Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Dr. Jun Yang

Abstract

Medical diagnostics plays a critical role in human healthcare. Blood analysis is one of the most common clinical diagnostic assays. Biomedical engineers have been developing portable and inexpensive diagnostic tools that enable fast and accurate tests for individuals who have limited resources in places that require such field applications. The emergence of Lab-on-a-CD technology provides a compact centrifugal platform for high throughput blood analysis in point-of-care (POC) diagnostics. The objective of this thesis work is to develop a Lab-on-a-CD system for parallel quantitative detection of blood contents.

Blood separation is a key step in blood analysis. By integrating out-of-plane microvalves into the Lab-on-a-CD system, pure plasma is separated from human whole blood sample for subsequent blood detection. These out-of-plane microvalves show excellent performance in preventing backflow or reverse mixing due to blood cell diffusion. The concentrations of certain blood contents in the separated plasma can be detected using the electrochemical biosensors embedded in the plasma reservoir. To improve sensitivity, a nanoporous structure is created on the surfaces of the biosensors’ electrodes through an alloying/dealloying process. The nanoporous electrode has an electroactive surface area up to 60 times larger than that of a flat gold electrode of the same size. As a result, numerous catalysts and enzymes are stably entrapped in the nanoporous structure, leading to high sensitivity, stability and reproducibility of the biosensor.

Based on this devised blood separation technique and the improved electrochemical detection method, a Lab-on-a-CD prototype was constructed and successfully applied in the concentration detection of glucose, lactate and uric acid with linear ranges of 0 – 30 mM, 0 – 1.5 mM and 0 – 5 mM, respectively. Furthermore, the volume of whole blood sample consumed for each section can be as small as 16 µL.

The Lab-on-a-CD platform developed in this thesis is low-cost, robust, and simple-to-use. Potentially, it could be used in clinical diagnostics and will especially aid developing countries where resources are limited.

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