Droplet electromigration beyond the Taylor-Melcher model explained through the strong-electrolyte limit

The control of fluid droplets inside a microfluidic system relies heavily on the predictability of their behavior in the presence of electric fields. Traditional models, such as the Taylor-Melcher model, capture electromigration observed in experimental studies only under certain conditions.

In the presented work, electromigration of immiscible droplets in strong electrolytes is investigated by an asymptotic approach¹ resolving the nonlinear Debye-layer electrokinetics. Quantitative predictions on migration speed and deformation of the drop are made. In accordance with previous theoretical and experimental studies, the occurrence of electromigration is confirmed. The influence of material parameters is discussed. Remarkably, migration phenomena appear even for droplets with zero net charge. In such systems, the influence of electrolyte strength is found to be small. Other modeling parameters, e.g. approximation of the drop geometry, can be of major impact.

A comparison to existing electrohydrodynamic and electrokinetic models is presented.



References:

¹Marthaler, Philipp G., and Class, Andreas G. "Weak curvature asymptotics for Debye layers as electrohydrodynamic discontinuities." Physical Review E 105.3 (2022): 035106.