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Issue 40, 2016
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Deviation of sliding drops at a chemical step

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The motion of partially wetting liquid drops in contact with a solid surface is strongly affected by contact angle hysteresis and interfacial pinning. However, the majority of models proposed for drops sliding over chemical surface patterns consistently neglect the difference between advancing and receding contact angles. In this article, we present a joint experimental and numerical study of the interaction of gravity-driven drops with a chemical step formed at the junction between a hydrophilic and a hydrophobic region. It demonstrates the strong impact of a contact angle hysteresis contrast on the motion of drops at a linear chemical step. Surprisingly, the smallest driving force required to drag the drop across the step onto the lower hydrophobic surface is not observed at a right angle of incidence. Our model reveals that the non-monotonous response of this passive drop ‘filter’ is solely due to the higher advancing contact angle on the lower surface, and creates an instance where drop motion is affected by dissipation at the contact line rather than by surface energy.

Graphical abstract: Deviation of sliding drops at a chemical step

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The article was received on 09 May 2016, accepted on 28 Jul 2016 and first published on 28 Jul 2016

Article type: Paper
DOI: 10.1039/C6SM01077F
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Citation: Soft Matter, 2016,12, 8268-8273
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    Deviation of sliding drops at a chemical step

    C. Semprebon, S. Varagnolo, D. Filippi, L. Perlini, M. Pierno, M. Brinkmann and G. Mistura, Soft Matter, 2016, 12, 8268
    DOI: 10.1039/C6SM01077F

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