(484a) Dual Nature of the Packing and Assembly Behavior of Multi-Dimpled Spheroidal Particles

Single dimpled concave spheroidal particles ranging from bowls to lenses serve as a toy model of lock-and-key interactions. Spheroidal particles can be extended to those made of unions and intersections of many spheres and the volume outside spheres to produce multi-dimpled spheroids. Using Monte Carlo simulation of recently synthesized concave spheroidal particles with two, three, four and six symmetric dimples, we investigate the geometric and thermodynamic conditions under which the spheroids behave like spheres. We show that the particles exhibit a dual nature in their packing and assembly behavior where they sometimes behave as spheres and sometimes do not, and we show that this duality results from a competition between the convex and concave features of the particles upon crowding. This dual nature is controlled by global vs. local features, with universal features common to all symmetrically dimpled spheroids. We argue that shrinking and swelling the size of such particles can be used to experimentally realize this dual behavior, providing a route towards reconfigurable structures.