Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 11: Micro- and Nanofluidics

BP 11.3: Talk

Tuesday, March 27, 2007, 16:30–16:45, H43

Light Driven Microfluidics — •Franz Weinert and Dieter Braun — Noether Group on Dissipative Biosystems, LM-University Munich, Amalienstr. 54, D-80799 Munich, Germany

Microfluidics will play a major role for complex liquid manipulation in a wide variety of biological and chemical applications of the life sciences. In conventional microfluidics, liquid is pumped and switched through lithographically defined channels. Such microfluidic chips have to connect to a considerable complex interface for pumping, switching and providing the liquids.

We present an all-optical fluid flow control, which allows highly flexible and dynamic liquid handling, both in microfluidic channels and twodimensional gels. The fluid follows the arbitrary shaped path of an infrared laser scanning microscope without the need for microfluidic tubings and valves.

The physics behind is thermal expansion in a viscosity gradient, an effect previously not considered. We derive an analytical solution for the pump speed directly from the Navier-Stokes equations. Thermal relaxation is on the millisecond time scale and allows fast repetition of the laser spot movement. Pump speed rises quadratically for decreasing thickness, making the mechanism perfectly suitable for Nanofluidics. Under moderate conditions, pump speeds are 20 µm/s in a 2.5 µm thin water film. Notably, highly viscous liquids can be equally pumped. The novel mechanism allows highly miniaturized microfluidics under dynamic control without predefined channels.