Numerical investigation of an SNG metamaterial-based multiband THz biosensor for early non-melanoma skin cancer detection

This article presents a high-sensitivity terahertz (THz) metamaterial absorber–based biosensor for the early detection of non-melanoma skin cancer through refractive index sensing. The proposed sensor consists of a pair of concentric gear-shaped resonators (GSRs) fabricated from gold and integrated on a polyimide dielectric substrate, forming a compact unit cell with a periodicity of 75 µm. The designed metasurface exhibits multi-band resonance characteristics, with the highest absorption reaching 99.99 % at a resonance frequency of 1.4485 THz, demonstrating near-perfect absorption behavior. The structure also achieves a high-quality factor (Q-factor) of 1116.8, indicating strong electromagnetic confinement and excellent spectral selectivity. Comprehensive parametric analyses are performed to optimize the geometrical parameters and evaluate the stability of the absorption response under different polarization angles. The sensing performance is investigated by varying the refractive index of the surrounding medium within the biologically relevant range of 1.35–1.39, corresponding to normal and cancerous skin tissues. The proposed biosensor exhibits a clear and consistent resonance shift with refractive index variation, achieving a maximum sensitivity of 190 GHz/RIU and a figure of merit (FoM) of 146.49, confirming its capability to detect subtle dielectric variations in biological samples. Furthermore, the absorption response remains stable under polarization variations, highlighting the robustness of the design for practical sensing environments. These results demonstrate that the proposed THz metamaterial absorber provides a compact, highly sensitive, and reliable platform for label-free biomedical refractive index sensing, offering promising potential for early-stage skin cancer detection in terahertz diagnostic systems.