Solid Domains on Giant Lipid Vesicles: Growth of 2D Crystals on Curved Surfaces

The growth of two-dimensional crystals on surfaces has aroused much attention in recent decades. Theory predicts, and early experiments on 2D colloidal assembly are starting to show, how evolving crystal patterns on surfaces of non-zero Gaussian curvature produce complex patterns. In this study, we investigate how solid lipid domains grow in the nanometrically-thin bilayer membranes of giant unilamellar vesicles and how the growth pattern results from the interplay of membrane tension and curvature. This system is interesting and sophisticated because it differs from colloidal system in the following aspects including the smaller molecular rather than colloidal dimensions of building blocks and tension at the edge of the solid domains. Here, we focus on how solid domains assume a flower-like shape as they grow on giant vesicles. We find that solid domains appear hexagonal when grown under low tension but grows into 6-petal flowers after reaching critical size under high tension, with the petals bending to envelop the vesicle. By varying the membrane tension and curvature, flowers with different petal length and secondary features can be observed.