Vesicle deformation in DC electric pulses.

The transient deformation of giant vesicles in square DC electric pulses is investigated. We experimentally observe the theoretically predicted transition from an oblate to prolate ellipsoidal shape in the case of a quasi-spherical vesicle encapsulating solution less conducting than the suspending medium. The transition is detected by utilizing a two-step pulse in order to avoid electroporation and vesicle collapse. We develop a theoretical model to describe both the deformation under an electric field and relaxation after the field is turned off. Agreement between experiment and theory demonstrates that the time-dependent vesicle shape can be used to measure membrane properties such as viscosity and capacitance.