A flexible dual-band microstrip grid array antenna-based terahertz biosensor for non-invasive diagnosis of basal cell carcinoma

Abstract This work introduces a compact and high-performance terahertz (THz) biosensor based on a microstrip grid array antenna (MGAA), tailored for the selective detection and early diagnosis of cancer within the 0.1–1 THz spectrum. The sensor is realized on an ultrathin (∼5 μm) polyimide substrate, offering both flexibility and conformability for seamless integration with non-planar biomedical platforms. The proposed MGAA operates in a dual-band mode, with distinct resonance frequencies at 0.17 THz and 0.37 THz, achieving reflection coefficients of –33 dB and –23 dB, respectively. These values confirm efficient impedance matching and minimal reflection losses, which are crucial for high-fidelity biosensing. The antenna exhibits an ultra-compact footprint of 300 × 350 μm, corresponding to deep subwavelength electrical dimensions of 0.1 λ × 0.117 λ at 0.1 THz, marking a substantial size reduction compared to reported THz sensors. This compactness is achieved through a rhombus-shaped grid configuration that effectively elongates the current path, thereby enhancing surface current confinement and improving sensing performance. Refractive index-based cancer detection is demonstrated across values ranging from 1.414 to 3.16, yielding sensitivities of 11.8 GHz RIU −1 and 26 GHz RIU −1 at the two resonances. The novelty of this work lies in combining ultra-miniaturization, dual-band operation, and flexible substrate integration, offering a promising route toward label-free, high-resolution, and non-invasive THz biosensing for early-stage cancer diagnostics.