Geometrical Pinning and Anti-Mixing in Scaffolded Lipid Vesicles*

Cellular membranes are highly compartmentalized structures comprised of specialized lipid domains. Unraveling the physical mechanisms behind the organization lipid domains is a central goal in membranes biophysics, while the ability of reproducing them in synthetic structures holds great potential for applications in self-assembly, bio-sensing and drug delivery. Previous studies on multi-component vesicles and supported lipid bilayers have unveiled a fundamental interplay between the membrane geometry and lipid composition. However, the detailed mechanisms behind this coupling and their role in the organization of lipid domains remain incompletely understood, because of the impossibility of independently controlling the membrane geometry and composition. Here we overcome this limitation by fabricating multicomponent lipid bilayers supported by colloidal scaffolds of prescribed shape. Thanks to a combination of experiments and theoretical modeling, we demonstrate that the substrate local curvature and the global chemical composition of the bilayer determine both the amount of mixing and spatial arrangement of the lipid domains.