  Fluidic interfaces disintegrate under sufficiently strong electric fields,
leading to electrohydrodynamic (EHD) tip streaming. Taylor cones, which emit
charged droplets from the tip of a conical cusp, are among the most prominent
and well-studied examples of EHD instabilities. In liquid-liquid systems, more
complex interface deformation modes than simple Taylor cones can be observed,
with the interface being pushed away from the electrode, and additional cone
structures emerging from the rim of the dimple. In this article, we investigate
the mechanisms behind these deformation modes experimentally and numerically,
and demonstrate that the presence of droplets triggers the dimple at the
interface. In order to characterize the underlying processes, we replace the
pin electrode by a hollow metallic needle with a prescribed electrolyte volume
flow. The submerged electrospray introduces droplets of an aqueous KCl solution
with varying ion concentrations into silicone oils with varying viscosities. By
measuring the corresponding electric current and by optical investigation of
the interface deformation, we study the system response to variations of the
ionic concentration, viscosity, applied voltage as well as flow rate. In
addition to the experiments, we use a finite element solver and compute the
charge transport due to the droplets in the oil phase. Further, we compute the
electric potential distribution, flow field and interface deformation. After
calibration of our model with particle tracking velocimetry data of the flow
inside the oil phase, we reproduce the experimentally observed dimple at the
liquid-liquid interface. In summary, this work highlights the importance of
charged droplets for the complex dynamic modes observed when a liquid-liquid
interface is exposed to a local electric field.
