  Elastic crystalline membranes exhibit a buckling transition from sphere to
polyhedron. However, their morphologies are restricted to convex polyhedra and
are difficult to externally control. Here, we study morphological changes of
closed crystalline membrane of super-paramagnetic particles. The competition of
magnetic dipole-dipole interactions with the elasticity of this magnetoelastic
membrane leads to concave morphologies. Interestingly, as the magnetic field
strength increases, the symmetry of the buckled membrane decreases from 5-fold
to 3-fold, to 2-fold and, finally, to 1-fold rotational symmetry. This gives
the ability to switch the membrane morphology between convex and concave shapes
with specific symmetry and provides promising applications for membrane shape
control in the design of actuatable micro-containers for targeted delivery
systems.
