Date of Graduation

8-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor/Mentor

Fritsch, Ingrid

Committee Member

Wilkins, Charles L.

Second Committee Member

Paul, David W.

Third Committee Member

Heyes, Colin D.

Fourth Committee Member

Tung, Chao-Hung Steve

Keywords

Conducting Polymer; Electrochemistry; Imaging Cytometry; Lab-on-a-Chip; Magnetohydrodynamics; Microfluidics

Abstract

In this work, a novel microfluidic pumping approach, redox-magnetohydrodynamics (R-MHD) has improved by materials and device optimization to use in lab-on-a-chip applications. In R-MHD, magnetic flux (B) and ionic current density (j) interacts to generate body force (FB) in between active electrodes, according to the equation FB = j×B. This unique fluid pumping approach is scalable, tunable, generates flat flow profile, and does not require any channels or valves. Pumping performance, such as speed scales with the ionic current density (j) and duration depends on the total charge (Q). The ionic current density (j) results from the conversion of electronic current through redox reactions of a conducting polymer like PEDOT (poly-EDOT). The enhancement of j can be obtained by the modification of polymer morphology. Therefore, electropolymerization parameters such as solvent, monomer, electrolyte, and deposition method have been optimized to improve the electrochemical performance of PEDOT. Electrodeposited PEDOT film from propylene carbonate solvent and TBAPF6 electrolyte generated a maximum of 820 µm/s flow velocity and 210 s flow duration. This enhanced system used as an imaging cytometer by coupling with a light sheet confocal microscope. This microfluidic imaging platform was able to differentiate various leukocytes cells with ~ 5000 cell/s theoretical throughput and 0.6 µm image resolution. As, our existing microscope could not analyze the R-MHD velocity profile in height direction, astigmatism particle tracking velocimetry (APTV) was employed to analyze flow profiles in three dimensions. In a microfluidic setup, flow profile is dominated by stream wise component but with no significant contributions in y and z direction. Though we achieved significant improvement in fluidic speed, flow duration was still dependent upon the total charge. Therefore, an automated magnet switching device was built which synchronized the current and magnetic field to push fluid in single direction, for unlimited time.

Additional Files
SI Video 1_Chapter 6.mov (26831 kB)
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