Wearable UHF RFID Sensor-Tag Based on Customized 3D-Printed Antenna Substrates

The combination of radiofrequency identification (RFID) technology with 3D-printed structures is very appealing to design new RFID-based smart but cost-effective devices. In this paper, two different 3D-printed devices in the RFID framework are designed, realized, and tested. In particular, since permittivity and loss tangent of the printed substrate depend on the volume fraction of air in the host material, the first proposed device is purposely a T-resonator-based system suitable for the dielectric characterization of 3D-printed substrates in UHF RFID band, realized in 3D-printing technology itself. Based on the obtained results, the second device is a compact 3D-printed wearable antenna feeding a UHF RFID sensor tag designed to passively sense and retrieve the human body temperature. Both devices have been realized by combining 3D-printed plastic elements and conductive parts and then tested so to demonstrate the aptness of 3D-printing technology in designing RFID devices.