Wetting and Roughness: Part 1

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Wetting and Roughness: Part 1

Authors: David Quere

Annu. Rev. Mater. Res. 2008. 38:71–99

Soft matter keywords

microtextures, superhydrophobicity, wicking, slip

By Alex Epstein

Abstract from the original paper

We discuss in this review how the roughness of a solid impacts its wettability. We see in particular that both the apparent contact angle and the contact angle hysteresis can be dramatically affected by the presence of roughness. Owing to the development of refined methods for setting very well-controlled micro- or nanotextures on a solid, these effects are being exploited to induce novel wetting properties, such as spontaneous filmification, superhydrophobicity, superoleophobicity, and interfacial slip, that could not be achieved without roughness.

In Part 1, we look at the sections Microtextured Solids and Hemiwicking 

Soft matters

Brief Intro

One of the authors of our course text, David Quere, authored this lovely review paper, which focuses on how the roughness of a solid affects its wettability. Controlling wettabilty of a solid surface is of great interest in many engineering contexts. The extremes, complete wetting and complete drying, are particularly desirable. Windshields should have a uniform film to maintain the glass transparency, and to remove dust particles as in flows under gravity or air flow. Surfaces that must have no liquid contamination should force drops to be spherical and virtually without contact, so that they roll off.

In the classical case of flat and chemically homogeneous solids explored by Young and Laplace, the relationship between the three interfacial surface tensions (equivalent to surface energies) determines the wetting condition. As Marangoni explained, a film extends from a liquid reservoir on a wetting solid, replacing <math>\gamma_{SA}</math> b by <math>(\gamma_{SL} + \gamma_{LA}</math> if the spreading coefficient <math>S = \gamma_{SA} - \gamma_{SL} - \gamma_{LA}</math>.

Fig. 1