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UBC Theses and Dissertations

Development of radio frequency/microwave platforms for liquid sensing in environmental and medical applications Mohammadi Gharalar, Sevda

Abstract

Real-time monitoring of liquids and their contents has paramount importance in numerous fields, including point-of-care medical diagnosis, pharmaceutics, water quality assessment, monitoring ethanol in fermentation broths and electrolytes in human sweat and other environmental/biomedical industries. The essence of this thesis is to employ the dielectric properties of materials in pursuit of realizing real-time miniaturized devices to perform sensing with low consumption of samples, micro/nanoliters. This was achieved through design, implementation, and experimental validation of several proposed sensing platforms including passive and active microwave resonator sensors as well as integrated sensors on complementary metal-oxide semiconductor (CMOS) process for lossy liquids detection. For passive sensor structure, the development of channel-integrated microwave sensors operating in reflection and transmission mode were investigated. A non-contact transmission-based resonator was developed to monitor the organics (glucose, acetate and glucose-acetate mixture) and the chemical oxygen demand (COD) standard in concentrations ranging from 50 to 800 mg/L. The reflection-based coplanar waveguide resonator was implemented for aqueous dielectric detection, where the concentrations of glucose and salt in the range of 50-1200 mg/dL were detected in volume of 0.784 µL solutions. In active sensing method, a substrate-embedded channel in split-ring resonator-based sensor was developed to enhance the sensitivity in liquid and solute detection by up the 60 %. An active feedback loop was added to boost the quality factor by over 100 times compared to passive counterpart. The developed sensor detected detect the low concentrations of ethanol (0-0.08 vol%) and salt (0-200 mM) in water using an effective volume of 7.85 µL and 4.56 µL, respectively. Finally, a silicon-based CMOS technology was adopted to realize a compact fully integrated liquid sensor, featuring detection in MHz range of frequency while offering a small footprint. This sensing platform also aimed to eliminate analog to digital interface, increase the robustness of the sensor to low frequency noises and also reduce the required sample volume down to nanoliter.

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Attribution-NonCommercial-NoDerivatives 4.0 International