antifouling, and environment-friendly manufacturing.

Superhydrophobic surfaces and emerging applications: Non-adhesion, energy, green engineering

The stability of a composite interface of roughness-induced superhydrophobic surfaces is studied. To have high contact angle and low contact angle hysteresis, superhydrophobic surfaces should be able to form a composite interface with air pockets in the valleys between asperities (pillars). However, the composite interface may be unstable and can be irreversibly transformed into a homogeneous interface. We formulate a stability criterion and analyze the stability of the composite interface for several typical roughness profiles. To resist destabilizing mechanisms, multiscale (hierarchical) roughness is required. Such multiscale roughness is found in natural and artificial superhydrophobic surfaces.

Multiscale roughness and stability of superhydrophobic biomimetic interfaces.

Review of non-reactive and reactive wetting of liquids on surfaces.

Contact angle measurement on rough surfaces.

The relation between Young’s equilibrium contact angle and the hysteresis on rough paraffin wax surfaces

Measurements of solid-water contact angles in the presence of different vapours

A large number of publications deals with the surface tension of solids derived from wetting experiments [1,2] In some cases, several hypotheses have been proposed to find a relationship between blood compatibility of a surface and its wetting behaviour, its hydrophobic-hydrophilic relation or its surface tension [3,4,5,6] It is important to point out that wetting experiments are correlated with the surface tension of a solid only in those systems where the interfaces are not altered by adsorption This paper describes contact angle measurements according to common procedures with drops, bubbles and plates It presents experimental results from adsorption tests and conclusions for surface research in the future

D. Paul

Papers

The relation between Young’s equilibrium contact angle and the hysteresis on rough paraffin wax surfaces

Measurements of solid-water contact angles in the presence of different vapours

Advancing and Receding Water Contact Angle Measurements with Drops, Bubbles and Plates