Parity-Time Symmetric Wireless Telemetry Systems for Implantable Microsensors

随着世界迅速老龄化，能够准确和持续地监测身体器官的生理参数(例如压力)，能够有效地管理许多慢性病。2010年，美国已有4030万65岁及以上的老人(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，用于敏感、长期地监测人体内的生理参数，这些参数是管理慢性疾病(如眼病、心力衰竭或脑损伤)和提高患者生活质量所必需的。无电池植入式传感器在临床应用中发展迅速，因为它们具有零功耗的优势，有可能实现长寿命和免维护操作。然而，这些植入式传感器的主要挑战之一在于如何使用射频信号准确而稳健地从电损耗小型传感器中检测出生理参数。提出的基于奇偶时间(PT)对称的无线传感器系统将提供一种新的方法来处理植入式微传感器和外部读取器之间的射频询问，旨在实现高灵敏度、高传感分辨率和大调制深度的无线传感和检测。这一拟议项目的教育影响也将是巨大的。由于微/纳米设备、传感器和电路的视觉吸引力，综合推广计划将是有效的。PIS将在密歇根科学中心和韦恩州立大学的现有渠道开发新的课程和推广活动，包括ReBUILDetroit计划和Richard Barber跨学科研究计划，以在底特律地区招募代表不足的少数族裔。该研究项目的目标是通过实验演示射频和微波电子学中的广义PT对称理论，以及它们在高性能无线传感器中的预期应用。由于集肤效应、介质损耗、涡流等有限的空间和功率消耗，无源无线微纳传感器的灵敏度和信噪比往往受到低模品质因数(Q因子)的限制。PT对称性(空间反转和时间反转对称性)的概念最早是在量子理论中发现的，近年来已成为光学、声学、电磁学等基础物理领域的一个活跃研究领域。在生物遥测和无线传感应用(13.56 MHz-低GHz)方面，还没有研究过等效电路拓扑符合PT对称性的遥测系统。这种新的遥测系统虽然具有非厄米哈密顿量，但可能显示出纯实的本征频率，导致尖锐和深度的共振，其有效品质因数(Q因数)超出了被动系统的限制，在被动系统中，传统的环状天线被部署为读取器。尖锐的窄带反射峰是遥测传感器系统长期追求的目标，因为它对更好的检测和低累积噪声具有重要意义。如果成功，提出的PT对称无线传感器系统将解决无线微电子机械和纳米技术传感器中长期存在的Q因数低和灵敏度有限的问题，这些传感器由微型化的电感-电容(LC)谐振器组成。这项拟议的研究将推进生物医学植入物、可穿戴电子学、医疗诊断、医疗物联网(IoT)、微波成像、无线通信和非厄米PT对称物理的基础知识。

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.