Madelyn Thomae Mechanical Engineering MS Thesis Defense

MEMS Resistance Temperature Devices Designed and Characterized for Subzero and Arctic Applications

Research has shown that microorganisms play a major role in climate change, but there is a lack of adequate understanding of the microbial involvement in climate change and needs to be further researched. Temperature monitoring gives an insight into the current climatic shifts in Arctic and Antarctic regions. Currently, satellite monitoring is used to track temperature changes in those regions. To further the understanding of the mechanisms that microorganisms play in the rising temperatures in those regions, in-situ temperature monitoring is needed. Commercially available temperature probes are high cost and not well-suited for the harsh environment of Arctic and Antarctic regions. Utilizing micro electromechanical systems technology provides a solution for robust low-cost, low-power sensors that can be designed to operate in harsh environments.

Gold resistance temperature devices were designed and fabricated using micro electromechanical systems technology that had a high spatial resolution capable of detecting microorganisms in subzero applications. The fabricated temperature sensors were calibrated for subzero use and freezing experiments were done to detect any changes due to impurities in the sample. The gold resistance temperature devices were able to withstand prolonged exposure to the harsh experimental environment and provide an accurate spatial temperature gradient throughout the media. The gold resistance temperature devices had negligible effects due to the self-heating phenomenon common in resistance temperature devices. Additionally, the sensors were able to detect variations in the freezing curve of the media with the inclusion of the bacterial isolate Flavobacterium sp. ANT 11 (accession number GU592435; Dieser et. al) in DI water samples. Future research should focus on (1) furthering the understanding of the microbial interactions in the cooling curves of different medias and (2) integrating electrical impedance spectroscopy sensors to provide knowledge of what impurities are in the sample that could be affecting the freezing curve of the media.

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