An Ultraminiaturized Multiband Metasurface Absorber Toward Multifold Sensing Applications in Healthcare

Terahertz (THz) sensors based on metasurface (MS) absorbers have shown lot of promise in healthcare sector because of their high quality (Q)-factor surface plasmon resonance (SPR) characteristics. However, single-band functionality of these sensors might lead to false-positive result. In this article, we present an angularly stable (up to ±40°) triple-band microscale MS absorber in THz domain and its utility to unprecedented applications toward multifold sensing. With ultranarrow linewidth and close-to-perfect absorbance, the suggested MS absorber delivers near-perfect triple-band absorption around 1.675, 3.504, and 5.694 THz. The absorption feature is validated by an in-house equivalent circuit model (ECM). Owing to the ultranarrow absorption peaks in the THz domain, the intended metasensor demonstrates high sensitivity and figure of merit (FoM) toward variations in refractive index (RI) of the analyte layer; thereby, finding it capable to detect and distinguish various types of cancers, tumors, viruses, tuberculosis, malaria, hemoglobin content in blood, and glucose content in water. The respective half-power bandwidths of 0.109, 0.206, and 0.370 THz result into high Q-factors of 15.367, 17.009, and 15.389. It offers an estimated sensitivity of 0.363, 0.991, and 1.636 THz/RIU together with FoM of 3.330, 4.809, and 4.421 RIU⁻¹, respectively, at the three absorption peaks, covering a wide range of refractive indices (1.3–1.5). The designed meta-atom is ultraminiaturized and low profile with overall footprint dimension of $0.128\lambda \times 0.128\lambda \times 0.013\lambda $ at 1.675 THz.