Immiscible lipids control the morphology of patchy emulsions

We study the phase behavior of immiscible mixtures of phospholipids and cholesterol at the interface of oil-in-water emulsions, which governs the surface morphology of patchy droplets. Emulsification with lipid mixtures leads to domain formation with a variety of shapes, such as spots, disordered stripes, hemispheres and rings. We map out the ternary immiscibility diagram of our system, which allows one to control the geometry of patches on the droplet surface. By contrast to short-lived domains on liposomes, image analysis of the individual domains shows that emulsion spots grow towards a steady state size distribution and remain stable over weeks. These domains are functionalized with biotinylated lipids, which makes them useful candidates for directed self-assembly through specific interactions via streptavidin. Here we bind streptavidin coated beads to these lipids and find that the binder diffusion constant depends on the morphology of the droplet. These fluid patchy particles offer a versatile system in which the geometry and the dynamics of the sticky patches are under control.