Liquid friction on charged surfaces: from hydrodynamic slippage to electrokinetics

TL;DR

This paper uses Molecular Dynamics simulations to explore how electric charges on surfaces influence liquid friction and electrokinetic effects, revealing potential for enhanced microfluidic applications.

Contribution

It introduces a detailed analysis of electric contributions to liquid friction on charged surfaces and their impact on electrokinetic phenomena, expanding understanding of hydrodynamic boundary conditions.

Findings

Electric surface charge significantly affects liquid friction.

Strong amplification of electro-osmotic effects observed.

Potential to create giant electrokinetic effects for microfluidics.

Abstract

Hydrodynamic behavior at the vicinity of a confining wall is closely related to the friction properties of the liquid/solid interface. Here we consider, using Molecular Dynamics simulations, the electric contribution to friction for charged surfaces, and the induced modification of the hydrodynamic boundary condition at the confining boundary. The consequences of liquid slippage for electrokinetic phenomena, through the coupling between hydrodynamics and electrostatics within the electric double layer, are explored. Strong amplification of electro-osmotic effects is revealed, and the non-trivial effect of surface charge is discussed. This work allows to reconsider existing experimental data, concerning Zeta potentials of hydrophobic surfaces and suggest the possibility to generate ``giant'' electro-osmotic and electrophoretic effects, with direct applications in microfluidics.