Modulation of Electroosmotic Flow through Short Nanopores by Charged Exterior Surfaces

TL;DR

This study uses simulations to show how charged exterior surfaces of short nanopores can significantly enhance electroosmotic flow, providing insights for optimizing nanoporous membrane design in nanofluidic applications.

Contribution

It introduces a quantitative analysis of how exterior surface charges modulate EOF, including the effective width parameter and its dependence on various physical factors.

Findings

Charged exterior surfaces increase EOF velocity and pressure.

The effective width Lcs_eff scales with pore diameter, charge density, and voltage.

Lcs_eff decreases with pore length and salt concentration.

Abstract

Electroosmotic flow (EOF) through nanoporous membranes has broad applications in micro- and nanofluidic systems, particularly in biomedical diagnostics and chemical analysis. The use of short nanopores enables high fluid flux, and the presence of exterior surface charges can further enhance ion flux through short nanopores. Here, systematic simulations are conducted to explore the modulation of EOF by exterior surface charges. Our results indicate that charged exterior surfaces can provide an additional effective pathway for fluid flow, significantly increasing both the EOF velocity and output pressure. By analyzing the dependence of EOF velocity on the area of the charged exterior surface, we derive the effective width (Lcs_eff) of the charged ring region extending beyond the pore boundary. This parameter is quantitatively examined under various nanopore configurations and applied conditions. Lcs_eff is found to be proportional to the pore diameter, surface charge density, and applied voltage, while inversely proportional to pore length and salt concentration. These findings provide valuable insights into the modulation of EOF by exterior surface charges and offer theoretical guidance for optimizing the structural and functional properties of nanoporous membranes in practical applications of EOF.