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.