McPeak, Daniel2018-03-142018-03-142015-12https://hdl.handle.net/11299/194572University of Minnesota Ph.D. dissertation. December 2015. Major: Mechanical Engineering. Advisor: Ephraim Sparrow. 1 computer file (PDF); 117 pages.The research set forth in this thesis was motivated by the desire to create a microfluidic device for measuring cell concentrations in whole blood. Such a technology would enable the creation of important point-of-care diagnostic tests such as the Complete Blood Count. The path of investigation documented in this thesis was not carried out in a predetermined manner. But rather, the collected thoughts and experiments were spurred on by obstacles encountered in the pursuit of the desired technology. While the realization of a cell-enumerating device is of key interest, it was found—and is shown—that much of the challenge in creating such a device lies in addressing innate properties of the blood sample itself. As a consequence, investigation of these properties and their importance with regard to micro-scale cell transport is the primary technical focus of the research. Herein, it is shown that cell transport in creeping whole blood micro-flows is dominated by interphase flow brought about by phase-density imbalances and the elevated Darcy permeability which is associated with erythrocyte aggregation in low-shear flows. Additionally, non-uniform distribution of cells and the non-Newtonian properties of whole blood are hypothesized to affect the transport of white blood cells in situations where the rate of bulk flow changes appreciably. Study of these effects by way of experimentation and the development of mathematical descriptions of cell transport ultimately led to the creation of a device which circumvents deleterious consequences of whole blood behavior and achieves accurate quantitation of red and white blood cell concentrations.enThesis or Dissertation