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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 50: Wetting, Nano- and Microfluidics I (joint session CPP/DY, organized by CPP)

CPP 50.1: Hauptvortrag

Donnerstag, 10. März 2016, 09:30–10:00, H42

Provoking liquids to dewet and to slide: About concave drops and hungry droplets — •Karin Jacobs — Experimental Physics, Saarland University, D-66041 Saarbrücken

Usually, liquids exhibit a ’no-slip’ boundary condition to a solid substrate, i.e. the atoms or molecules of a liquid that are the closest to the solid substrate are at rest. However, a polystyrene film that moves over hydrophobized (by a self-assembled monolayer of silanes) Si wafers can be provoked to slide, i.e. there is a non-zero interfacial velocity of the fluid in contact with the solid, and friction occurs [1,2]. This implies variations in the energy dissipation mechanisms in these systems and leads to a strikingly different behaviour of fluids in different geometric situations [3-5]: With slip, the dewetting of flat films is faster on solid surfaces (A), Rayleigh-Plateau-type instabilities exhibit an increased dynamics (B) and droplets that were prepared in a non-equilibrium situation can reach equilibrium via a stadium where their topology is concave (C). Yet, why does a liquid slide? Possible explanations including recent findings by scattering methods will be reviewed. Moreover, if more liquids were sliding, would that change things in our everyday life?

[1] O. Bäumchen et al., PRL 113 (2014) 014501; [2] J. D. McGraw et al., Colloid and Interface Science 210 (2014) 13; [3] S. Haefner et al., Nature Comm. 6 (2015) 7409; [4] S. Haefner, O. Bäumchen, K. Jacobs, Soft Matter 11 (2015) 6921; [5] J. McGraw et al., (submitted)