(349f) Migration and Concentration of DNA within Microfluidic Channels

Pressure-driven flow of DNA solutions through a microchannel in the presence of a parallel electric field generates a net migration of DNA towards the walls. Over time a strongly inhomogeneous distribution of DNA develops in the channel, with almost all the DNA localized within 10 microns of the walls. Near the walls the electrophoretic velocity drives a return flux of DNA towards the inlet, and nearly all of the DNA remains trapped within the device despite an average fluid velocity that that exceeds the opposing electrophoretic velocity by at least ten times.

Experimental observations have provided unambiguous evidence that DNA migration occurs as outlined above, and that the migration is necessary for trapping. The mechanism inducing this DNA migration has been attributed to hydrodynamic interactions induced by the electric field. Migration due to viscoelasticity is another possibility, but a series of experiments systematically varying the viscoelasticity and ionic strength of the buffer solution demonstrate the electrically-induced flow, not the viscoelasticity, is the cause of the migration. However, both mechanisms may be operative in some systems. This migration mechanism can be used to not only concentrate, but also to purify, DNA within a simple microfluidic device.