Concentration dependence of droplet deformation in a phase separation process under an electric field.

We show how deformation of droplets, arising in a phase separation process of a two-phase dielectric or conducting liquid composite material under a low frequency electric field, depends on their volume fraction. The electric interactions between distorted particles is taken into account in a self-consistent way based on the effective medium approach. It follows from our model that the main physical mechanism responsible for the dependence of droplets' deformation on the volume fraction is the formation of an effective anisotropic medium. A two-parameter condition of the droplet instability was derived as a function of the dielectric permittivity or conductivity mismatch between the two phases and the volume fraction of the inclusions.