AC electrokinetic manipulation of DNA

Abstract

The controlled manipulation of molecules is a crucial prerequisite for the emerging field of molecular nanotechnology. AC electrokinetics provide a powerful mechanism for both positioning and inducing conformational changes in molecules. In this paper, we investigate the elongation of fluorescently-labelled DNA strands, which are covalently tethered by one end to gold microelectrodes arranged in an opposing-finger geometry, when exposed to strong ac electric fields. We found that the elongation of the DNA molecules is restricted by the geometry of the gap, and that the observed contour of the elongated DNA molecules coincides with the electric field line pattern. Further, we discuss a potential elongation mechanism and provide evidence that the major contribution to the elongation originates from the ac electrokinetic torque, which is supplemented by a small bias force provided by the electric-field-induced fluid flow.