Behavior of oblately deformed droplets in an immiscible dielectric liquid under a steady and uniform electric field

The deformation and breakup of droplets in a steady and uniform electric field were experimentally investigated. Droplets of silicone oil suspended in more electric-conducting caster oil undergoes the three following modes of deformation when subjected to an electric field: oblate deformation with a symmetric axis oriented close to parallel with the electric field, oblate deformation with a symmetric axis oriented obliquely to the electric field, and an oscillatory oblate–prolate deformation synchronized with a sit-up motion. Each droplet during the oscillatory motion is simultaneously observed from two directions, and the flow in the droplet is visualized by a tracer particle method. The oscillatory motion is revealed to involve electrorotation of the droplet. The conditions under which each of the three deformation modes or droplet breakup occurs are identified.