Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 57: Solid / liquid interfaces II

O 57.5: Talk

Wednesday, March 28, 2012, 17:45–18:00, A 060

Analyzing the hydrodynamic boundary condition at solid-liquid interfaces with fluorescence correlation spectroscopy — Stoyan Yordanov, David Schäffel, Roman Schmitz, Burkhard Dünweg, Kaloian Koynov, and •Hans-Jürgen Butt — Max-Planck-Institut für Polymerforschung, Mainz, Deutschland

An important step towards an understanding of hydrodynamics is determining the correct boundary conditions. A new method for direct studies of flows in the close proximity of a solid surface has been developed. It is based on total internal reflection fluorescence cross-cor-relation spectroscopy (TIR-FCCS).

The effect of TIR is used to create an evanescent optical field that excites fluorescent tracer particles flowing with the liquid. A high numerical aperture microscope objective is employed to monitor simultaneously the fluorescent light from two small and laterally shifted (in flow direction) observation volumes. A cross-correlation of the fluorescent signals from these volumes yields the tracers and hence the flow velocity. By tuning the TIR conditions and therefore the evanesced wave penetration depth we can determine flow velocity profiles in the range 0-300 nm from the interface.