On the theory of the noncoalescence effect for oppositely charged droplets

A theory is proposed and numerical simulation is conducted for oppositely charged mutually approaching droplets of an aqueous electrolytic solution in silicon oil. It is shown that at small distances between droplets, a conductive bridge leveling out the potentials of the droplets may form between them due to electrohydrodynamic instability of the equilibrium surface of one of the droplets. As a result, the droplets start to repel each other and may drift apart without coagulation. The proposed theory is confirmed by the effect of nonconfluent droplets observed in experiments W.D. Ristenpart, J.C. Bird, A. Belmonte, et al., Nature 461, 377 (2009)].