Topology-driven surface patterning of liquid spheres

Surfaces of classical spherical liquid droplets are isotropic, promoting the random distribution of surface-adsorbed molecules¹. Here we demonstrate a counterintuitive temperature-controlled self-assembly of well-defined and highly ordered patterns of surface-adsorbed fluorescent molecules on the surfaces of water-suspended spherical oil droplets. These patterns are induced by precisely self-positioned, topology-dictated structural defects in a crystalline monolayer covering these droplets’ surfaces over a wide temperature range. We elucidate the pattern formation mechanism, visualize the defects’ positions and map the stress fields within the surface crystal. The observed phenomena provide insights into the interfacial freezing effect on curved surfaces, enable precise positioning of functional ligands on droplets for their self-assembly into higher-hierarchy structures^2–6 and may also play an important role in vital protein positioning on cell membranes⁷ and morphogenesis^8–12.