The objective of this research is to investigate miniature radiometric sensors that conform to a surface under test and are capable of thermal imaging to varying depths via frequency adjustment. The approach is based on the use of flexible microwave antennas within which integrated circuits are embedded to detect thermal radiation in the microwave frequency range, and dynamically adjust the sensor characteristics to account for variations in the properties of the contacting surface, such as human skin. The sensors can be applied for mobile monitoring of internal body temperature, wound healing, and other physiological phenomena.
The intellectual merit of this project lies in advancements in antenna design, nanoscale ferroelectric devices and radiometer design, enabling a transformative change in passive microwave sensing. Specific advances targeted in this research include: conformable and frequency-agile antennas; impedance-sensing integrated circuits with embedded tuning networks; and a chip-scale radiometer that can be directly integrated into the antenna.
The broader impacts of the project include advancements in the general field of microwave sensor design, yielding fundamentally new approaches for subsurface biomedical monitoring. Applications extend beyond biomedical systems and include uses such as wireless sensors for structural monitoring and communications devices. The industry partnerships will enable the research team to broadly disseminate results beyond the academic and research community. The project will also engage undergraduate students, while leveraging ongoing university programs that attract underrepresented students to engineering. A new senior/graduate-level project-based course that integrates research outcomes, and includes microwave integrated circuit design and fabrication, will be developed.
The outcomes of this award advance the understanding of the science and technology pertaining to biomedical sensors that can measure core body temperature, or more generally the temperature of tissues several centimeters below the surface of the skin. Anatomical disparities in human tissue are related to physiological variations, including temperature changes that may be caused by inflammation, increased cell metabolism, and tissue degeneration. An increased tissue temperature actually precedes the anatomical disparities which are undetectable by traditional clinical diagnostics. Moreover, the temperature observed at or near the skin surface using conventional contact or infrared thermometers can be significantly different from the temperature of underlying tissue. To probe further into the body, instruments known as microwave radiometers can be used. In this project new microwave antenna design techniques were investigated that are used to capture temperature-dependent electromagnetic energy emanating from the body; the amount of collected energy can be correlated to the inner body temperature using modeling approaches studied in this work. The new antenna designs are very thin (low profile) and flexible, such that they can conform to the surface of a non-planar object such as a human torso. In addition, the characteristics of the antennas can be tuned electronically, enabling real-time adjustment to differing antenna-skin contact conditions to achieve maximum energy capture. One focus of the research was in the area of nanotechnology, specifically nanometer-scale microelectronic devices and fabrication processes that provide the electronic tuning ability of the microwave antennas. Closely related to this work was an investigation in material science in order to optimize the properties of the thin-film materials that are the functional part of the tuning devices. Finally, in collaboration with the industry partner on the project (TriQuint Semiconductor) integrated circuits that are used to calibrate the biomedical sensor and can be embedded into the flexible substrates that support the antennas, were designed and demonstrated. The broader impacts of the project included advancements in the general field of microwave sensor design, yielding fundamentally new approaches for subsurface biomedical monitoring. Applications extend beyond biomedical systems and include uses such as wireless sensors for structural health monitoring and communications devices. The industry partnership enabled the research team to broadly disseminate results beyond the academic and research community. A new senior/graduate-level project-based course that integrated research outcomes, and includes microwave integrated circuit design and fabrication, was developed.
