Abstract :
An interface between two immiscible, nonionic fluids becomes unstable if an electric field is applied and if the angle between the field and the interface normal is smaller than a critical angle. We do not assume the presence of ions on the interface in contrast to previous work. The characteristic wave number k* of the undulations is proportional to the square of the field and inversely proportional to the surface tension. We also show that a thin layer on a capacitor plate loses its stability more easily than an interface far from the plates. New effects can be expected in near-critical fluids, in which the surface tension is small and k* can be much larger than the inverse of the capillary length. Moreover, k* ultimately exceeds the inverse of the correlation length very close to the critical point, where the critical behavior and the domain structure are drastically altered by electric field.
