Dumbbell model for the simulation of polyelectrolytes in combination of flow and electric fields

The combination of Poiseuille flow and electric fields has been used to drive the transverse migration of charged polyelectrolytes in channels, resulting in non-uniform concentration profiles. Manipulation of these profiles can be used to drive separations of charged polyelectrolytes such as double stranded DNA. Interestingly, the amount of migration is not monotonic in electric field strength. Rather the migration peaks at intermediate electric fields before decreasing. To date, the mechanism for this non-monotonic trend has been poorly understood as prior models have been unable to reproduce this behavior. To gain insight to the underlying phenomena, we used a combination of theoretical calculations and Brownian Dynamics simulations in order to understand the mechanism of migration and why it results in a non-monotonic trend. It was found that at high electric field strengths, the migratory flux of polymers was able to impact the conformational distribution, altering the electrophoretic mobility and, in turn, limiting the migration. Further, when comparing to experimental migration data, our model captures the position of the maximal migration with near quantitative accuracy.