Friday, 21 July, 2006
Optothermal Molecule Trapping by Opposing Fluid Flow with Thermophoretic Drift
Stefan Duhr and Dieter Braun -
Phys. Rev. Lett. 97, 038103 (2006)
Thermophoresis moves molecules along temperature gradients, typically from hot to cold. We superpose fluid flow with thermophoretic molecule flow under well-defined microfluidic conditions, imaged by fluorescence microscopy. DNA is trapped and accumulated 16-fold in regions where both flows oppose each other. Strong 800-fold accumulation is expected, however, with slow trapping kinetics. The experiment is equally described by a three-dimensional and one-dimensional analytical model. As an application, we show how a radially converging temperature field confines short DNA into a 10 µm small spot.