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UBC Theses and Dissertations

Development of a microfluidic capture device for the manipulation and concentration of waterborne pathogens Jomeh, Sina


Severe epidemics in North America due to consumption of polluted water containing pathogens such as Cryptosporidium parvum and Giardia led to the development of standard detection methods like USEPA 1623 (by US Environmental Protection Agency). USEPA 1623 method, although fairly practical, is still at its infancy. There are still questions and ambiguity about the precision and accuracy of this method for the separation and detection of pathogens. USEPA 1623 includes a series of lengthy unreliable procedures that are highly prone to failure. The main purpose of this study is to examine the feasibility of developing alternative methods to improve pathogen recovery. The proposed method includes a microfluidic flow cell which implements physical properties of the pathogens (e.g., mass and electric charge) to manipulate, separate and concentrate them for future detection step. In general, the proposed device includes a flow path with an arbitrary shape through which water sample is flushed. The device then separates and concentrates the pathogens at the proximity of the “capture sites” where they are trapped by complementary antibody molecules. In order to design such a device, first, continuum numerical simulation is used to determine the optimum device geometry from among the many possible configurations. In addition to the device geometry, the effect of two mechanisms, sedimentation and electrophoresis, related to the physical properties of the pathogen is numerically studied using continuum simulation to enhance the pathogen separation process. Discrete numerical simulation is implemented afterwards to achieve a clear understanding of physical phenomena occurring at the molecular level close to the capture sites. The results obtained from the numerical modeling are used to fabricate a microfluidic test cell. The test cell is then examined in terms of pathogen separation and capture performance, and the experimental results are compared with those obtained by the modeling. It is shown that the proposed capture method has a better recovery with a higher precision when used along with the sedimentation process. Electrophoresis, however, introduces new challenges to the problem which necessitates further investigation of the method. Some of the most important challenges are discussed, and the potential remedies are suggested.

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