Flow-induced surface charge heterogeneity in electrokinetics due to Stern-layer conductance coupled to reaction kinetics

TL;DR

This paper presents a theoretical analysis of electrokinetic flow in charged channels, revealing how Stern-layer conductance and dynamic surface charge regulation lead to heterogeneous surface charges and complex electric flux patterns, explaining experimental observations.

Contribution

It introduces a novel theoretical framework that couples Stern-layer conductance with charge regulation, uncovering new steady states and heterogeneity in electrokinetic flows.

Findings

Flow induces heterogeneous surface charge and zeta-potential.

Identification of a new steady state with 3D electric flux.

Explanation of flow effects on interfacial chemistry in experiments.

Abstract

We theoretically study the electrokinetic problem of a pressure-induced liquid flow through a narrow long channel with charged walls, going beyond the classical Helmholtz-Schmolukowski picture by considering the surprisingly strong combined effect of (i) Stern layer conductance and (ii) dynamic charge-regulating rather than fixed surface charges. We find that the water flow induces, apart from the well-known streaming potential, also a strongly heterogeneous surface charge and zeta-potential on chemically homogeneous channel walls. Moreover, we identify a novel steady state with a nontrivial 3D electric flux with 2D surface charges acting as sources and sinks. For a pulsed pressure drop our findings also provide a first-principles explanation for ill-understood experiments on the effect of flow on interfacial chemistry [D. Lis et al., Science 344, 1138 (2014)].