Electrophoretic Mobility of Polyelectrolytes within a Confining Well

TL;DR

This study uses simulations to show that polyelectrolyte electrophoretic mobility increases under nanoconfinement due to segment orientation within Debye layers, revealing new insights into confined polymer dynamics.

Contribution

It demonstrates that confinement enhances electrophoretic mobility through segment orientation, despite hydrodynamic screening, a novel finding in polyelectrolyte behavior under confinement.

Findings

Mobility increases with confinement in nanoconfining wells.

Segment orientation within Debye layers is the primary mechanism.

Length-dependent mobility arises from counterion condensation effects.

Abstract

We present a numerical study of polyelectrolytes electrophoresing in free solution while squeezed by an axisymmetric confinement force transverse to their net displacement. Hybrid multi-particle collision dynamics and molecular dynamics simulations with mean-field finite Debye layers show that even though the polyelectrolyte chains remain "free-draining", their electrophoretic mobility increases with confinement in nanoconfining potential wells. The primary mechanism leading to the increase in mobility above the free-solution value, despite long-range hydrodynamic screening by counterion layers, is the orientation of polymer segments within Debye layers. The observed length-dependence of the electrophoretic mobility arises due to secondary effects of counterion condensation related to confinement compactification.