Regensburg 2010 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 20: Phase Transitions and Critical Phenomena I
DY 20.6: Talk
Wednesday, March 24, 2010, 15:45–16:00, H47
Critical Casimir forces under external control — •Ursula Nellen1, Laurent Helden1, and Clemens Bechinger1,2 — 12. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — 2Max-Planck-Insitut für Metallforschung, Heisenbergstr. 3, 70563 Stuttgart
That a confinement of critical fluctuations exerts a force on the boundaries was predicted by Fisher and de Gennes in 1978. However the first direct measurement of these critical Casimir forces could be obtained only recently [1]. Beside their exquisite temperature dependence critical Casimir forces respond to external fields. Here we study the variety of control parameters opening up novel perspectives for e.g. self assembly of colloidal particles or microfluidic systems. Using total internal reflection microscopy (TIRM) we measure forces acting on a colloidal particle suspended in a critical water-2,6-lutidine mixture. We demonstrate how a continuous variation in the chemical surface properties changes amplitude and sign of the critical Casimir force [2]. From temperature scans the scaling behavior for weak surface fields can be extracted. In addition we explore how critical Casimir forces can be influenced by external electric fields.
[1] C. Hertlein et al., Nature 451 (2008) 172,
[2] U. Nellen et al., EPL 88 (2009) 26001