(351c) Integrated Self & Directed Assembly of Interfacial Colloidal Crystals Via Electric Field and Depletion Mediated Attraction

The autonomous and reversible assembly of nano- and micro- scale components is an essential process in numerous emerging technologies. As a result, there is great interest in understanding how thermal motion, particle and surface interactions, and external fields can be optimally coupled in assembly processes to elicit desired material and device responses. We approach this problem by directly and quantitatively connecting colloidal interactions, dynamics, and microstructures using optical microscopy (i.e. evanescent wave, video, confocal) and simulation (i.e. Monte Carlo, Stokesian Dynamics) methods. Here we investigate how depletion attraction mediated self-assembly and electric field mediated directed-assembly can be integrated to assemble defect-free colloidal crystals and avoid undesirable states (e.g. amorphous, polycrystalline, or arrested configurations). General strategies investigated include: (1) initiating depletion mediated self-assembly processes and then applying electric field mediated directed-assembly to overcome kinetic bottlenecks, (2) using electric-field directed-assembly to generate non-equilibrium configurations as transition states before initiating depletion mediated self-assembly, and (3) simultaneously using depletion and electric field mediated colloidal crystal assembly. Our findings indicate how integration of self- and directed- assembly can lead to thermodynamically stable equilibrium colloidal crystals via non-equilibrium kinetic pathways.