Effect of flagella like surface heterogeneity on the motion of charged macromolecules in the fibrous pore

Abstract

Motion of a charged particle inside an electrolyte lled uncharged channel is hindered due to hydrodynamic e ect and electrokinetic e ects. Presence of an obstacle on wall surface increases the drag force on the particle and reduces the particle velocity. Flagellum like obstacle tends to shift the particle away from the center. When any or both the particle and agellum are charged di erent electrokinetic phenomena like repulsion, relaxation, electrical double layer overlap a ect the drag force on the particle. Electrostatic repulsion always force the particle away from the agellum if both the particle and agellum are similarly charged and vice versa. Distortion of electric double layer causes relaxation which always tends of increase the drag force in ow direction. Double layer overlap also a ects the drag by redistributing the charge concentration. A nite element model consisting of Navier-Stokes, Pois- son and Nernst-Plank equation has been developed to quantify the e ect of such parameters on particle drag force. It is found that presence of agellum hydrody- namically tends to o center the particle at agellum upstream and later brings it back. Relaxation more prominently a ects electrical drag force than electrostatic repulsion and increases the drag force on the stationary particle in ow direction. With the decrease of separation distance both the hydrodynamic and electrical drag force increase. Solution concentration has signi cant e ect on the drag force. With the increase of concentration electrical drag force increases signi cantly due to in- creased surface charge on the particle surface resulting in higher total drag force. Drag factor has been found to be higher for charged particle than uncharged one. This excess drag is also increases with solution concentration.