We report the observation of phospholipid vesicles of high topology, exhibiting strong thermal fluctuations. By deeply affecting the global shape of the vesicle, these differ from the usual local thermal undulations of the membrane. They can be described as positional fluctuations of necks linking two nearby concentric membranes. Using boundary layer methods we determine the shape and elastic energy of the necks and corroborate this analysis by a numerical solution of the minimization problem. This approach leads to a qualitatively correct description of our experiments.

• Received 28 May 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.168