“Computational investigation of multipolar colloidal particles”
Colloids with anisotropic charge distributions hold promise for creating a number of useful new materials including optic materials with novel symmetries, materials for information storage, and dampers for controlling vibrations in structures. Experimentally manipulating properties of anisotropic particles in a controlled fashion can sometimes be difficult and is time consuming. The search for novel anisotropic colloidal materials can be enhanced and even guided by simulations of colloidal system assembly. We report the results of three projects. In the first we use discontinuous molecular dynamics simulation to investigate how the internal charge separation on anisotropic, dipolar colloidal rods with 4:1 aspect ratio affects their phase behavior with particular focus on formation of networked structures. In the second project, we perform Brownian Dynamics simulations of simple superparamagnetic microspheres subjected to application of uniform magnetic and AC electric fields. The interconnected bidirectional structures that form are in excellent agreement with experiments in the Velev Laboratory. In the third project we consider the case in which the “charge” – “charge” separation on particles in crossed magnetic and electric fields is allowed to vary continuously from dipole-like to patchy-like with four patches. As this distance increases at low temperatures, we observe a transition from regular to slippery diffusion-limited cluster aggregation, and dramatic changes in the aggregates’ underlying lattice structure from square-like to hexagonal ordering. The insights gained from these studies help our experimental colleagues to screen the many types of structures formed by anisotropic particles so as to identify those that would be of interest for advanced applications.