Wearable chipless radio-frequency identification tags for biomedical applications: a review

Wearable sensing technology and body-centric wireless systems have received widespread attention due to their tremendous prospective in e-health, the Internet of Things (IoT), and smart cities. Low-cost textile antennas for body-centric radio-frequency identification (RFID) sensing technology are the future for such wearable sensing systems. The antennas can sustain bending and stretching and offer a maintenance-free communication link with the human body, environment, and IoT infrastructure. Its sensing technology provides the seamless real-time wireless monitoring of important physiological signals. Understanding its significance in emerging applications, this article reviews wearable passive RFID tag sensors that monitor various physical parameters. The primary goal of these research works is to design RFID sensors and test their performances in various environmental conditions. Chip-based RFID sensors are too expensive for mass deployment, hence, chipless RFID tag sensors have become a low-cost and maintenance-free alternative, addressing market demands for the emerging IoT, where trillions of such sensors will be used. Observing the significance of the technology, a few important design parameters, such as tag radar cross section (RCS) and various form factors of tag antennas, are examined in this article. The article also presents some emerging applications of the developed sensors.