Self-assembly of reconfigurable colloidal molecules

The lock-and-key colloidal particles of Sacanna et al. are novel "dynamic" building blocks consisting of a central spherical colloidal particle (key) attached to a finite number of dimpled colloidal particles (locks) via depletion interactions strong enough to bind the particles together but weak enough that the locks are free to rotate around the key. This rotation imbues a mechanical reconfigurability to these colloidal "molecules". Here we use molecular simulation to predict that these lock-and-key building blocks can self-assemble into a wide array of complex crystalline structures that are tunable via a set of reconfigurability dimensions: the number of locks per building block, bond length, size ratio, confinement, and lock mobility. We demonstrate that, with reconfigurability, ordered structures - such as random triangle square tilings - assemble, despite being kinetically inaccessible with non-reconfigurable but similar building blocks.