Metasurface‐Driven Sensing in Terahertz Region: Principles, Applications, Fabrication, and Challenges

Abstract The terahertz (THz) spectral region offers unique advantages for sensing owing to its long wavelengths and low photon energies, enabling non‐destructive interactions with a wide range of materials, particularly suited for probing molecular vibrations and physical, chemical, and biological phenomena. However, conventional THz sensing methods often fail to detect ultrathin films or nanoscale molecular interactions, as their dimensions are significantly smaller than THz wavelengths. To address this challenge, THz metasurfaces, engineered structures with strong light‐material interactions, provide pronounced and tunable spectral features highly sensitive to environmental perturbations, thereby bridging the scale mismatch and significantly enhancing detection sensitivity. By leveraging tailored resonances and near‐field enhancement, THz metasurfaces facilitate sensing of biomolecules, ultrathin films, and even subtle changes in physical parameters such as temperature, strain, and pressure. This review presents a comprehensive overview of THz metasensors, structured around their fundamental physical mechanisms, key performance metrics, and sensing applications. In addition, it discusses diverse design strategies and fabrication approaches, including both mask‐based and maskless techniques, for the realization of high‐performance THz metasurfaces. With their exceptional sensitivity and versatility, THz metasensors hold significant promise as an enabling platform for ultra‐sensitive sensing and are poised to play a pivotal role in next‐generation sensing technologies.