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

Abstract 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 m m ) for diabetes diagnosis and blood lactate level (0.0–4.0 m m ) 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.