Near-Field Communication for Battery-Free In Vivo Sensors

Traditional wireless sensors with bulky batteries require battery replacement or wireless charging which are not suitable for in vivo applications. Also, the leakage of battery chemicals is highly risky. Battery-free sensors are relatively small and easy to maintain. In this paper, the magnetic induction-based Near-Feild Communication (NFC) is employed to charge and communicate with intra-body sensors. Cell phones with NFC modules can be leveraged as readers to interact with in vivo sensors. In this way, the system does not require additional external wireless devices. The collected health-related data can be processed by cell phones directly. The invivo sensors are powered up by using magnetic induction-based wireless energy transfer and health-related data are transmitted by sensors using backscatter communications. This paper introduces the system architecture and associated wireless simulations and empirical results. The inhomogeneous human body is considered using a layered-media model. Electromagnetic simulations are performed in COMSOL Multiphysics to study the communication range with signals from 100 kHz to 100 MHz in various environments. The results provide guidelines on the design of in-vivo battery-free sensors in terms of power consumption, coil size, and implanted depth.