Electronic Theses and Dissertations

Identifier

643

Date

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biomedical Engineering

Committee Chair

Eugene C Eckstein

Committee Member

Michael Yen

Committee Member

Jeffrey G Marchetta

Committee Member

Thomas Hagen

Abstract

Whole blood is a complex biological fluid and its heterogeneous particulate nature distinguishes its flows from those of simple fluids. The variations in concentration, physical and biochemical characteristics of its cellular components make it one of the most challenging suspension flows to be understood and modeled for applications to blood fractionation. Current blood cell segregation studies are performed at microfluidic scale, which prohibits use of whole blood and processing of large volumes. Centrifugation based apheresis is the most common method used for collection/removal of desired/deficient blood components. It involves drawing whole blood from the donor/patient and requires specialized skills to control the centrifuge variables (spin speed, bowl diameter, idle time in centrifuge, added solutes, and plasma volume). Ultrafiltration in hollow-fiber high-flux devices such as hemofilters has been shown to provide strong separation for blood cells. For given ultrafiltration rates, the platelets exhibit elevated concentration at the walls of fibers in these devices at intermediate shear rates. In separate blood flow studies white blood cells have been shown to exist in the near wall regions of channel flows. These events are attributed to inward axial migration of red blood cells and shear induced diffusion in cross-flow filtration of particulate suspensions. Using the available knowledge of blood flow in hollow-fiber ultra-filtering devices in different regimes of flow rates we present in this dissertation an engineering effort to explore an enricher stage that operates in a continuous manner for RBC, WBC, platelets, or plasma. In this work we have developed designs and methods to fabricate and evaluate a flow-filter stage that permitted explorations of convective acceleration, shear-induced diffusion and electrokinetic manipulations of cells for whole blood and plasma fractionation. The rectangular channel geometry was used, including with a tapering zone preceding bifurcation outlets. This work demonstrates that convective acceleration in converging zones and ultrafiltration provides a means to induce small scale cell enrichment effects. We also show that ultrafiltration alone in the range of 2 – 10% of the inlet flow rates and at intermediate shear rate of ~ 670 sec-1 can enhance the cellular concentration in the outlet adjacent to the ultrafiltrative wall.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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