CAREER: Fluid Dynamics of Colloidal Crystal Film Deposition

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CBET-0747917PosnerColloidal crystal films (CCF) are being developed as photonic crystals for integrated optical circuits, as super hydrophobic surfaces, and as solid-state sieving matrices for biochemical separations. Colloidal crystal films are comprised of 20 or more layers of face center cubic packed nanospheres (20-500 nm). These films are typically deposited by a fluid self-assembly process of a non-dilute colloidal suspension of nanoscale spheres. Current CCFs are plagued with unwanted defects in the range of 20-1000 sphere diameters that limit device applications. Solvent evaporation and electrophoretic deposition methods are largely developed by trial and error and suffer from a lack of fundamental understanding of the governing physics. The ability to control colloidal crystal film structure and reduce film defects is limited by the complex role of the fluid transport on the deposition process. These flows include the coupling of free surfaces and electric fields with high volume fraction suspensions and locally varying viscosity, density, surface tension, conductivity, and permittivity. They are time-dependent, three-dimensional and exhibit a wide range of time and length scales that make them difficult to model and observe. This research investigates the transport physics of colloidal crystal film deposition where high volume fraction colloidal suspensions flow with free surfaces and electric fields. A high-speed, spinning disk confocal microscope will be developed to measure the three velocity components and crystal structure in real-time and real-space. This research will enable depositions of defect-free colloidal crystal films and structures for a host of emerging technologies. The high speed confocal system will impact a wide range of disciplines including microfluidics, rheology, colloidal science, and real-time cellular imaging. Fundamental understanding of colloidal crystallization can be applied to molecular crystallization such as protein crystallography. This program integrates research with mentoring, education and outreach impacting students from middle school through graduate school. The study includes the development of a middle school outreach program ?got flow?? for underrepresented middle school students in the Phoenix metropolitan area. The ?got flow?? program has three phases: outreach modules directly inspiring 1000 8th graders to study math, science, or engineering; RET to provide research experience and state mandated professional training for middle school teachers; and educational transfer modules (ETM) that convey the modules to individual middle schools. The PI will expand undergraduate research opportunities for Hispanic and Native Americans who have relatively high enrollment at ASU, but low representation in engineering nationwide.