Shape transformations in single-layer carbon nanotubes

We show that strong electron irradiation of single-layer carbon nanotubes introduces distinct changes in the preferred morphology (shape) of tubes, from perfect cylindrical to a necklace of ridges which result from local deformations of the tube surfaces with the curvature on the order of the tube radii. The shape transformations in these free-standing closed two dimensional surfaces seems to resemble closely the deformations observed in systems such as lipid bilayers and biological membranes.