Effect of charged membrane on the particle motion through a nanopore

Electrophoretic motion of charged particles through a nanopore located in a membrane is numerically studied. The multi-ion model consisting of mass, charge, and momentum conservation equations is used to solve ionic concentration, velocity, pressure and electric fields. For membrane is charged, electroosmotic flow (EOF) is resulted when an external potential is applied. The electric and flow fields suggest that the particle driven by the electrophoretic force may move in a stationary fluid, in a direction opposite to the EOF, or in the same direction as the EOF, depending on the type and magnitude of the membrane charge. Particle suspended in the electrolyte may or may not travel to the pore, depending on the coupled effects between intensified electric field and EOF in the region near the pore. Moreover, charged membrane can modify the current as particles travel through the pore, either decrease or increase as compared with uncharged membrane. Our numerical results show that relative current change is significant if the particle size is comparable to pore size. For smaller particles, relative current change is negligible indicating that it is difficult to detect the small particle from the current change.