Development of printed graphene-based Near Field Communication (NFC) antenna for temperature monitoring in food safety application

Food safety across the supply chain requires reliable real-time temperature monitoring, particularly for perishable products that are sensitive to environmental variations. Near Field Communication (NFC) offers a promising battery-less solution for real-time monitoring. However, conventional metal-based NFC tag antennas, typically fabricated using copper, are prone to oxidation, generate toxic waste during etching, and are unsuitable for integration into food packaging. This research focuses on the development and experimental validation of a fully printed, battery-less NFC tag antenna using carbon-based conductive materials, specifically hybrid graphene-silver (HGS), for food temperature monitoring applications. The scope of the study includes material characterization, antenna design and optimization, systematic impedance tuning, robustness evaluation in terms of flexibility and sensitivity, as well as integration with a flexible temperature sensor circuit.Three conductive materials, namely silver conductor (SC), hybrid carbon-graphene (HCG), and HGS, were characterized in terms of conductivity, surface morphology, roughness, and thickness. Four antenna designs (D1, D2, D3, and D4) were developed and simulated at 13.56 MHz, with only the optimized D4-HGS design proceeding to full robustness and system-level validation. Impedance tuning was systematically implemented using Optenni Lab to achieve resonance and minimal insertion loss.The optimized D4-HGS antenna, inkjet-printed on PET, achieved low antenna resistance (<50 Ω), sufficient inductance (~1.21 μH), and a 20% size reduction compared to the reference D1 antenna design. The antenna maintained a minimum read range of 1.3 cm under bending at a maximum bending angle of 190.9°, with a 38% improvement in read range when encapsulated with PET shrink wrap under moist conditions. Performance degradation on metallic surfaces was mitigated using an amorphous magnetic sheet, enabling tag detection up to 1.5 cm when attached to a metal surface.The fully flexible graphene-based NFC tag achieved temperature accuracy within ±3°C across cold, room, and hot conditions and demonstrated high reliability through validation with various food products.