Transport-induced-charge (TIC) phenomenon originating from local charge imbalance due to the presence of a non-uniform electric field occurs ubiquitously in nanopore systems. When an electrolyte concentration gradient and an electric field are simultaneously imposed across a nanopore, the resultant TIC phenomenon gives rise to unique electroosmotic behavior. Previous numerical simulation results have shown that this TIC electroosmosis is subject to bulk conditions, independent of nanopore surface charge properties, providing an effective method to precisely control electroosmosis in nanopores. However, these continuum studies based on the mean field theory ignore atomistic properties and ionic steric effects, which are of great importance in tiny scales. In this study, we employ molecular dynamics simulation to investigate TIC concentration and TIC electroosmotic behavior in silica nanopores filled with potassium chloride aqueous solutions. When a concentration gradient is applied in the same direction with the external electric field, negative charges are locally induced inside the nanopore, yielding a higher nanopore selectivity for anions. These simulation results show quantitative agreement with analytical predictions, shedding light to non-linear electrokinetic behavior in ultrathin nanopores.

Transport-induced-charge phenomenon

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