Non-coalescence phenomenon in leaky-dielectric emulsions: Formation of drop chains

Abstract

Formation of a chain of droplets in water–oil emulsions in the presence of an externally applied electric field has been attributed to the formation of tiny, non-coalescing satellite droplets between the droplets. Such chains have also been observed in leaky-dielectric emulsions where the conductivity ratio of the constituent fluids is of the same order. In the present article, we show that the droplet chain can also form in such systems by entrapment of a thin film of the ambient fluid between the droplets. We draw a phase map based on electrical conductivity and permittivity ratios, showing different scenarios of droplet–droplet interactions, namely, coalescence, non-coalescence with drops forming a thin film, and drops drifting apart.