Electro-hydrodynamics study of double emulsion droplet formation in a double Y-shaped channel

Abstract

Although there have been more studies on droplet formation under the control of electrostatic field in recent years, the studies on the relationship between composite droplet formation and electrostatic field are fragmented. In order to analyze the effect of electrostatic field on composite droplet formation, this paper numerically investigates the electro-hydrodynamics of the double emulsion in a double Y-shaped microchannel and experimentally verifies the applied phase interface capture method. Calculations are carried out using a model coupled with the phase field method and electrostatic field to analyze the interfacial evolution of double emulsions under different electric field strengths and to quantitatively study the droplet formation process. Four flow regimes different from previous studies were found: dripping regime, jetting regime, threading regime, and jetting-dripping transition regime, among which the formation frequency ( f ) of double emulsion droplets under the short jetting regime was up to 769 Hz. The eccentricity (ε) of droplets under the dripping regime was the smallest, with ε of 0.2, the coefficient of deformation (Defm) of the middle phase droplets was minimized to 0.05. It is observed that there is a linear relationship between Cam/Cao and CaE in the dripping regime, with the generation of multi-core double emulsion droplets. When Cam/Cao is greater than 14, the flow regime of the double emulsion in the channel is always threading regime, no matter how CaE is changed.