Anisotropic micro and nanoscale building blocks provide new opportunities for significantly extending the scope of colloidal self-assembly, and enabling the formation of interesting crystalline superstructures that are otherwise inaccessible. Due to the complexity of these building blocks, however, it is not evident what type of superstructures can be targeted from different types of building blocks. The high-dimensional parameter space that defines the geometric and interaction properties of such systems poses an obstacle to assembly design and optimization. Specifically, a system with multiple types of anisotropic building blocks can self-assemble into complex structures that are hard to predict, but at the same time, could possess interesting transport properties such as tunable phononic or photonic bandgaps.
Here, we present a theoretical and computational study of the interactions and self-assembly behavior of superstructures of colloidal clusters. These units are experimentally synthesized from a number of spherical particles that are permanently bonded together and form various cluster shapes such as cubes or tetrahedra. We use molecular dynamics (MD) and Brownian dynamics (BD) simulations to investigate the interactions of colloidal clusters with different shapes through their complex surfaces and interfaces. Geometric constraints are also investigated to help determine particle sizes and configurations that can result in the design of ordered superstructures. Finally, MD and BD simulations are used to predict thermodynamics and kinetics of self-assembly for a variety of binary and ternary configurations. This theoretical/computational study provides a direct insight into various parameters that affect the interactions between colloidal clusters, and leads to a dimensionality reduction and definition of practical design guidelines for future experimental efforts to synthesize high quality superstructures with long-range order.