Comparative Evaluation of Impedance-Matching Techniques for Sustainable Laser-Induced Graphene (LIG) UHF RFID Antennas

As the demand for RFID-enabled systems grows, sustainability and circularity are becoming key drivers of innovation in tag and antenna design. Laser-Induced Graphene (LIG) offers a low-impact and recyclable alternative to metal conductors, enabling green, chemical-free, and energy-efficient fabrication compatible with eco-friendly substrates and material recovery. Yet, its high surface resistance limits radiation efficiency and complicates impedance matching with highly reactive UHF-RFID chips. This work presents a numerical and experimental comparison of distributed and lumped matching techniques for LIG dipoles, quantifying their contribution to power loss and overall efficiency. Distributed networks (e.g., T-match, notch) introduce large insertion losses (10–20 dB) due to differential-mode currents, while lumped configurations minimize energy dissipation and preserve material efficiency. The best trade-off between performance and sustainability is obtained with a single inductor (enabling realized gains around -5 dBi) for medium impedances, whereas for loads with a very low real part, an eventually reusable small metallic loop is required to ensure conjugate matching with negligible environmental impact. The proposed guidelines enable energy- and material-efficient LIG-based RFID antennas, offering a practical route toward eco-compatible and circular wireless systems that combine high RF performance with sustainable design principles.