Small voltage electrocapillary flows in the presence of ionic surfactants

Rapid flows were observed by applying a small voltage across an organic-aqueous interface in the presence of an ionic surfactant. These flows are in contrast to the experiments of G. I. Taylor and J. R. Melcher [Annu. Rev. Fluid Mech. 1, 111 (1969); D. A. Saville, Annu. Rev. Fluid Mech. 29, 27 (1997)], where no ionic surfactant was used. In their experiments, a large voltage difference was necessary to induce a surface charge between two leaky dielectric fluids. Here, we intentionally create a surface charge by adding a cationic surfactant. The result is that a much lower voltage is necessary to cause substantial flows. Two experiments are performed to compare these results with classical thermocapillary flow experiments. (C) 2002 American Institute of Physics.