Dresden 2006 – scientific programme

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SYSS: Structure Formation and Self-Organization in non-equilibrium Systems

SYSS 1: Structure Formation and Self-Organization in non-equilibrium Systems I

SYSS 1.2: Talk

Thursday, March 30, 2006, 09:45–10:00, BAR Sch\"o

Structure Formation by Heat - understanding and applying Thermophoresis — •Stefan Duhr, Franz Weinert, and Dieter Braun — Noether Group on Dissipative Microsystems, Applied Physics, Ludwig Maximilians Universität München, Amalienstr. 54, 80799 München, Germany

Molecules typically move from hot to cold in temperature fields, a non-equilibrium effect called thermophoresis. Compared to electrophoresis, temperatures can be applied with micrometer resolution in microfluidics, yielding an alternative to electrophoresis for biomolecule analysis. Until recently, however, theoretical understanding was poor. We report on:

o Thermophoresis of DNA and polystyrene beads is driven by solvation entropy, shown by novel microfluidic fluorescence measurements.As a result, the effective charge of molecules is inferred more robust and simple than from electrophoresis.

o Nonlinear thermophoresis reveals deviations from the Onsager foundation of thermophoresis due to a breakdown of the local equilibrium assumption. Only then, thermophoresis across a solid-water interface can crystallize colloids.

o DNA is accumulated by flow in microfluidics. Giant accumulation driven by convection is predicted for single nucleotides near volcanic seafloor vents, closing missing links in molecular evolution of life

o Water can be pumped with an infrared laser scanning microscope as a result of nonlinear thermal expansion. It allows to shrink thermophoretic field flow fractionation to microfluidic dimensions.

Website: http://www.biophysik.physik.uni-muenchen.de/Braun