Electrophoresis of deformable polyelectrolytes in a nanofluidic channel.

ABSTRACT

The influence of the shape of a polyelectrolyte (PE) on its electrophoretic behavior in a nanofluidic channel is investigated by considering the translocation of a deformable ellipsoidal PE along the axis of a cylindrical nanochannel. A continuum model comprising a Poisson equation for the electric potential, Nernst-Planck equations for the ionic concentrations, and modified Stokes equations for the flow field is adopted. The effects of the PE shape, boundary, bulk ionic concentration, counterion condensation, electroosmotic retardation flow, and electroosmotic flow (EOF) on the PE mobility are discussed. Several interesting behaviors are observed. For example, if the nanochannel is uncharged and the double layer is thick, then the PE mobility increases (decreases) with increasing double-layer thickness for a smaller (larger) boundary, which has not been reported previously. If the nanochannel is negatively charged and the double layer is thick, then a negatively charged PE moves in the direction of the applied electric field. The results gathered provide necessary information for both the interpretation of experimental data and the design of nanochannel-based sensing devices.