  Highly symmetric nano-shells are found in many biological systems, such as
clathrin cages and viral shells. Several studies have shown that symmetric
shells appear in nature as a result of the free energy minimization of a
generic interaction between their constituent subunits. We examine the physical
basis for the formation of symmetric shells, and using a minimal model we
demonstrate that these structures can readily grow from identical subunits
under non equilibrium conditions. Our model of nano-shell assembly shows that
the spontaneous curvature regulates the size of the shell while the mechanical
properties of the subunit determines the symmetry of the assembled structure.
Understanding the minimum requirements for the formation of closed nano-shells
is a necessary step towards engineering of nano-containers, which will have far
reaching impact in both material science and medicine.
