Electrohydrodynamics of compound droplet in a microfluidic confinement

TL;DR

This study models the electrohydrodynamics of a compound droplet in microfluidic channels, revealing how electric fields and confinement influence droplet deformation and motion, with implications for biomedical applications.

Contribution

It introduces a phase field and asymptotic model to analyze the complex electrohydrodynamics of compound droplets under confinement, considering dielectric properties and eccentricity effects.

Findings

Shape deformation increases with confinement in perfect dielectric systems.

Inner droplet motion becomes translational and independent of electrical properties with increased confinement.

Eccentricity causes complex droplet motions depending on electrical properties.

Abstract

The present study deals with the dynamics of a double emulsion confined in a microchannel under the presence of a uniform electric field. Towards investigating the non-trivial electrohydrodynamics of a compound droplet, confined in between two parallel plate electrodes, a phase field approach has been adopted. Under the assumption of negligible fluid inertia and small shape deformation, an asymptotic model is also developed to predict the transient as well as the steady state droplet dynamics in the limiting case of an unbounded suspending medium. The phases involved are either assumed to be perfect dielectric or leaky dielectric. Subsequent investigation shows that shape deformation of either of the interfaces of the droplet increase with rise in the channel confinement for a perfect dielectric system. However, for a leaky dielectric system, the deformation of inner droplet and outer droplet can increase or decrease with the rise in channel confinement depending on the electric properties (conductivity and permittivity) of the system. The present study further takes into account the effect of eccentricity of the inner droplet. Depending on the relative magnitude of the permittivity and conductivity of the system, the inner droplet, if eccentrically located, may exhibit a to and fro or a simple translational motion. It is seen that increase in the channel confinement results in a translational motion of the inner droplet thus rendering its motion independent of any electrical properties. Since the compound droplet model approximately mimics the structure of a cell, the current investigation is expected to provide a significant impact towards predicting the effect of an externally imposed electrical field on the dynamics of a cell in any fluidic confinement and hence has the potential towards widespread applications in the field of medical diagnostics.