Figure 1. Layer-by-layer assembly schematic.

a, Capture cups each retain a single droplet that contains aqueous cytoplasmic material (AQ_cy, blue) in a mixture of oil-lipid 1 (yellow). A monolayer of lipid 1 stabilizes the droplets. b, Oil-lipid 2 (green) mixture replaces oil-lipid 1. c, Extracellular aqueous phase (AQ_ex, blue) replaces oil-lipid 2. As the AQ_ex/oil interface traverses the array, it envelopes each trapped droplet and lipids in the interfacial monolayer composed of oil-lipid 2 deposit on the trapped droplets. d, Complete exterior phase exchange transforms the droplets into unilamellar vesicles. e, Exchanging AQ_ex with oil-lipid 3 deposits a third lipid leaflet onto the unilamellar vesicle to produce a triple monolayer droplet. f–g, Introducing oil-lipid 4 followed by AQ_ex deposits a final fourth leaflet of lipids. h, The final product after three phase exchanges is a double bilayer vesicle.