RFID Antennas for Body-Area Applications: From Wearables to Implants

Radio-frequency identification (RFID) technology has recently attracted significant interest in the realm of body-area applications, including both wearables and implants. The presence of the human body in close proximity to the RFID device creates several challenges in terms of design, fabrication, and testing, while also ushering in a whole new realm of opportunities for health care and other body-area applications. With these factors in mind, this article provides a holistic and critical review of design challenges associated with body-area RFID technologies, including operation frequencies, influence of the surrounding biological tissues, antenna design and miniaturization, and conformance to international safety guidelines. Concurrently, a number of fabrication methods are discussed for realizing flexible, conformal, and robust RFID device prototypes. The article concludes by reviewing transformative RFID-based solutions for wearable and implantable applications and discussing the future opportunities and challenges raised. Notably, this is the first time that a comprehensive review has been presented in the area of RFID antennas for body-area applications, addressing challenges specific to on-/in-body RFID operation and spanning a wide range of aspects that include design, fabrication, testing, and, eventually, applications and future directions. As such, the utmost aim of this article is to be a unique point of reference for experts and nonexperts in the field.