The influence of ac electric field on the shape and thermal fluctuations of giant vesicles is theoretically investigated. The experiments show that at high frequencies (dielectric regime) vesicles deform into oblate ellipsoids with the symmetry axis parallel to the applied electric field, while at low frequencies (conductive regime) they deform into prolate ones. Depending on the medium conductivity, the transition frequency between both regimes may be as low as a few kilohertz.

• Received 21 December 1992

DOI:https://doi.org/10.1103/PhysRevE.48.628