Soft and Flexible Wireless Epidermal Plaster Made by Laser-Induced Graphene

This letter introduces an epidermal antenna made of laser-induced graphene (LIG) that is designed for hosting sensors within the ultra-high frequency (UHF)-RFID band (860–960 MHz). The upper bound performance is identified through numerical simulations and it is just 4 dB lower than a copper counterpart. Comparative assessments reveal that a significantly wider trace width is necessary to mitigate the intrinsic power loss of LIG. Furthermore, this letter offers the first experimental demonstration of a LIG-based wireless flexible plaster, integrating a temperature-oriented radio frequency identification (RFID)
IC
encapsulated between skin-friendly elastomers. To address impedance matching challenges, a small coupled aluminum loop is employed to interface with the RFID
IC
. The device underwent testing on volunteers across different body parts with varying curvatures. Results indicate an averaged realized gain of −19 dBi, enabling a potential biophysical parameter collection from distances of up to 35 cm using a 3.2 W Effective Isotropic Radiated Power. This performance could support diverse applications in home care and sportswear. However, a notable efficiency degradation (5 dB) persists due to the interconnection of the antenna to the microchip transponder, presenting an ongoing challenge for optimization.