image: Figure | Design and operation of the on-chip THz metasensor. a, The metasensor integrates THz generation, THz-molecule interaction, and signal detection on a single platform. The metasurface converts the guided THz wave into a surface-confined spoof surface plasmon polariton mode, enhancing its interaction with analytes for fingerprint sensing. b, Samples are deposited onto the metasensor by drop-casting and drying. The insets show the molecular structures and fingerprint spectra of the four representative biomolecules and their mixture. c, Photograph of the fabricated metasensor alongside a one-yuan coin for scale.
Credit: Yao Lu et al.
The ability to reveal and quantify the molecular composition of complex samples in a label-free and nondestructive manner at the point of use is increasingly important for precision medicine and pharmaceutical analysis.
Terahertz (THz) spectroscopy offers a distinctive approach because many molecules exhibit fingerprint absorption features in the THz band, enabling label-free and nondestructive identification. However, conventional THz spectroscopy systems remain bulky and vulnerable to environmental disturbances, while existing on-chip sensors mainly address the qualitative detection of single analytes, leaving a gap in the quantitative analysis of complex mixtures.
In a new paper published in Light: Science & Applications, a team of scientists led by Professor Qiang Wu, Associate Professor Yao Lu, and Professor Jingjun Xu from Nankai University, together with Professor Baohua Jia from RMIT University, developed an on-chip THz metasensor for quantitative multi-component biomolecular identification.
By bringing THz generation, propagation, analyte interaction, and signal detection together on a single lithium niobate (LN) wafer, the researchers created a compact sensing platform capable of identifying molecules from their characteristic fingerprints and quantitatively analyzing multiple components in mixtures. The resulting platform provides a promising route toward portable THz fingerprint sensing for real-world molecular analysis.
The on-chip metasensor is built on a self-supporting LN wafer patterned with a periodic metasurface array. The LN wafer serves as the medium for THz generation, propagation, and signal detection, while the metasurface array concentrates and guides broadband THz waves along the sensing surface. This surface confinement strengthens the interaction between THz waves and analytes and extends the effective interaction path.
Xitan Xu, the first author of the study, summarizes the key aspects of the metasensor:
“We designed the metasensor with three key objectives: (1) to integrate the essential THz functional modules on a single platform; (2) to enhance broadband THz–analyte interactions; and (3) to quantitatively resolve the contributions of individual components in mixtures.”
To demonstrate the capability of the metasensor, the researchers investigated four representative biomolecules, including two amino acids and two disaccharides. The metasensor identified each biomolecule from its characteristic THz fingerprint and, when multiple biomolecules were mixed, quantitatively resolved their individual spectral contributions through spectral decomposition.
This design establishes a chip-scale strategy for reading and quantifying multiple molecular signatures in complex samples, opening new avenues for compact THz fingerprint sensing.
“Further combining the metasensor with compact optical modules, microfluidic sample-handling systems, and intelligent data-processing algorithms could pave the way for next-generation integrated THz analytical platforms for precision healthcare, smart pharmaceutical manufacturing, and real-time biochemical process monitoring,” the scientists forecast.
Journal
Light: Science & Applications
Article Title
On-chip terahertz metasensor for quantitative multi-component biomolecular identification