Wettability Modulated Charge Inversion and Ionic Transport in Nanofuidic Channels

TL;DR

This study explores how substrate wettability influences charge inversion and ionic transport in nanofluidic channels, revealing complex interactions that affect electrostatic behavior and current flow, with implications for biophysics and nanodevice design.

Contribution

It demonstrates that surface hydrophobicity can decrease interfacial potential and cause charge inversion at low surface charges, challenging previous assumptions.

Findings

Wettability affects charge inversion in nanochannels.

Interfacial hydrodynamics can reverse streaming currents.

Results supported by simulations and experiments.

Abstract

We unveil the role of substrate wettability on the reversal in the sign of the interfacial charge distribution in a nanochannel in presence of multivalent ions. In sharp contrast to the prevailing notion that hydrophobic interactions may trivially augment the effective surface charge, we demonstrate that the interplay between surface hydrophobicity and interfacial electrostatics may result in a decrease in the effective interfacial potential, and a consequent charge inversion over regimes of low surface charges. We also show that this phenomenon, in tandem with the interfacial hydrodynamics may non-trivially lead to either augmentation or attenuation or even reversal of the net streaming current, depending on the relevant physical scales involved. These results, supported by Molecular Dynamics simulations and experimental data, may bear far ranging consequences in understanding complex biophysical processes and designing nanofluidic devices and systems involving multivalent counterions.