Equilibrium electrodeformation of a vesicle in an ac electric field

Under an ac electric field the equilibrium shape of a vesicle (closed liposome) depends on various physical parameters, such as the electric field frequency, mismatch in fluid conductivities and permittivities. In this work we use a spheroidal model to investigate these dependences. We derive the transmembrane potential for a leaky dielectric spheroidal shell and compute the equilibrium spheroidal shape. When compared with experiments and previous small-deformation analysis, we found that the spheroidal model agrees better with the experiments. In particular the spheroidal model allows for asymptotic analysis on the cross-over frequency between prolate and oblate vesicles, and the comparison with experiments near the cross-over shows that the spheroidal model captures the prolate-oblate transition better than the small-deformation theory.