Nonlinear electrohydrodynamics of a viscous droplet

A classic result due to G.I.Taylor is that a drop placed in a uniform electric field becomes a prolate or oblate spheroid, which is axisymmetrically aligned with the applied field. We report an instability and symmetry-breaking transition to obliquely oriented, steady and unsteady shapes in strong fields. Our experiments reveal novel droplet behaviors such as tumbling, shape oscillations, and chaotic dynamics even under creeping flow conditions. A theoretical model, which includes anisotropy in the polarization relaxation due to drop asphericity and charge convection due to drop fluidity, elucidates the interplay of interfacial flow and charging as the source of the rich nonlinear dynamics.