  The desire to create cell-like models for fundamental science and
applications has spurred extensive effort towards creating giant unilamellar
vesicles (GUVs). However, a route to selectively self-assemble GUVs in bulk has
remained elusive. In bulk solution, membrane-forming molecules such as
phospholipids, single-tailed surfactants, and block copolymers typically
self-assemble into multilamellar, onion-like structures. So although
self-assembly processes can form nanoscale unilamellar vesicles, scaffolding by
droplets or surfaces is required to create GUVs. Here we show that
surprisingly, it is possible to bulk self-assemble cell-sized GUVs with almost
complete selectivity over other vesicle topologies. The seemingly paradoxical
pair of features that enables this appears to be having very dynamic molecules
at the nanoscale, that create unusually rigid membranes. The resultant
self-assembly pathway enables encapsulation of molecules and colloids, and can
also generate model primitive cells that can grow and divide.
