Paper-based ultra-narrowband metamaterial absorber for low-cost terahertz sensing

Abstract The development of ultra-narrowband terahertz metamaterial absorbers has garnered increased attention due to their growing demand for high-performance terahertz sensors. However, the scalability of conventional absorbers for real-world applications such as sensors is limited by their reliance on expensive fabrication techniques and rigid substrates. Designing a sensor that is simple, flexible, low-cost, and environmentally friendly with high electromagnetic performance is a challenging task. As an emerging dielectric with low permittivity, mechanical flexibility, and biodegradability, paper helps to overcome this challenge. In this work, a paper-based perfect metamaterial absorber (PMA) is designed for low-cost sensing applications. The designed PMA exhibits a sharp near-unity absorption peak centred at 3.37 THz, a full-width half-maximum (FWHM) resonance peak of 2.28 GHz and an unprecedented quality factor of 1614.16. The uniform field distribution around the resonator indicates strong structural symmetry and stable resonance behaviour. Compared to state-of-the-art sensors, the proposed PMA achieves a remarkable sensitivity of 83.33 GHz RIU −1 and a high figure of merit (FoM) of 36.548 RIU −1 , demonstrating its high potential for high-precision sensing applications. The simplicity of the PMA structure, easy fabrication, cost-effectiveness, high spectral selectivity, and sensing capability enable this PMA as a strong candidate for future biomedical sensing technologies.