FIG. 1.

(a) Bilayers are formed at the interfaces of lipid coated water-in-oil droplets. By bringing together more than two droplets, networks of sequential bilayers can be generated. (b) When a squeezed droplet partially enters a “rail” (a groove on the channel surface) its surface energy is reduced. This creates an energy gradient at the edge of the rail, which leads to an attractive force pulling it towards the deeper areas. This lower energy state causes the droplet to continue travelling along the direction of the rail, meaning the direction of travel can be defined in 2D space.