Assembling Colloidal Clusters From Spherical Codes

Anisotropic building blocks assembled from colloidal particles are attractive building blocks for self-assembled materials because their complex interactions can be exploited to drive self-assembly. In this work we consider the thermodynamically driven self-assembly of terminal clusters of particles[1].  This assembly process forms self-limiting anisotropic clusters with well-defined structures.  We predict that clusters related to spherical codes, a mathematical sequence of points, can be synthesized via self assembly.   Using Brownian dynamics and free energy calculations we predict the expected cluster sizes and shapes as a function of temperature and ratio of particle diameter.  Structural and dynamical analysis of these tiny systems reveal rich and sometimes surprising properties.   For example, the equilibrium structure of a 5-cluster, a square pyramid arrangement is preferred over a more symmetric structure.  Our results suggest a promising way to assemble anisotropic building blocks from constituent colloidal spheres.

[1] C.L. Phillips, E. Jankowski, M. Marval and S.C. Glotzer, “Self-assembled clusters of spheres related to spherical codes,” Phys. Rev. E, 86 (4) 1124 (2012)