Screening and diagnosis of respiratory diseases using metamaterial based sensitive terahertz impedance spectroscopy

Utilizing LC resonant metamaterials (MM) for terahertz (THz) impedance spectroscopy has opened new avenues for detection of biomolecules and nanoparticles. A recent revelation highlights the pivotal role of coupling between MM resonance and Fabry-Pérot (FP) oscillations of the substrate. This interaction significantly influences the observed spectral shift ($\mathrm{\Delta F}$), thereby enhancing the overall sensitivity. In this work, we utilize the FP-MM optical decoupling physics for sensitivity enhancement to detect bio-particles at extremely low concentrations, thereby overcoming the particle detection limit. After implementing these innovations, we discovered that this technology can be leveraged to detect and screen patients infected with the omicron variant of SARS-CoV-2 and other lung related diseases using exhaled breath from patients. Upon achieving excellent agreement between simulations and experimental spectroscopic data, we have successfully detected and screened multiple respiratory-related diseases from the exhaled breath collected on the metasurface in a breathalyzer configuration. We obtained significant $\mathrm{\Delta F}$ even with ultra-low concentrations of bio-particles and demarcated the ranges of $\mathrm{\Delta F}$ for different lung diseases that do no overlap and are not constrained by any limit of detection. This work reveals new prospects for diagnosis and screening of multiple respiratory-related diseases with a single and prompt breath test.