Electroviscous drag on squeezing motion in sphere-plane geometry

Theoretically and experimentally, we study electroviscous phenomena resulting from charge-flow coupling in a nanoscale capillary. Our theoretical approach relies on Poisson-Boltzmann mean-field theory and on coupled linear relations for charge and hydrodynamic flows, including electro-osmosis and ch...

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Bibliographic Details
Published in:arXiv.org 2022-05
Main Authors: Marcela Rodriguez Matus, Zhang, Zaicheng, Benrahla, Zouhir, Majee, Arghya, Maali, Abdelhamid, Würger, Alois
Format: Article
Language:English
Subjects:
Charge density
Coupling
Drag coefficients
Electroosmosis
Film thickness
Laminar flow
Mean field theory
Parameters
Surface charge
Water film
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Summary:Theoretically and experimentally, we study electroviscous phenomena resulting from charge-flow coupling in a nanoscale capillary. Our theoretical approach relies on Poisson-Boltzmann mean-field theory and on coupled linear relations for charge and hydrodynamic flows, including electro-osmosis and charge advection. With respect to the unperturbed Poiseuille flow, we define an electroviscous coupling parameter \(\xi\), which turns out to be maximum where the film thickness \(h_0\) is comparable to the screening length \(\lambda\). We also present dynamic AFM data for the visco-elastic response of a confined water film in sphere-plane geometry; our theory provides a quantitative description for the electroviscous drag coefficient and the electrostatic repulsion as a function of the film thickness, with the surface charge density as the only free parameter. Charge regulation sets in at even smaller distances.
ISSN:2331-8422
DOI:10.48550/arxiv.2201.01022