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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Wetting, Superamphiophobicity, Micro- and Nanofluidics I

CPP 18.8: Vortrag

Dienstag, 1. April 2014, 11:30–11:45, ZEU 222

Slip effects in dewetting polymer microdroplets — •Joshua D. McGraw¹, Thomas Salez², Simon Maurer¹, Tak Shing Chan^1,3, Michael Benzaquen², Jonas Heppe¹, Martin Brinkmann^1,3, Élie Raphaël², and Karin Jacobs¹ — ¹Saarland University, Experimental Physics, D-66041 Saarbrücken — ²Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI, Paris, France — ³Max Planck Institute for Dynamics & Self-Organization, 37077 Göttingen

Spherical caps on a substrate with less than equilibrium contact angles contract as a result of capillary forces. Applying the classical no-slip condition at the liquid-substrate interface results in diverging stress at the contact line. This divergence can be alleviated, however, by allowing finite flow velocity at the substrate, corresponding to the slip boundary condition. Experiments have been conducted in which glassy polystyrene microdroplets are placed upon, as substrates, different self-assembled monolayers (SAMs). The spherical caps are prepared such that initial contact angles are much less than the equilibrium contact angle. Above the glass transition temperature, a capillary induced flow is observed; the droplet radii shrink while their heights grow. Furthermore, the intermediate height profiles are highly non-spherical. Different SAMs give rise to differing slip lengths, resulting in dramatic changes to the temporal and morphological path these tiny droplets take toward their equilibrium spherical cap shapes.