Interfacial transport with mobile surface charges and consequences for ionic transport in carbon nanotubes
Laboratoire de Physique Statistique, UMR CNRS 8550, Ecole Normale Supérieure, PSL Research University, 24 rue Lhomond, 75005, Paris, France
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Accepted: 30 November 2018
Published online: 19 December 2018
In this paper, we explore the effect of a finite surface charge mobility on the interfacial transport: conductance, streaming currents, electro- and diffusio-osmotic flows. We first show that the surface charge mobility modifies the hydrodynamic boundary condition for the fluid, which introduces a supplementary term depending on the applied electric field. In particular, the resulting slip length is found to decrease inversely with the surface charge. We then derive expressions for the various transport mobilities, highlighting that the surface charge mobility merely moderates the amplification effect of interfacial slippage, to the noticeable exception of diffusio-osmosis and surface conductance. Our calculations, obtained within Poisson-Boltzmann framework, highlight the importance of non-linear electrostatic contributions to predict the small concentration/large charge limiting regimes for the transport mobilities. We discuss these predictions in the context of recent electrokinetic experiments with carbon nanotubes.
Key words: Flowing Matter: Interfacial phenomena
© EDP Sciences, SIF, Springer-Verlag GmbH Germany, part of Springer Nature, 2018