Ultrasensitive Terahertz Biodetection Enabled by Quasi‐BIC‐Based Metasensors

Abstract Advanced sensing devices, highly sensitive, and reliable in detecting ultralow concentrations of circulating biomarkers, are extremely desirable and hold great promise for early diagnostics and real‐time progression monitoring of diseases. Nowadays, the most commonly used clinical methods for diagnosing biomarkers suffer from complicated procedures and being time consumption. Here, a chip‐based portable ultra‐sensitive THz metasensor is reported by exploring quasi‐bound states in the continuum (quasi‐BICs) and demonstrate its capability for sensing low‐concentration analytes. The designed metasensor is made of the designed split‐ring resonator metasurface which supports magnetic dipole quasi‐BIC combining functionalized gold nanoparticles (AuNPs) conjugated with the specific antibody. Attributed to the strong near‐field enhancement near the surface of the microstructure enabled by the quasi‐BICs, light‐analyte interactions are greatly enhanced, and thus the device's sensitivity is boosted significantly. The system sensitivity slope is up to 674 GHz/RIU, allowing for repeatable resolving detecting ultralow concentration of C‐reactive protein (CRP) and Serum Amyloid A (SAA), respectively, down to 1 pM. The results touch a range that cannot be achieved by ordinary immunological assays alone, offering a novel non‐destructive and rapid trace measured approach for next‐generation biomedical quantitative detection systems.