Acceleration of polymer capture and translocation in oscillatory channels at certain frequencies.

Abstract

Elucidating the dynamic mechanisms of polymer translocation through nanochannels with channel oscillation characterized by periodic opening and closing is critical for advancing the understanding of polymer transport in confined environments and guiding the design of advanced nanofluidic systems. We employed coupled molecular dynamics and multi-particle collision dynamics simulations to investigate the influence of channel oscillation on polymer capture and translocation in varying dielectric environments. The capture probability and translocation time of polymers consistently exhibit a non-monotonic dependence on oscillation frequency. Translocation is accelerated within a certain range of the reduced oscillation frequency <i></i>, with the translocation time reaching a minimum in the interval of 10^-1 to 10⁰, where <i></i> is defined as the ratio of the translocation time through a static channel to the oscillation period. This interval corresponds to the regime where the oscillation period is commensurate with the timescale of polymer translocation. Analysis indicates that periodic opening and closing of the channel generates a microflow toward the trans side <i>via</i> hydrodynamic interactions, driving monomers into the channel during opening and facilitating their expulsion during channel closure, thereby accelerating capture and translocation. Furthermore, it modulates polymer conformation, enhancing the driving force on polymers and further promoting translocation. Conversely, electrostatic interactions impede these processes by altering polymer conformation and introducing steric hindrance from condensed counterions. These findings reveal fundamental mechanisms of polymer dynamics in oscillatory channels and may provide insights into systems where such dynamics are a key factor, from biological pores to the design of synthetic nanochannels.