Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 16: Poster Session I

BP 16.15: Poster

Tuesday, March 27, 2007, 17:00–19:30, Poster D

Nanoscale thermophoresis for bioanalysis on a chip — •Christoph Wienken and Dieter Braun — Emmy Noether Group at the Center of NanoScience (CeNS),, Ludwig Maximilian Universität München, Amalienstrasse 54, 80799 Munich, Germany

We explored a chip-based all electrical measurement scheme for thermophoresis on the nanoscale. Thermophoresis, also called Soret effect, is the movement of particles in a temperature gradient. It is sensitive to the particles' properties like charge and size.[1] Previously, measurements were carried out all optical. But for simpler and cheaper detection we now use a all electrical setup. By miniaturizing the setup to nanoscale we significantly increased the speed of the measurement.

In the experiment both heating and concentration measurements are realized electrically. We use a very narrow, miniaturized gold/gold capacitor covered with a nanoliter droplet. Applying a high frequency AC voltage to the capacitor creates a temperature gradient between the capacitor and its environment by ohmic heating of the solution. Due to this gradient particles move out of the capacitor and result in a changed conductivity of the analyte. The latter is detected in the current signal.

Our simulations show that the analysis results are obtained within milliseconds, much faster than existing methods. This is due to the highly localized resistive heating near the capacitor. The chip-based layout doesn*t require any precisely applied volumina but only a millimetre-sized droplet which covers the sensitive area.

[1] Stefan Duhr and Dieter Braun, PNAS 103, 19678-19682 (2006)