(728f) Thermodynamics and Kinetics of Electric Field Mediated Colloidal Crystal Assembly

The ability of nano- and micro- scale colloidal components to autonomously and reversibly assemble into ordered configurations can potentially serve as a basis to manufacture materials with exotic optical properties. However, a limited understanding of the thermodynamics and kinetics of colloidal assembly has limited the informed design of robust processes that achieve sufficiently low defect densities. To address these issues, in this work we compare measurements and models of system size dependent thermodynamic and kinetic effects in the assembly of quasi-two dimensional colloidal crystals within interfacial quadrupole electrodes. Perturbation theory and Monte Carlo simulations are used to make thermodynamic predictions of the voltages required to obtain all particles within a crystalline phase for different system sizes. These results show good agreement with video microscopy measurements of colloidal crystals containing 75-300 particles. Colloidal assembly kinetic trajectories for different systems sizes are quantified from microscopy experiments using order parameters (reaction coordinates) for local and global hexagonal ordering. These trajectories are fit with a Smoluchowski model to extract configuration dependent free energy and diffusivity landscapes. The resulting landscapes capture system size dependent non-equilibrium thermodynamics and diffusivities for different configurations as particles rearrange from fluid to polycrystalline and single crystal states. These results demonstrate the importance of system size effects to the formation and annealing of polycrystalline states in colloidal crystallization.