[CCoE Notice] ChBE Seminar: Collide and Conquer: Flow-Induced Segregation Phenomena in Blood and Other Multicomponent Suspensions

[Grayson, Audrey A]

ChBE Dept. Seminar
10:30am-11:30am, Friday, March 21, 2014
Rm W122
Collide and Conquer: Flow-Induced Segregation Phenomena in Blood and Other Multicomponent Suspensions
Michael D Graham
University of Wisconsin-Madison
ABSTRACT:

Blood is a suspension of particles of various shapes, sizes and mechanical properties and the distribution of these particles during blood flow is important in many contexts. Red blood cells (RBCs) tend to migrate toward the center of a blood vessel, leaving a so-called cell-free layer at the vessel wall, while white blood cells (WBCs) and platelets are preferentially found near the walls, a phenomenon called margination that is critical for the physiological responses of inflammation and hemostasis. Potential beneficial effects on hemodynamics arise from addition of high molecular weight long-chain polymer molecules known as drag-reducing additives (DRAs) to blood; one effect of these additives is the reduction of the cell-free-layer thickness. Additionally, the segregation properties of WBCs, platelets, and RBCs can be employed for their separation or detection in microfluidic devices. Finally, drug delivery particles in the bloodstream will also undergo segregation phenomena - the influence of these phenomena on the efficacy of such particles is unknown.

This talk describes efforts to gain a systematic understanding of flow-induced segregation phenomena in blood and other complex mixtures, using a combination of theory and direct simulations of flowing suspensions. Two specific issues are addressed here: (1) the effect of DRAs on the formation of the cell-free layer and (2) the origin of the margination phenomenon and its dependence on the relative properties of the different types of suspended particles in a mixture. In the case of polymer additives, the experimentally observed thinning of the cell-free layer is reproduced in the simulations and the mechanism underlying it is described.  The study of margination reveals that this phenomenon is strongly affected by the nature of pair collisions between different types of particles during flow. Having in hand an understanding of the mechanisms underlying these phenomena now allows more rational approaches to development of quantitative models of them and processes that exploit them. This knowledge will also lead to a better understanding of the consequences of these phenomena in physiology and medicine.






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