Semester

Summer

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Yuxin Liu.

Abstract

Microfluidic based biotechnologies have been widely applied for biological and biomedical research and applications because the physical scales of microfluidics are suitable for biological cells and provide the ability and flexibility to control spatiotemporal biochemical parameters. The current efforts for biosensor technologies are aiming to develop detection technologies directly from small volumes of the human fluids, such as blood, urea, and saliva, for accurate, fast, and affordable detection and analysis.;Human blood provides information and supports the functioning of human body, such as nourishing tissues, regulating organs activities and defending harmful material. Blood components are the prime interests for biosensor applications in medicine research. Separation of different blood components, such as plasma, red blood cells, or white blood cells, is important for specific downstream detections (such as cancer diagnosis and biohazard detections) by preventing contamination of the plasma from blood cells' DNA. Conventional methods for blood separation include flow cytometry, centrifugation and filtration. However, high levels of skills, large volumes of samples and long processing time are usually required in these methods. Microfluidic methods for blood separation can provide advantages over these conventional methods, such as small blood volume handling, easy fabrication, fast processing, and miniaturized and portable devices for point-of-care analysis.;In this thesis work, we investigated two different microfluidic approaches for human blood separation: 1) Hydrodynamic bifurcation law based continuous blood separation. The bifurcation law, centrifugation force and Fahraeus--Lindqvist effect were employed in the approach. By using the COMSOL Multiphysics simulation, we optimized the device design, and the efficiency of blood separation of the microfluidic device was conducted using samples with different hematocrit levels and running velocities. A series of experiments were performed to investigate and quantify the two effects. The experimental results showed that the multiple bifurcation devices can provide plasma separation with high separation efficiency and yield. Electrophoresis analysis was used to examine major protein components in the separated plasma from microfluidic devices compared with that separated by a conventional centrifuge method and showed that the major proteins presented in both testing groups. 2) Membrane based passive blood separation. In this approach, a microfluidic capillary pump and a commercial Vivid(TM) plasma separation membrane were integrated to separate, collect and deliver the separated plasma from a finger-prick whole blood.;The plasma released from the membrane was collected and drawn into the microfluidic capillary pump for further downstream detection. It was demonstrated that the membrane can separate plasma depending on the natural forces of capillary action without any active pumping or electricity to operate.;Our microfluidic plasma separators are expected to be integrated with other sensing elements into a reliable, cost-effective and field-deployable biosensor for detection of heavy metals and biomarkers from a small volume of human blood. In this regard, an integration lab-on-a-chip microfluidic system needs to be further investigated, in which on-chip valves and fluid controls will be used for the system integration.

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