Flexible graphene-based metasurfaces for ultra-sensitive detection of basal cell carcinoma

This study investigates electrically tunable flexible graphene-based metasurfaces for the ultra-sensitive detection of Basal Cell Carcinoma (BCC). Three geometrical configurations—planar, inward-bending, and outward-bending—are analyzed under varying chemical potentials (μc = 0.2–1.4 eV) to differentiate healthy skin from malignant tissues. Key sensing parameters, including resonance frequency, quality factor (Q), frequency shift (Δf), discrimination index (DI), figure of merit (FOM), detection limit (DL), and penetration depth (δ), are evaluated. Among the proposed designs, the inward-bending metasurface exhibits the best overall sensing performance, achieving a sensitivity of 3920 GHz/RIU, a maximum FOM of 5.04 RIU⁻1 at μc = 1.4 eV, and a high Q-factor of 384.98 at μc = 0.2 eV. It also provides an optimized penetration depth of 27.03 μm with DL = 0.2027 RIU at μc = 1 eV, enabling enhanced interaction with superficial tissue layers. In addition, a frequency shift of 196 GHz and a discrimination index of 6.19 dB enable accurate tissue classification. Although the planar metasurface achieves the highest absolute sensitivity of 5600 GHz/RIU and a larger frequency shift of 280 GHz, its low Q-factor (≈30.89) limits sensing resolution. The outward-bending structure demonstrates intermediate performance. Furthermore, near-perfect absorption of 99.9% at 9.12 THz is obtained for the inward-bending design, indicating strong field confinement and enhanced light–matter interaction. These findings demonstrate that the inward-bending graphene-based metasurface is a promising platform for high-resolution, non-invasive THz sensing and early skin cancer diagnosis.