(362f) Fabrication of (Non-)Colloidal Crystals for Hierarchically-Ordered Materials Development

Hierarchically ordered porous materials hold promise for enhanced performance in a variety of fields. Specifically, in terms of a hierarchical pore structure (ranging from the nano-micron size regimes) many practical advantages can be derived from having a high surface area and pore volume, as well as providing size selectivity for molecule/particle diffusion and substantial interfacial area. An exceptionally promising technique for the formation of ordered porous materials is the use of colloidal crystal templating, with much attention paid to nano-scale self-assembly. Larger (micron-scale particle) components, however, offer benefits from a mass transfer as well as mechanical strength perspective and often involve easier synthesis of materials, easier yet potentially more sophisticated surface functionality, simpler measurements of the assembly process, and greater control of the interaction strength and selectivity. Despite these advantages, self-assembly at larger scales remains in its infancy. Larger components become more readily arrested in a non-equilibrium configuration (compared to nano-scale counterparts) as these larger systems are less influenced by the underlying thermal effects. This tendency for kinetic arrest limits the translation of nano-scale assembly techniques up to larger component scales. In this work, ultrasonic agitation is explored as a means of allowing large microparticles (18-750µm) to overcome kinetic barriers to packing in the creation of close-packed, highly ordered, crystalline structures. Specifically, the relationship between particle packing behavior and energy input is being characterized in terms of crystallinity. Additionally, we have extended this technique for crystal fabrication to create multi-component crystals made from two or more particle sizes. When we combine these "large-particle" assembly techniques with traditional nano-scale colloidal crystallization an exciting opportunity arises to tailor the mechanical and surface properties as well as the pore size of the resulting hierarchically structured materials.