Surfactant transfer through a liquid membrane: origin of spontaneous oscillations at the membrane/acceptor phase interface.

Instability due to surfactant redistribution in a liquid membrane system consisting of two solutions, namely source and acceptor, separated by a layer of immiscible liquid is studied theoretically and experimentally. The transfer of a surfactant from a source phase to an acceptor phase is often accompanied by spontaneous nonlinear oscillations of electrical potential and/or interfacial tension. The oscillations can be generated at each of the membrane interfaces. Here a mechanism of oscillation, which develops at the membrane/acceptor phase interface, is proposed on the basis of direct numerical simulation of the system evolution. Performed experimental studies confirm the theoretical results.