Varactor-tunable RFID-based wireless programmable frequency selective surface as a smart shield for implanted medical devices

Modern Implantable Medical Devices (IMDs) feature wireless capabilities that enable remote monitoring and device programmability. However, this increased connectivity also introduces vulnerabilities to both cyber and physical threats, potentially endangering patient safety. This study presents a novel, miniaturized design of an epidermal Radio-Frequency Identification (RFID)-based wireless programmable Frequency Selective Surface (FSS) to shield IMDs from unauthorized users while ensuring secure communication. Compared to previous studies, the proposed design reduces power consumption using varactor diodes instead of PIN diodes. Simulation results demonstrate the effectiveness of the shield in attenuating Electromagnetic Interference (EMI) in the Medical Implant Communication Service (MICS) band by 49 dB, as well as its programmability to achieve transparency. Four dipoles surrounding the finite FSS allow for RFID-based wireless programmability. This solution represents a significant advancement in the cyber and physical protection of IMDs, being at the same time the first example of a wireless programmable FSS.