Leveraging bound states in the continuum for advanced ultra-sensitive sensing technologies

Traditional sensing methods, such as ELISA, PCR, and electrochemical sensors, face challenges like limited sensitivity, high costs and complex sample preparation. In contrast, optical sensors, particularly surface plasmon resonance (SPR) and dielectric-based guided-mode resonance (GMR) sensors have emerged as promising alternatives. These sensors offer non-invasive measurements, remote readouts, and enhanced sensitivity. While SPR sensors benefit from high local sensitivity, they are limited by energy losses in the metal, reducing the overall quality-factor (Q). On the other hand, GMR sensors, which use low-loss dielectric materials, achieve higher Q factors but are constrained by their inability to effectively detect biomolecules located farther from the sensor surface. Recently, materials that support bound states in the continuum (BICs) have attracted attention for their potential to achieve infinite Q factors, resulting in ultra-narrow resonance linewidths, exceptional precision, and enhanced light-matter interaction. These features make BICs highly promising for sensing applications. This review offers an in-depth understanding of BICs, explaining their principles, including the topological nature of BICs, and exploring recent advancements in BIC-based refractive index sensing technologies. It focuses on material platforms such as dielectric, plasmonic, and hybrid materials that host BICs. Additionally, the review addresses challenges in the field and suggests potential solutions.