Terahertz Metastructures for Noninvasive Biomedical Sensing and Characterization in Future Health Care

Terahertz radiation has promising potential in the biosensing field as a nonionizing, noninvasive, and label-free method, especially in the early detection of fatal diseases like cancer. Terahertz radiation is situated between the microwave and infrared regions of the electromagnetic (EM) spectrum and hosts many rotations, vibrations, and librations of biomolecules. However, it suffers from poor sensitivity, small penetration depth, low contrast, and long wavelength when applied to small biological sensing. These drawbacks provide a great opportunity to improve terahertz metamaterials. Periodic artificial structures can be designed to provide a localized EM field enhancement, leading to the increased interaction of the external stimuli with the analyte and forming a highly sensitive biosensor. This article reviews the fundamental and latest cutting-edge research works in biological sensing, particularly early cancer detection using terahertz metasurfaces. With a focus on recent advances, the first part covers examples of terahertz metasurfaces based on both classical and higher-order modes of plasmonic-like resonances. We then overview different methodologies for biosensing with high-Q-factor terahertz metasurfaces and novel enhancing techniques for low-concentration cancer biomarker solutions. Finally, we provide a summary and comparison of different approaches and the outlook for future health-care developments with terahertz metasensors