Electric Field-Induced "Tentillar" Bridging of a Droplet Twin.

Experimental investigations with high-speed imaging reveal that two unequal sized oppositely charged droplets suspended in an insulating oil can come in contact in an asymmetric manner under an electric field. The approaching poles of the droplets undergo asymmetric "cone-cone" to "cone-groove" deformations during noncoalescence under an electric field. Nonlinear three-dimensional simulations confirm the occurrence of a third "groove-groove" configuration at close proximity. A general linear stability analysis confirms the cone-cone to cone-groove transitions of the oil-water interfaces with decreasing thickness of the oil film. Experiments together with simulations confirm the bifurcation of the Taylor cone on the smaller droplet into a number of liquid "tentilla" bridges prior to contact with the bigger droplet. Simulations also predict that the length scales of the formation of such tentillar bridges from the initial Taylor cone match well with the predictions from the nonlinear bifurcation theory.