Forced generation of simple and double emulsions in all-aqueous system

TL;DR

This paper introduces a simple, pressure-driven microfluidic method for producing monodisperse water-in-water and water-in-water-in-water emulsions, expanding droplet microfluidics to all-aqueous systems.

Contribution

The authors develop a novel pressure perturbation technique for generating all-aqueous emulsions, enabling controlled production of single and double emulsions without surfactants.

Findings

Successful generation of monodisperse water-in-water emulsions

Controlled production of water-in-water-in-water double emulsions

Potential for applying microfluidics to fully aqueous systems

Abstract

We report an easy-to-implement method that allows the direct generation of water-in-water (w/w) single emulsions. The method relies on direct perturbation of the pressure that drives the flow of the dispersed phase of the emulsions. The resultant inner jet is induced to break up into droplets due to the growth of the perturbation through Rayleigh-Plateau instability [L. Rayleigh, Proc. R. Soc. London 29, 71-97 (1879)]; this leads to the formation of monodisperse droplets. By implementing this method on a modified microfluidic device, we directly generate water-in-water-in-water (w/w/w) double emulsions with good control over the size and the number of encapsulated droplets. Our approach suggests a new route to apply droplet-based microfluidics to completely water-based systems.