Graduate Thesis Or Dissertation
 

Wireless Microwave Sensing in Environmental and Biomedical Applications

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vd66w760h

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  • This dissertation studies two different wireless microwave sensing applications in the subjects of environmental monitoring and biomedical devices. The environmental sensing application presents a design of novel wireless sensor node configurations. These nodes are intended to be used specifically in a built environment of railroad track ballast for its health monitoring. Real-time, low-cost, and long-term health monitoring in the railroad track is vital for the prevention of infrastructure failures that can cause accidents or disrupt train operations. The critical parameters of health monitoring in railroad tracks are moisture level and displacement of the railroad track components. Therefore, the experimental work was done to develop a battery-free, mechanically tunable, and narrowband wireless sensor that can be used to monitor railroad track ballast moisture level, along with an interrogator. And the moisture level information is obtained by tracking the attenuation of the signal in the propagation environment between the sensor and the interrogator. This environment comprises a heterogeneous and multi-dielectric composition of ballast, fouling material, and moisture. To approximate the actual moisture level, a dielectric mixing model is developed and presented. Additionally, a novel interferometric measurement technique that employs a pair of sensor nodes is proposed to localize the sensors and measure the displacement. The results that are in very good agreement with the analytical calculations reveal that the proposed model and technique have shown promise to accurately predict the moisture level and displacement in the real environment. The biomedical microwave sensing application is studied in the remaining part of the dissertation. An end-fire dielectric rod antenna (DRA) is proposed as a heating device for integration with an array of electroporation electrodes in order to enable efficient delivery of DNA into the cells that comprise subcutaneous tumors. A 5-7 °C temperature elevation of tumors that are located near the fat-muscle boundary and 3-7 mm below the skin surface and 7.5 mm in diameter can be achieved in a short period of time without damaging surrounding tissues. This capability is demonstrated through a combination of a directional antenna applicator operating at 8 GHz, and utilization of forced air cooling of the outer surface (skin layer). The directionality of the antenna is improved by cladding its high permittivity core with 3D printed, low permittivity dielectric material. Experimental data using a pork skin-fat-muscle tissue show that the desired temperature elevation at the tumor location is obtained after 2.5 W RF illumination for 3 minutes, which is in good agreement with electro-thermal simulations. With the addition of realistic human body model parameters to the same simulation setup, the results indicate that tumors can be uniformly heated with 3 minutes of illumination at 2.5 W input power while keeping the surrounding healthy tissues at a safe temperature. Moreover, this applicator is able to treat different sizes of tumors, up to 16 mm in diameter, by just attaching proposed thin and planar diverging lenses to the front end of a DRA. The desired 5-7 °C temperature elevation of the tumors is achieved in 3 minutes by applying 2.1-3.6 W input power depending on the size of the tumor.
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  • Pending Publication
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  • 2023-01-10 to 2024-02-11

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