Electrodynamics of DNA Molecules Moving Through Microfluidic Channels Studied with Single Molecular Fluorescence Imaging Technology

Flow dynamic features of single DNA molecules moving within micro/nano-channels have become significant for they can be widely used in stretching, separation and development of high-speed DNA molecules sequencing technology. In this study, the electrodynamics' properties of lambda-DNA molecules which were transferred through microfluidic channels and driven by electric field force, were studied using single molecule fluorescence imaging technology. Results indicated that the velocity of DNA molecules moving within the microfluidic channels was critically dependent on the value of applied electric field, and their direction was commonly opposite to the direction of electric field. A particularly intriguing phenomenon was that the direction of DNA molecules moving within the 30 mu m channels was reversed at a threshold voltage, i.e., E-0 = 7 x 10(3) V/m, which was induced by competition between the electrophoresis effects and elecroosmosis. The microfluidic mechanisms were finally discussed.