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A new model for contact angle hysteresis

TitleA new model for contact angle hysteresis
Publication TypePreprint
AuthorsDeSimone, A, Gruenewald, N, Otto, F
Series TitleNetw. Heterog. Media 2 (2007) 211-225
Document NumberSISSA;37/2006/M

We present a model which explains several experimental observations relating contact angle hysteresis with surface roughness. The model is based on the balance between released energy and dissipation, and it describes the stick-slip behavior of drops on a rough surface using ideas similar to those employed in dry friction, elasto-plasticity and fracture mechanics. The main results of our analysis are formulas giving the interval of stable contact angles as a function of the surface roughness. These formulas show that the difference between advancing and receding angles is much larger for a drop in complete contact with the substrate (Wenzel drop) than for one whose cavities are filled with air (Cassie-Baxter drop). This fact is used as the key tool to interpret the experimental evidence.

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