(423g) Stress-Driven Colloidal Crystal Reassembly through Darcy Flow during Vibration Assisted Convective Deposition

The realization of structural diversity in colloidal crystals obtained by self-assembly techniques remains constrained by thermodynamic considerations and current limits on our ability to alter structure over large scales using imposed fields and confinement. Following previous work, a convective-based procedure to fabricate multi-layer colloidal crystal films with extensive square-like symmetry is enabled by periodic substrate motion imposed during the continuous assembly. The generation of extensive single crystalline (100) fcc domains as large as 15 mm² and covering nearly 40% of the colloidal crystalline film is possible by simply tuning coating conditions and multi-layer film thickness. Preferential orientation of the square-packed domains with respect to the direction of deposition is attributed to domain generation based upon a shear-related mechanism. We propose the orientation of these crystals is a result of the stress caused by Darcy flow through the crystal. Crystal orientation changes the relative resistance, causing domains to preferentially anneal into structures with prefered orientation. Further evidence is the periodic defects found in the (100) upward-facing domains that cannot be fabricated by particle-wise assembly.