Konwersatorium im. Leopolda Infelda

I will describe recent microfluidics experiments using DNA as a model polyelectrolyte. The DNA is introduced into the channel by a pressure driven flow, and simultaneously subjected to an axial electric field.
Epifluorescent and confocal microscopy have been used to show that, under opposing fields, the DNA migrates to the walls of the microfluidic channel. An interesting consequence is that DNA then rapidly accumulates near the channel inlet, suggesting a possible means to both concentrate and purify DNA.

Unlike a number of electrokinetic-based separations, the trapping of the DNA does not depend on complex flows or fields. Rather, it exploits (we think) a little studied aspect of polyelectrolytes; namely that an electric field can generate a long-range (1/r^3) flow around the molecule. When combined with symmetry breaking, induced (for example) by a shear flow, this leads to novel length-dependent motions of the polymer.

In this talk I will summarize the results of our experiments, present the outline of a theory to describe the migration, and suggest possible biotechnology applications.