Instability and "Pearling" States Produced in Tubular Membranes by Competition of Curvature and Tension

We investigate the stability of tubular fluid membranes by perturbing them with optical tweezers. A peristaltic instability appears, with wavelength on the order of the tube circumference, characterized by tautness and suppression of curvature fluctuations in the membrane. We interpret this in terms of a model that includes a surface tension term in the elastic energy, and describes a transition to stable, finite amplitude peristaltic states. At high amplitudes the experiment reveals new dynamic states of "pearls" interconnected via thin tubes along which they travel and aggregate.