Pattern formation of phase-separated lipid domains in bilayer membranes

Abstract: Giant unilamellar vesicles (GUVs) composed of as few as three lipid species can phase separate into small-scale lipid domains with stripes and dots patterns. These patterns have been experimentally characterized in terms of how their size and morphology depend on temperature, membrane composition, and surface tension, which revealed inconsistencies with existing theoretical models. Here, we demonstrate that the experiments can be explained with a theory that considers both the elastic deformation of the membrane and the phase separation of lipids, which are coupled by a preferred bilayer curvature. We combine analytical and numerical approaches to elucidate how characteristic pattern size and morphology emerge from these interactions. The results agree with existing experiments and offer testable predictions such as non-monotonic dependence of the domain size on osmotic pressure and pattern hysteresis upon cycling external stimuli. These predictions motivate new directions for understanding the spatial patterning and organization mechanisms of biological membranes.