Electrohydrodynamics of complex emulsions

Electrohydrodynamics of droplets immersed in an immiscible carrier fluid were first

explored in a pioneering paper by G. I. Taylor who formulated the weakly conducting or

leaky dielectric model and predicted the steady drop shape in the small-deformation

limit. Contemporary literature in electrohydrodynamic studies focuses primarily on the

deformations of single droplets. On the other hand, the collective behavior of many

droplets shows a wide range of surprising phenomena.

In the presence of a DC electric field, the electrokinetics at the interface of a drop

governs its deformations, and at higher field amplitudes, drives the system out of

equilibrium into multi-scale dynamical structures that resemble turbulent flow, even

though the system is at very low Reynolds number. In low-frequency AC fields,

electrohydrodynamics is frequency-tunable [1] and drop breakup is controllable enough

to produce roughly monodisperse emulsions. Three-fluid emulsions have been reported

recently [2], but these systems are athermal and highly polydisperse.

As most of the action is at the liquid-liquid interface, changing the complexity of the

emulsion can dramatically alter the dynamic behaviour to a new level. Working under

the hypothesis that electrohydrodynamics can be analogous to thermalizing the system,

this study experimentally examines the electrohydrodynamics of three-fluid emulsions.