(477h) Electric Field Mediated Assembly of Anisotropic Colloidal Particles

The ability to assemble anisotropic nano- and micro- colloidal particles into hierarchically ordered structures that are also potentially reconfigurable provides the basis for exotic materials and controllable devices in emerging technologies. However, current capabilities are limited by the numbers and types of non-trivial microstructures that can be reliably produced and manipulated using colloidal assembly. These limitations are due to fundamental problems with designing, controlling, and optimizing the thermodynamics and kinetics of assembly processes for complex colloidal components. Our approach to this problem is to use nonuniform AC electric fields to manipulate the position, orientation, and assembly of superellipsoidal colloids having up to three different semi-principal axes. Using inverse Monte Carlo methods, we match computer simulations to experimental observations of different concentrations and phases of superellipsoids including liquid, liquid crystal, and crystalline phases. The resulting potentials are modeled using analytical results for DLVO and novel induced dipolar contributions to particle-substrate, particle-particle, and particle-field interactions. In addition to quantifying potentials, novel order parameters have been developed to quantify microstructures and identify phases from assembled configurations, which allows such order parameters to be used as reaction coordinate to track dynamic assembly processes. Based on these fundamental models and tools, ongoing work is focused on understanding and controlling dynamic transitions between different superellipsoid configurations to manipulate non-equilibrium pathways for the assembly, disassembly, reconfiguration, and repair of hierarchically ordered anisotropic colloidal microstructures.