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defense cindy hanson

The Use of Microfluidics and Dielectrophoresis for Separation, Concentration, and Identification of Bacteria

Monday, August 7
1:00 PM • ENGR 406

Cynthia Hanson
Doctoral Candidate Dissertation Defense
Department of Biological Engineering

Advisor - Elizabeth Vargis, 435-797-0618


Traditional bacterial analyses take one to two days under favorable conditions where the bulk of the time is spent waiting for bacteria to divide and grow till visual colonies can be observed for identification. In the case of bacteria with slow doubling times, this process can take weeks. This delay in analysis is unacceptable especially in the case of life threatening diseases or emergencies. It is clear that in order to decrease the analysis of the bacteria, the culturing and growth step must be circumvented. The goal of this research is to design, build, and test a device that could decrease the analysis time of bacteria using label-free methods of dielectrophoresis and Raman spectroscopy.

Testing for device design was performed with clinical samples in mind, which consist of bacteria grown in a variety of environmental conditions (available food sources, growth stage, temperature, etc.) and accompanied by sample debris. Raman spectra of bacteria grown in varying media and metabolic stages were collected and analyzed. Results indicate that growth phase and media have in impact on Raman spectra and is distinguishable by linear discriminant analysis (LDA). Despite these spectral differences, it was found that LDA classification of closely related bacteria remains fairly high regardless of growth phase. As such, the use of Raman spectroscopy as a means of identification played an important factor in device design. Sample debris was also considered in device design and accommodated for by dielectrophoresis. Devices were built with the goal to isolate bacteria from a mixed sample and simultaneously acquire Raman spectra for identification. 

In this dissertation, a device was designed, built, and tested that incorporates dielectrophoresis for particle isolation and Raman spectroscopy for identification. Trapping and identification of polystyrene microspheres was used to demonstrate proof of concept and COMSOL simulations was used to determine theoretical feasibility for trapping bacteria in the same device. Results indicate a clear potential for the cDEP-Raman device to isolate and identify bacteria from sample debris, and thereby decrease the analysis time of bacteria.