Electric Field Induced Flow Fractionation in a Microchannel with Moving Walls and Hydrodynamic Slippage

The electric field flow fractionation (EFFF) technique is analyzed in the reporting study for the separation of DNA molecules based on their sizes inside a channel of micrometer scale where the influence of wall slip cannot be ignored. The upper wall of the microchannel moves in the same direction to that of the flow, whereas, the lower microchannel wall moves either in the same or in the opposite direction. Moreover, the magnitude of the lower wall velocity is either equal to or half of the upper wall velocity. The coupling of an axial pressure gradient and a lateral electric field is considered. The momentum and the convection–diffusion equations have been solved analytically along with suitable boundary conditions to obtain the expressions of the mean velocity and that of the universal dispersion function of the pulse of DNA molecules in dimensionless form. The pressure gradient shows an incrementing effect on the mean velocity irrespective of the nature of the wall motions. However, the slip length shows an incrementing effect on the mean velocity when the directions of wall motions are the same and a decrementing effect when the directions of wall motions are different. The pressure gradient shows a decrementing influence on the universal dispersion function except the case when the walls of the microchannel moves with the same magnitude and direction. Furthermore, the wall slip has a decrementing influence on the universal dispersion function except the case when the wall velocities are of the same magnitude and direction, where the dispersion becomes invariant with the slip length.