Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Micro and Nano Fluidics III: Migration and flow

CPP 28.7: Vortrag

Donnerstag, 28. Februar 2008, 18:15–18:30, C 264

Fluid flow induced by temperature waves - a thermomechanical pumping mechanism for microfluidics — Franz M. Weinert¹, •Jonas A. Kraus², Thomas Franosch², and Dieter Braun¹ — ¹Applied Physics and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, Amalienstrasse 54, D-80799 München, Germany — ²Arnold Sommerfeld Center for Theoretical Physics (ASC) and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, Theresienstrasse 37, D-80333 München, Germany

Recently, flow at the scale of millimeters and below has attracted significant attention, stimulated by the rapid advances to manipulate and to control small-scale devices. Here, conventional pumping encounters major difficulties and a challenge of the field of microfluidics is to provide adequate tools for fluid manipulation at the microscale.

Here we propose a new mechanism that allows to generate net fluid flow by optical control. The thermal expansion of a fluid combined with a temperature-dependent viscosity introduces nonlinearities in the Navier-Stokes equations unrelated to the convective momentum current. With a suitable set-up we demonstrate that nonsteady heating can be employed to induce non-trivial flow patterns at small scales. This novel thermo-mechanical effect is investigated for a thin fluid chamber by a numerical solution of the Navier-Stokes equations and analytically by a perturbation expansion. A demonstration experiment confirms the basic mechanism and quantitatively validates our theoretical analysis.