Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 27: Micro and Nano Fluidics II: Slipping + soft objects in flow

CPP 27.2: Vortrag

Donnerstag, 28. Februar 2008, 14:15–14:30, C 264

Flow of thin polymer films on mesoporous silicon surfaces — •Matthias Lessel, Oliver Bäumchen, and Karin Jacobs — Saarland University, Experimental Physics, D-66123 Saarbrücken, Germany

The nature of boundary conditions of fluids at the interface of solid surfaces has become more and more important in recent years due to applications in lab-on-a-chip devices. Reducing the scale of fluidic systems leads to a stronger influence of this interface, which can be described by a parameter called slip length. It can be interpreted as the length below the solid/liquid interfaces where the velocity profile of the liquid extrapolates to zero. Our system consists of thin polystyrene films on top of hydrophobized Si wafers, which are heated above the glass transition temperature to induce dewetting as a driving force for Newtonian flow. The slip length can be extracted by analyzing the growth of a dewetting hole using optical microscopy or, with the help of a Stokes model for thin liquid films, from rim profiles of holes imaged by AFM. In recent experiments we study the influence of structured surfaces on the dewetting dynamics. For this we are using hydrophobized mesoporous Si substrates instead of a smooth Si wafer bearing in mind that the pore diameter and porosity of this material is alterable by parameters of the fabrication process. Moreover they can be probed by spectroscopic ellipsometry using a fit based on a Bruggeman model.