Ultrasensitive Terahertz Metasurface Biosensor Based on Quasi-Bound States in the Continuum

TL;DR

This paper introduces an ultrasensitive terahertz metasurface biosensor utilizing quasi-bound states in the continuum to achieve high sensitivity and low detection limits for biochemical sensing.

Contribution

The work demonstrates a novel QBIC-based metasurface biosensor with record sensitivity and detection limits, advancing THz biosensing technology.

Findings

Achieved a sensitivity of 492 GHz/RIU for cysteine detection.

Detected cysteine at concentrations as low as 0.00025 mg/mL.

Enhanced light-matter interaction through QBICs improves biosensor performance.

Abstract

The terahertz (THz) spectral regime offers unique opportunities for next-generation biochemical sensing due to its non-destructive, label-free probing capability and strong sensitivity to molecular vibrations. However, conventional THz biosensors remain hampered by intrinsically low-quality factors and limited sensitivity, severely restricting their utility for trace-level biochemical and chemical detection. Here, we report an ultrasensitive THz metasurface biosensor that harnesses quasi-bound states in the continuum (QBICs) with sharp resonances and enhanced light-matter interactions to overcome these limitations. As a proof of concept, the device achieves label-free detection of a sulfur-containing amino acid cysteine, with an ultrahigh sensitivity of 492 GHz/RIU and an ultralow detection limit down to 0.00025 mg/mL. The synergy between QBIC-induced field confinement and meticulous structural optimization of the metasurface underpins this performance, marking a significant advance over conventional THz metasurface biosensing schemes. These results establish QBIC-based metasurfaces as a promising platform for ultrasensitive and high-precision biochemical and chemical sensing, with broad implications for medical diagnostics, food safety, and environmental monitoring.