(458f) 3D Position and Orientation Control of Single and Assembled Colloidal Superellipsoids in Electric Fields

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 inhomogeneous AC electric fields to manipulate the position, orientation, and assembly of superellipsoidal colloids having up to three different semi-principal axes. We begin by first developing rigorous potentials to capture the position and orientation dependent DLVO particle-substrate and particle-field interactions. Microscopy results are used to validate these theoretical expressions by showing measured and modeled potential energy landscapes for up to 12 unique states for single tri-axial particles (including all combinations of position and orientation). We then show how assemblies of many particles can be used to obtain a variety of microstructures of superellipsoidal colloids, which can be controllably reconfigured between different states. Finally, we report results for the kinetics of assembly and reconfiguration, which we are using to inform the development of optimal control theories for manipulating such systems. Ultimately, with the ability to measure, model, and tune anisotropic colloidal interactions and dynamics in inhomogeneous electric fields, we demonstrate how time varying fields can be used to manipulate non-equilibrium pathways for the assembly, disassembly, reconfiguration, and repair of hierarchically ordered anisotropic colloidal microstructures.