An electrohydrodynamic dance of unequal partners

Abstract

The dynamics of charge-free dielectric droplets under electric fields in weakly conducting fluids is relevant to a large range of technological and environmental applications. In Sorgentone & Vlahovska (J. Fluid Mech., vol. 951, 2022, R2), the authors investigate by asymptotic theory and boundary integral simulations the motility states of a pair of dissimilar droplets at an arbitrary orientation to the electric field and find a state of steady motility that is carefully balanced between repulsion and contact.

Nonequilibrium structure formation in electrohydrodynamic emulsions

“…Recent work has demonstrated that two dissimilar drops may undergo non-reciprocal EHD interactions, 27 via theoretical calculations 50 and boundary integral simulations. 51 While pairwise DEP interactions are always reciprocal, since the polarization of each drop contributes equally to the relative motion of the pair, hydrodynamic interactions due to the EHD flow depend only on the properties of the drop instigating the flow.…”

“…20,21 Observation of the individual and collective behavior of active drop systems can thus be difficult at long timescales, due to finite limitations in the fuel available. 27 Effort has also been made to design systems that undergo collective motion via external energy input, such as with electric and magnetic fields, [28][29][30][31][32] light, 33 or acoustics. 34 However, using external fields to drive force-free motion of drops, as opposed to rigid particles, has received less attention.…”

“…Non-reciprocal interactions have been observed in active droplet systems, 54 as well as in broader contexts, such as in neural networks 55 and social dynamics. 56 In EHD emulsions, the emergence of non-reciprocal interactions offer a promising alternative to fuel-limited active drop systems, 27 and thus it is of interest to analyze the collective dynamics that arise, which is the central goal of the present work. Notably, the works mentioned above focused on the combined EHD and DEP interactions between a pair of drops, with some extension to three and four drops.…”