Parity-Time Symmetric Wireless Telemetry Systems for Implantable Microsensors

随着世界迅速老龄化，准确和连续监测身体器官中的生理参数（例如压力）的能力使得能够有效管理许多慢性疾病。2010年，美国65岁及以上的老年人已达4030万人（占总人口的13%）。预计到2050年，这一比例将达到20.9%。在这项研究中，将研究一种新型的无线生物医学植入物，用于对人体生理参数进行敏感的长期监测，这是管理慢性疾病（例如眼疾，心力衰竭或脑损伤）和改善患者生活质量所需的。无电池植入式传感器在临床应用中增长迅速，因为它们具有零功耗的优势，可能允许长寿命和免维护操作。尽管如此，这些植入式传感器的主要挑战之一在于如何使用射频（RF）信号准确且鲁棒地检测来自电损耗小型传感器的生理参数。提出的奇偶时间（PT）对称无线传感器系统将使新的方式来操纵植入式微传感器和外部读取器之间的RF询问，旨在实现无线传感和检测具有高灵敏度，高传感分辨率，和大调制深度。这一拟议项目的教育影响也将是重大的。由于微/纳米器件、传感器和电路的视觉吸引力，综合推广计划将是有效的。研究所将在密歇根科学中心和韦恩州立大学的现有渠道中开发新的课程和外展活动，包括ReBUILDIT计划和Richard Barber跨学科研究计划，以招募底特律地区代表性不足的少数民族。以及它们在高性能无线传感器中的预期应用。无源无线微/纳传感器的灵敏度和信噪比往往受到低模态品质因数的影响由于集肤效应、介电损耗、涡流等因素的影响，空间和功率损耗有限。PT对称的概念（空间反演和时间反演对称性）最早是在量子理论中发现的，最近已成为基础物理学中的一个活跃研究领域，包括光学，声学，和电磁学。一个遥测系统，其等效电路拓扑结构遵守PT对称性尚未被调查的生物遥测和无线传感应用（13.56 MHz -低GHz）。这种新的遥测系统，虽然具有非厄米哈密顿，可以表现出纯粹的真实的本征频率，导致尖锐和深的谐振，有效的品质因数（Q因子）超出了无源系统的限制，其中传统的环形天线部署作为阅读器。尖锐的窄带反射峰一直是遥测传感器系统长期追求的目标，因为其对上级检测和低累积噪声的实质性影响。如果成功的话，所提出的PT对称无线传感器系统将解决长期存在的问题，低Q值和有限的灵敏度在无线微机电和纳米技术传感器，由电感电容器（LC）谐振器与小型化的足迹。这项研究将推进生物医学植入物，可穿戴电子产品，医疗诊断，医疗物联网（IoT），微波成像，无线通信和非Hermitian PT对称物理学的基础知识。

The capability to accurately and continuously monitor physiological parameters (e.g. pressures) in body organs enables effective management of many chronic diseases, as the world is ageing rapidly. In the year 2010, US already had 40.3 million people aged 65 and older (accounting for 13 percent of total population). The ratio is projected to reach 20.9 percent by 2050. In this research, a novel class of wireless biomedical implants will be investigated for sensitive, long-term monitoring of physiological parameters in human bodies, needed for managing chronic diseases (e.g. eye disease, heart failure, or brain injury), and for improving patients' quality of life. Battery-free implantable sensors have been growing rapidly in clinical uses because they have advantages of zero power consumption, potentially allowing for long-lifetime and maintenance-free operation. Nonetheless, one of the primary challenges for these implantable sensors lies in how to accurately and robustly detect physiological parameters from electrically-lossy small sensors using radio-frequency (RF) signals. The proposed parity-time (PT)-symmetric wireless sensor system will enable new ways to manipulate the RF interrogation between the implantable microsensor and the external reader, aiming to realize wireless sensing and detection with high sensitivity, high sensing resolution, and large modulation depth. The educational impact of this proposed project will also be significant. The integrated outreach program will be effective due to the visually appealing nature of micro-/nano-devices, sensors, and circuits. The PIs will develop new courses and outreach activities in Michigan Science Center and Wayne State University's established channels, including ReBUILDetroit Program and Richard Barber Interdisciplinary Research Program, for recruiting under-represented minorities in the Detroit area.The goal of this research project is to experimentally demonstrate the generalized PT-symmetry theory in RF and microwave electronics, as well as their envisaged applications in high-performance wireless sensors. The sensitivity and signal-to-noise ratio (SNR) of the passive wireless micro-/nano-sensors are often hindered by low modal quality factor (Q-factor), due to the limited space and power dissipations associated with the skin effect, dielectric losses, eddy currents, and etc. The concept of PT-symmetry (spatial inversion and time-reversal symmetry) was first discovered in quantum theory, and has recently become an active research area in fundamental physics, including optics, acoustics, and electromagnetism. A telemetry system with its equivalent-circuit topology obeying the PT-symmetry has not yet been investigated for biotelemetry and wireless sensing applications (13.56 MHz - low GHz). This new telemetry system, although having a non-Hermitian Hamiltonian, may exhibit purely real eigenfrequencies that lead to sharp and deep resonances, with the effective quality factor (Q-factor) beyond limitations for passive systems, in which conventional loop-antenna is deployed as a reader. A sharp, narrowband reflection peak has been a long-sought goal for telemetric sensor systems, because of its substantial implications for superior detection and low cumulative noises. If successful, the proposed PT-symmetric wireless sensor system will resolve the long-standing problem of low Q-factor and limited sensitivity in wireless microelectromechanical and nanotechnological sensors, composed of inductor-capacitor (LC) resonators with miniaturized footprints. This proposed research will advance fundamental knowledge in biomedical implants, wearable electronics, medical diagnosis, healthcare internet of things (IoT), microwave imaging, wireless communication, and non-Hermitian PT-symmetric physics.