Shape Instabilities in the Dynamics of a Two-Component Fluid Membrane

We study the shape dynamics of a two-component fluid membrane, using a dynamical triangulation Monte Carlo simulation and a Langevin description. Phase separation induces morphology changes depending on the lateral mobility of the lipids. When the mobility is large, the familiar labyrinthine spinodal pattern is linearly unstable to undulation fluctuations and breaks up into buds, which move towards each other and merge. For low mobilities, the membrane responds elastically at short times, preferring to buckle locally, resulting in a crinkled surface.