UC Berkeley

Understanding ion transport through nanopores provides a central basis in advancing the design of molecular sensors or the preparation of biomimetic systems. Here we report a continuum modeling approach that introduces an alternating current field to investigate the competition between a surface-charge dominated electromigration process under a frequency induced ion dynamics at nanoscales. We highlight a transition from a surface-charge-dominated effect, where electric double layer impacts prevail, to bulk-like ion dynamics as pore dimensions approach the microscale. Results reveal that rapid electromigration dominates ion distribution at a millisecond time scale, generating transient, non-equilibrium concentration profiles. In contrast, lower frequency perturbations enable diffusion to equilibrate ion distributions within each cycle, establishing periodic quasi-steady states. The findings from this work highlight the interplay of ion selectivity and distribution by exploiting the dynamic competition between electromigration and diffusion in oscillating bias systems.