Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Confined Fluids

CPP 17.6: Vortrag

Dienstag, 24. März 2009, 11:00–11:15, ZEU 160

Critical Casimir Forces in the presence of varying surface fields — •Ursula Nellen, Laurent Helden, and Clemens Bechinger — 2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart

In 1978 Fisher and de Gennes predicted that the confinement of critical fluctuations in a binary liquid leads to so-called Critical Casimir Forces. Direct experimental measurements of such forces has been only obtained recently. The amplitude of the Critical Casimir Force has been demonstrated to scale with the reduced temperature whereas a variation of the surface field from symmetric to antisymmetric boundary conditions changes the sign of the interaction from attraction to repulsion. Here we report first measurements where the amplitude of the surface field is systematically varied by controlling the surface properties of the confining surfaces. The Critical Casimir Forces are measured with total internal reflection microcopy between a single colloidal particle and a flat surface in a water - 2,6-lutidine mixture.