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Simple model to describe adaptive wetting

Hans-Jürgen Butt Physics at Interfaces, Max Planck Institute For Polymer Research, Mainz

The dynamics of a liquid wetting a solid surface is a complex process because different length scales and several times scales are involved. Even on inert, rigid, smooth and homogeneous surfaces a quantitative description of wetting dynamics is still a challenge. This challenge becomes even bigger for adaptive or responsive surfaces. Here, we are concerned with surfaces, which spontaneously change in the presence of the liquid or its vapor. For simplicity we use the term “adaptivity” in that narrow sense. A simple model is introduced to understand and model wetting dynamics, focusing on temporal and spatial changes of the interfacial energies. The aim of the model is to provide a quantitative description of adaptive wetting and to link changes in contact angles to a microscopic adaptation processes. The model provides a framework for a discussion of adaptive wetting and focus the discussion to relevant questions. Adaptation can explain the sometimes observed changes in contact angle even at low speeds of the contact line. Adaptation can also explain contact angle hysteresis even on smooth, homogeneous surfaces.