Fluid rings and droplet arrays via rim streaming

TL;DR

This paper introduces a novel electrohydrodynamic instability at the equator of a drop in an electric field, creating fluid rings that break into uniform microdroplets, offering a new method for microemulsion production.

Contribution

It reports a new rim streaming mechanism driven by interfacial instability at the stagnation line in electric fields, distinct from tip streaming.

Findings

Formation of concentric fluid rings around the drop

Breakup of rings into monodisperse microdroplets

Identification of interfacial instability as the driving mechanism

Abstract

Tip-streaming generates micron- and submicron- sized droplets when a thin thread pulled from the pointy end of a drop disintegrates. Here, we report streaming from the equator of a drop placed in a uniform electric field. The instability generates concentric fluid rings encircling the drop, which break up to form an array of microdroplets in the equatorial plane. We show that the streaming results from an interfacial instability at the stagnation line of the electrohydrodynamic flow, which creates a sharp rim. The flow draws from the rim a thin sheet which destabilizes and sheds fluid cylinders. This streaming phenomenon provides a new route for generating monodisperse microemulsions.