Chain models for the simulation of polyelectrolytes in combination of flow and electric fields

Combined Poiseuille flow and electric fields have been used to drive transverse migration of charged polyelectrolytes in channels with use in separation of DNA. But the migration is not monotonic in electric field strength. Previously a simple dumbbell model has been used to understand the mechanism for this non-monotonic trend. Migration can alter polymer conformations which then alters migration. The dumbbell model qualitatively captured some experimental behavior but may not be accurate for strong electric fields. We use chain models to overcome this problem. A combination of theoretical calculations and Brownian Dynamics simulations is used. Two different ways of calculating electrophoretic mobility are considered. Firstly we treat the polymer as having a single (average) mobility. Then we consider the individual springs as having unique mobilities. For average mobility, simulations are consistent with the mechanism found for the dumbbell model. Allowing springs to move with unique mobilities introduces additional mechanism for electric field to alter polymer conformations and migration. By using chain models, we expect to gain further insight into the interplay between migration and conformation for strong electric fields.