Integrated microphotonic platform for highly sensitive virus detection

Chip-scale micro-photonic biosensors have matured significantly over the past two decades, with various platforms developed for detecting biomarkers, including proteins in biological fluids. The COVID-19 pandemic has further accelerated research in virus detection, leading to the development of resonant and interferometric biosensors for identifying viruses like SARS-CoV-2. Despite these advancements, there remains a need for technical solutions that ensure point-of-care features such as low cost, rapid response, and low limit-of-detection (LoD). This paper presents an integrated silicon nitride microphotonic platform based on ring resonator technology, specifically designed for highly sensitive virus detection. The sensors, fabricated using strip and slot waveguides, are tested under flow conditions using ethanol and BSA-antiBSA solutions to evaluate bulk and surface sensitivity. The results indicate that the slot waveguide-based ring resonators exhibit the highest sensitivity. The platform uses functionalization protocols to immobilize specific antibodies for detecting SARS-CoV-2. The sensor successfully identifies the target analyte at concentrations as low as 1.5 nM, with a LoD of 36 pM using in situ functionalization, underscoring the importance of antibody orientation through an intermediate protein A layer. These results demonstrate the platform's potential for rapid and sensitive virus diagnosis and represent a significant step toward the development of portable, point-of-care diagnostic technologies for infectious disease monitoring.