  Using a microfluidic trap, we study the behavior of individual phospholipid
vesicles in contact with fatty acids. We show that spontaneous fatty acids
insertion inside the bilayer is controlled by the vesicle size, osmotic
pressure difference across the membrane and fatty acids concentration in the
external bath. Depending on these parameters, vesicles can grow spherically or
become unstable and fragment into several daughter vesicles. We establish the
phase diagram for vesicle growth and we derive a simple thermodynamic model
that reproduces the time evolution of the vesicle volume. Finally, we show that
stable growth can be achieved on an artificial cell expressing a simple set of
bacterial cytoskeletal proteins, paving the way toward artificial cell
reproduction.
