Multifunctional Terahertz Metasensor Based on Multi-Fano Resonance for Ultrasensitive Biodetection

Terahertz (THz) plasmonic resonance, particularly on artificially designed metasurfaces, has garnered considerable attention for enhancing the identification of biomolecules. However, the narrow-band response of these resonances hinders the comprehensive analysis of sample characteristic fingerprints, leading to false-positive results. Here, we developed a multifunctional THz plasmonic biosensor based on a broad-spectrum multi-Fano resonance capable of noninvasive and ultrasensitive detection of trace biological molecular particles, facilitating the differentiation and compositional analysis of two crucial neurotransmitters. The designed metasensor incorporates a multiresonator metasurface consisting of microantenna arrays to provide up to a remarkable 70-fold enhancement in near-field intensity across multiple spectral bands and demonstrate an exceptional sensitivity of 534 GHz per refractive index unit (RIU). Further investigations illustrate that the location and quantity of the resonant eigenpeaks can be arbitrarily adjusted by turning the structural parameters of the unit cell. Utilizing the advanced capabilities of the designed metasurface, we innovatively achieved synchronized qualitative and quantitative analysis of L-glutamic acid (Glu) while further conducting proportional analysis of a mixture of Glu and <tex-math notation="LaTeX">γ</tex-math> -aminobutyric acid (GABA). This endeavor naturally enriches the research on THz metasensors based on multiresonance, sparking exploration into novel approaches for identifying biomolecules and paving the way for sensitive and versatile small-scale THz spectroscopic devices.