Single-DNA-molecule trapping with silicon nanotweezers using pulsed dielectrophoresis

Abstract

DNA manipulation based on dielectrophoresis between microfabricated electrodes is one of the most efficient methods for the physical handling of molecules. Dielectrophoresis is routinely used for stretching and trapping DNA molecules between the opposing tips of silicon nanotweezers. However, the precise number of trapped molecules is difficult to predict, as a continuous application of ac voltage continually attracts the molecules while the electric-field-induced fluid flow prevents them from bridging the tips. To circumvent this difficulty, the dielectrophoresis signal is applied during very short intervals. In this pulsed mode, the electrohydrodynamic fluid flow is lessened and the molecule trapping success rate is greatly enhanced. A fluorescently labeled single λ-DNA molecule was successfully stretched and captured by the silicon nanotweezers with 50 ms pulses of a 1 MHz, 1 MV m-1 ac dielectrophoresis voltage. This single-molecule trapping between the tweezers' tips is monitored, in real time, under fluorescence imaging. © 2011 IOP Publishing Ltd.