(209j) The Effect of Long-Range Hydrodynamic Interactions on the Anomalous Migration of DNA in Micro-Capillaries

Simultaneously applying an electric field in the same, or opposite, direction of a pressure gradient causes DNA to migrate perpendicularly to the fields during transport through a capillary tube. Migration is predicted to arise from the electrically induced hydrodynamic interactions between the segments of the DNA, which is distorted from an equilibrium configuration due to the shearing flow. We have measured the migration in detailed experiments in which the ionic strength of the solution and the strengths of the electric and flow fields have been varied. The migration is confirmed to exist, supporting the hypothesis that long-range interactions due to the electric field are not fully screened. Comparisons are made of the measured migrations with the migrations predicted by theory and simulation. Application of parallel fields in microfluidic devices can lead to advanced separation methods and enhanced adsorption techniques.