(233c) Convective Assembly of Nanostructured Materials

Convective deposition of nano- and microscale particles is used as a platform for scalable nanomanufacturing of surface morphologies to control and enhance photon, electron, and mass transport. The fundamental mechanism behind self-organization of these particles is attraction driven by the local capillary interactions and flow steering of particles confined in a thin film of an advancing meniscus. By studying and altering thin film dynamics, we can control morphology and various instabilities that occur during deposition of mono- and bidisperse suspensions. For instance, by adjusting the suspension profile we alter assembly from a particle-by-particle deposition to a pre-organized deposition mode that affects the deposited morphology. Likewise, lateral mechanical oscillatory motion of the substrate alters the mode of deposition increasing the rate of deposition and reducing the sensitivity of the process to fabricate crystalline monolayers and the unique ability to form flow-templated long range thin film FCC 100 colloidal crystals. This process has been successful in fabricating coatings that enable or enhance performance of light emitting diodes (LEDs and OLEDs), dye sensitized solar cells (DSSCs), polymeric and inorganic membranes, and cell capture platforms. This process has been scaled up to fabricate roll-to-roll colloidal monolayers by decoupling the evaporation from the colloidal assembly. Our latest investigations of Janus particle fabrication and polymer diffusivity in nanoconfinement will be highlighted. Support for this work has come from the National Science Foundation CBET and the Scalable Nanomanufacturing Program, the Department of Energy, the PA NanoMaterials Commercialization Center, and the Johns Hopkins University Applied Physics Laboratories.