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Light-Induced Dielectrophoretic Manipulation of DNA

Marco Hoeb ^*, Joachim O. Rädler , Stefan Klein , Martin Stutzmann ^* and Martin S. Brandt ^*

^* Walter Schottky Institut, Technische Universität München, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, München, Germany; and Institut für Photovoltaik, Forschungszentrum Jülich, Jülich, Germany

Correspondence: Address reprint requests to M. Hoeb, Tel.: 49-89-2891-2755; E-mail: hoeb{at}wsi.tum.de.

Light-induced dielectrophoretic movement of polystyrene beads and -DNA is studied using thin films of amorphous hydrogenated silicon as local photoaddressable electrodes with a diameter of 4 µm. Positive (high-field seeking) dielectrophoretic movement is observed for both types of objects. The absence of strong negative (low-field seeking) dielectrophoresis of DNA at high frequencies is in agreement with the similarity of the dielectric constants of DNA and water, the real part of the dielectric function. The corresponding imaginary part of the dielectric function governed by the conductivity of DNA can be determined from a comparison of the frequency dependence of the dielectrophoretic drift velocity with the Clausius-Mossotti relation.