Wearable, Implantable, Parity-Time Symmetric Bioresonators for Extremely Small Biological Signal Monitoring

Wireless biosensors are essential for digital transformations in health and medicine. Chipless resonant antenna-based biosensors are affordable and tractable but are unsuitable for practical use because the common wireless sensing systems have low sensitivity caused by low quality factors. Herein, a parity-time (PT) symmetric wireless biosensor is demonstrated that can detect small biological signals such as tear glucose level (0.1-0.6 mm) for diabetes diagnosis and blood lactate level (0.0-4.0 mm) for lactic acidosis diagnosis. The characteristics of the PT-symmetric wireless sensing system are modeled by using an eigenvalue solution and input impedance, and the sensitivity enhancement at/near the exceptional point by using parallel inductance-capacitance-resistance resonators is experimentally demonstrated. 2000 times higher sensitivity for linear detection and 78% relative change for threshold-based detection are achieved. Furthermore, the proposed PT-symmetric wireless sensing system has sufficient tunability and robustness for use as a wearable/implantable device for monitoring small biological signals.