Doctor of Philosophy (PhD)


The School of Electrical Engineering and Computer Science

Document Type



Quartz crystal microbalance (QCM) has been widely studied as a mass sensing technique in laboratory environments and has shown a wide range of industrial applications such as food quality control, various forms of chemical detection, and biomolecular recognition under gas phase as well as liquid phase media. The construction of multi-sensor arrays combined with special sensor coatings enables multiple analyte detections and discrimination of multi-analyte along with statistical analysis. Despite the great sensing capabilities of QCM and growing interest in practical applications beyond the laboratory setup, most QCM studies are still performed in laboratory settings with benchtop QCM instruments. Therefore, the development of a portable QCM system achieving comparable performance to benchtop instruments is desired for field-deployable applications and in situ detection.

QCM experimental setup typically consists of two independent systems: a measurement system and a fluidic system. As a first step to developing a fully portable QCM instrument, a miniaturized single-channel QCM measurement circuit system was proposed. The developed system is a fully customizable, miniaturized, battery-powered, and effective QCM system utilizing a phase-locked loop (PLL) circuit. The proposed system does not rely on the quality of a clock signal, which is critical in typical frequency counters to improve measurement performances such as measurement time and frequency resolution. In addition, a two-channel gas flow control system was developed, which independently controls the flows of the carrier gas and the analyte gas. A fully portable QCM system was fabricated by combining a single-channel QCM measurement system with a custom-designed fluidic system that included the flow control system.

Finally, the fully portable QCM system was improved by implementing a four-channel measurement capability. The developed system can measure up to four sensors simultaneously with a four-channel flowcell and measurement system, which allows it to be used for the detection, discrimination, and statistical analysis of multiple analytes.



Committee Chair

Park, Kidong