Influences of Electroosmotic Flow on Ionic Current through Nanopores: a Comprehensive Understanding

Abstract

Continuum simulations become an important tool to uncover the mysteries in nanofluidic experiments. However, fluid flow in simulation models is usually unconsidered. Here, systematical simulations are conducted to provide a quantitative understanding of influences from electroosmotic flow (EOF) on ionic transport through nanopores by both types of models with and without consideration of EOF. In nanopores of less than ~10 nm in diameter, counterions dominate ionic current which is always promoted obviously by the convective effect of EOF. In the diameter range from ~10 to ~30 nm, strong EOF induces ion concentration polarization or ion depletion inside nanopores which causes significant decreases in ionic current. For nanopores larger than ~30 nm, due to convective promotion and inhibition of EOF on the transport of counterions and anions, considerable nanopore selectivity to counterions maintains in cases with EOF. Though the difference in total current between both cases decreases with further pore size increasing, the difference in cation/anion current is still considerable. From our results under various pore parameters and applied conditions, the fluid flow should be considered in the simulation cases when EOF is strong. Our work may provide useful guidance for simulation conductance.