Metasurface biosensors across microwave and optical regimes-electromagnetic design, fabrication, and biosensing applications

Label-free detection of biomarkers has garnered considerable research interest, particularly with the advent of advanced sensing platforms, like metasurfaces. Metasurfaces are two-dimensional metamaterials consisting of an array of metal–metal or metal–dielectric-based structures with fine-tuned shapes and sizes at the nanoscale (∼10−9 m). This paper aims to discuss current knowledge and several recent advancements in metasurface biosensing such as reconfigurable metasurface, quasi-BIC, ML-assisted metasurface design, and microfluidic integration of sample movement for real-time monitoring applications at microwave and optical frequencies. The principle behind the operation of the metasurface biosensor is based on the change in dielectric constant at microwave frequencies and refractive index or surface plasmon resonance at optical frequencies for the biomolecular substance. Based on the parametric change in the corresponding frequencies, the biosensor detects abnormalities in the biological substance. In this review, the fundamental design, functional materials that interact with electromagnetic waves, dynamics in sensing mechanism linking field confinement, modal perturbation, resonance shift phenomenon, fabrication techniques and their potential challenges, roadmap to future advancements, and real-time challenges in biosensing applications for microwave and optical frequencies are discussed.