CAREER: Nuclear Magnetic Resonance Microscopy Studies of Microfluidic and Porous Media Transport

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AbstractCTS-0348076J. Seymour, Montana State UniversityThe modeling of colloidal suspension transport in small channels is relevant to mixing in microfluidic devices for sensor technology, to the sorption of microbial bacteria in medical implant infections and earth formation bioremediation and to filtration devices and other porous media used for separations. Improved models of such systems could have a broad impact to society through design of medical sensors and filtration devices and environmental bioremediation strategies. The hypothesis of the research is that the nonequilibrium microstructure and dynamics of colloid suspension flows in micro-channels, capillary networks and porous media can be characterized using NMR microscopy. Dynamics of colloidal particles in channels of the order of 100 micrometers are relevant to microfluidic applications such as biosensors and 'lab on a chip' systems and are the basis of colloid transport in the network of pore spaces in porous media. NMR microscopy methods allow noninvasive measurement of time and length scale dependent displacements within opaque systems such as colloidal suspensions and provide unique data for testing of conceptual and numerical models. The research will begin with rectilinear flows of model spherical colloidal particles in a Couette geometry and progress to single capillaries, capillary bifurcations, capillary networks and porous media. Cellular suspensions of blood and microbial bacteria will be studied in these same flow systems to test the relevance of hard sphere colloid models to transport of natural systems.The objectives of the research are:1) To test computer models of colloid rheology by measurement of the microstructure, velocity distribution and diffusion tensor of model and cellular suspensions in Couette flows using NMR microscopy methods2) To measure the concentration distribution, velocity and hydrodynamic dispersion tensor of model and cellular colloid suspension flows in straight capillary microchannels, capillary microchannel bifurcations and networks in order to model mixing processes relevant to microfluidic and physiological flows and incorporate rheological data from objective 1) into such models3) To provide the first non-invasive measurements of concentration distribution, velocity and hydrodynamic dispersion in model and cellular colloidal suspension flows through porous media in order to incorporate microhydrodynamics into models for colloid deposition and transport in porous media4) To integrate multiphase transport in microfluidic devices and porous media into the undergraduate and graduate curricula using NMR microscopy flow visualization.These objectives will provide quantification of the microscale hydrodynamics influencing colloidrheology, mixing in microfluidic flows and colloid transport and deposition in porous media. The significance of this work lies in the potential for new insight into existing theory and experiments by providing data on opaque colloidal dispersion dynamics not available by other techniques.The prevalence of colloid transport issues in industrial, biomedical and environmental applications and the computer and digitizer upgrades of the campus NMR facility DRX250 that will benefit all users, gives the project broader impacts to society.The exploration of the lower resolution limits of NMR microscopy for measurement ofnonequilibrium transport coefficients in microfluidic transport, where these methods have yet to be applied, will provide a key link between prior data on macroscopic system behavior andmicroscale dynamics, lending insight into issues of scale down engineering in microfluidics. The flow visualization aspects of NMR microscopy will be used to integrate concepts from colloidrheology with mixing in microfluidics and deposition in porous media into the undergraduate curricula, providing a connection between core concepts in transport phenomena like Taylor-Aris dispersion and advanced concepts such as non deterministic chaotic mixing.