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Adaptive Wetting—Adaptation in Wetting

Butt, Hans-Jürgen, Berger, Rüdiger, Steffen, Werner, Vollmer, Doris, Weber, Stefan A. L.
Langmuir 2018 v.34 no.38 pp. 11292-11304
adsorption, contact angle, energy, equations, hysteresis, kinetics, liquids, models, polymers, surfactants
Many surfaces reversibly change their structure and interfacial energy upon being in contact with a liquid. Such surfaces adapt to a specific liquid. We propose the first order kinetic model to describe dynamic contact angles of such adaptive surfaces. The model is general and does not refer to a particular adaptation process. The aim of the proposed model is to provide a quantitative description of adaptive wetting and to link changes in contact angles to microscopic adaptation processes. By introducing exponentially relaxing interfacial energies and applying Young’s equation locally, we predict a change of advancing and receding contact angles depending on the velocity of the contact line. Even for perfectly homogeneous and smooth surfaces, a dynamic contact angle hysteresis is obtained. As possible adaptations, we discuss changes and reconstruction of polymer surfaces or monolayers, diffusion and swelling, adsorption of surfactants, replacement of contaminants, reorientation of liquid molecules, or formation of an electric double layer.