Integrating High Frequency Whispering-Gallery-Mode Phononic Cavities with Efficient Electrically-Small Antennas: Pushing the Limits of Wireless Passive Micro-Sensing

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This project aims to explore and combine novel micro-scale resonator designs with extremely small antennas to build a wireless sensing platform that does not require power sources and takes advantage of the economy scale in delivering exceptional performance at very low price-points. This platform, once realized, is believed to make a significant impact on medical sensing paradigms by offering flexibility in remote and nonintrusive measurement of patients vital signs. Despite the tremendous technological progress made in the field of microelectronics during the past few decades, there exists a gap between the scale of sensing apparatus used in medical industry and the state-of-the-art in the field of miniaturized sensors. Specifically, the devices monitoring respiration rate and breathing pattern are inconvenient for the patients due to excessive wiring. The platform proposed in this project can significantly scale down the size of the equipment required for monitoring breathing rate. The same technology can be adapted for continuous monitoring of the temperature (including the core body temperature), the heart rate, blood pressure, oxygen intake, etc. without the need for changing the battery. The data collection can be achieved by a simple and small gadget that could communicate with smartphones. The principal investigators are participating in the NSF-supported Career Advancement Mentoring Program for Young Entrepreneur and Scholars Program (CAMP-YES) and the Research and Mentoring Activities (RAMA) program at the University of Central Florida, both of which promote research experience for underrepresented undergraduate students. The resources developed in this project will assist the principal investigators in furthering their contributions to these programs by recruiting students to engage in this research. The main objective of this project is to enable extremely-small wireless passive sensors by exploring exceptionally high quality factor (Q) piezoelectric-based high-frequency resonators integrated with ultra-small highly-efficient antennas. In this work, for the first time, whispering-gallery mode phononic cavities in a piezoelectric-on-ultrananocrystalline diamond platform will be demonstrated with the goal of achieving high coupling factor and high quality factor at high frequencies around 1 GHz. The whispering gallery mode is chosen to evade the anchor-loss (a major source of energy loss) and the diamond substrate is chosen to minimize the effect of internal friction losses at high frequencies. Such large values of coupling and Q could enable extremely-small size ( 1 cm x 1 cm including the antenna) wireless sensors with a readout range of a few meters. The tasks include: 1) Studying the physics of loss in high frequency piezoelectric-on-diamond resonators, 2) Implementation of whispering-gallery mode phononic cavities in the thin-film piezoelectric-on-diamond platform, 3) Integration of the phononic cavities with highly-efficient electrically-small antennas to develop passive wireless sensors. Such sensors can be orders of magnitude smaller than other wireless sensors operating at similar frequencies. Successful demonstration of extremely small wireless sensors targeted in this project will have a significant impact on a wide range of remote sensing applications including medical health monitoring and diagnosis, environmental monitoring, and industrial control.