Performance and Durability of Thread Antennas as Stretchable Epidermal UHF RFID Tags

Epidermal sensors based on battery-less Radiofrequency Identification (RFID) aim at collecting biophysical parameters with a high level of comfort for the user. This paper investigates the performance and durability of epidermal RFID tags, equipped with a self-tuning RFID IC, that are based either on copper wires or conductive yarns. The tags are deployed onto an ultra-thin stretchable and transparent substrate to achieve comformability to body discontinuities. A statistical analysis on volunteers showed that, in the whole UHF band (860-960 MHz), reliable read ranges of 1 m are easily achieved while up to 2 m can be reached in some favorable configurations. Both tags withstand wear, mechanical stress due to the movements of the body, sweating, and water. In particular, the tag made of conductive yarn lasts for more than 20 days. This new family of epidermal tags is moreover suitable for low-cost and large-scale manufacturing through the widely available machines used for wire-laying, bending, and shaping.