Effect of the difference in ion mobilities on traveling-wave electro-osmosis

TL;DR

This paper investigates how differences in ion mobilities affect traveling-wave electro-osmosis in aqueous solutions, providing a mathematical analysis of velocity dependence on frequency, wavelength, and voltage amplitude.

Contribution

It introduces a detailed model accounting for ion mobility differences in AC electro-osmosis, analyzing both slight and strong asymmetries in ion mobilities.

Findings

Velocity depends on ion mobility differences and applied frequency.

Distinct behaviors observed for symmetric and asymmetric ion mobility cases.

Mathematical framework established for predicting electro-osmotic flow characteristics.

Abstract

We analyze the AC electro-osmotic motion of a 1:1 aqueous solution, taking into account the difference in mobilities and diffusion coefficients between positive and negative ions. This model serves to understand the behavior of common systems as a solution of NaCl in water. We pay special attention to two cases. First, the case of slightly different mobilities, that can model a KCl solution. Second, the case of a strongly asymmetric solution, with an almost vanishing mobility, applicable to the case of a salt where the negative ion is much more massive than the positive one. For all the cases, we perform the mathematical description and linear analysis of the problem, in order to establish the dependence of the induced velocity with the frequency, wavelength and amplitude of the applied voltage.