Hg. Dobereiner et U. Seifert, GIANT VESICLES AT THE PROLATE-OBLATE TRANSITION - A MACROSCOPIC BISTABLE SYSTEM, Europhysics letters, 36(5), 1996, pp. 325-330
Giant phospholipid vesicles are shown to exhibit thermally activated t
ransitions between a prolate and an oblate shape on a time scale of se
veral seconds. From the fluctuating contour of such a vesicle we extra
ct ellipticity as an effective reaction coordinate whose temporal prob
ability distribution is bimodal. We then reconstruct the effective pot
ential from which we derive an activation energy of the order of k(B)T
in agreement with theoretical calculations. The dynamics of this tran
sition is well described within a Kramers model of overdamped diffusio
n in a bistable potential. Thus, this system can serve as a model for
macroscopic bistability.