Multifunctional Terahertz Biodetection Enabled by Resonant Metasurfaces.

Testing diverse biomolecules and observing their dynamic interaction in complex biological systems in a label-free manner is critically important for terahertz (THz) absorption spectroscopy. However, traditionally employed micro/nanophotonic techniques suffer from a narrow operating resonance and strong absorption band interference from polar solutions preventing seriously reliable, on-demand biosensor integration. Here, a multifunctional THz plasmonic biosensing platform by leveraging multiple interfering resonances from quasi-bound states in the continuum designed to noninvasively and in situ track the temporal evolution of molecules in multiple analyte systems, is proposed. In contrast to conventional microphotonic sensors, this platform demonstrates substantially broadband performance and reduced footprints, allowing for simultaneous detection of diverse molecular vibrant at multiple spectral points through robust near-field interactions. Furthermore, this sensor enables real-time analysis of amino acid absorption as water evaporates despite its strong overlapping absorption bands in the THz range. By utilizing the real-time format of the reflectance method to acquire a comprehensive spectro-temporal data collection, this approach supports developing a deep neural network to discriminate and predict the composition and proportion of multiple mixtures, obviating the need for frequency scanning or microfluidic devices. This approach offers innovative viewpoints for exploring biological processes and provides valuable tools for biological analysis.