Angle-Scanning and Size-Scaling Pixelated Quasi-BIC Metasurface Array for Broadband Terahertz Fingerprint Biosensing

Metasurface biosensing confronts a significant challenge in simultaneously achieving broadband response, high quality-factor (Q-factor), and ultrahigh sensitivity for specific trace-analyte detection at terahertz (THz) frequencies. Recently, quasi-bound states in the continuum (QBICs) metasurfaces provided enhanced light–matter interactions and ultrahigh sensitivity in narrow resonant bands. In this work, an angle-scanning QBIC metasurface array pixelated with just 5 × 5 scaling units is proposed to achieve an ultra-broad spectrum from 1 to 2.8 THz for fingerprint bio-detection. The symmetry-protected QBIC is excited by breaking the symmetry of copper block dimer resonator structures, achieving a Q-factor of 20 and a sensitivity of 500 GHz/RIU. A spectral step of approximately 10 GHz is demonstrated in this approach, and glutamic acid and glutamine are specifically detected, with detection limits reaching 15.4 μg/cm² and 14.7 μg/cm². This design provides a novel approach for achieving ultra-wideband, specific, and highly sensitive detection. This capability offers an efficient strategy for monitoring tumor metabolic biomarkers and paves the way for applications in early diagnosis and advanced broadband THz detection.