High-performance demultiplexer-based lab-on-bio-chip sensor leveraging silicon photonics for point-of-care detection of hemoglobin and blood calcium ion levels

This article presents what we believe to be a novel lab-on-bio-chip (LoBC) sensor design employing a silicon-insulator-silicon (SIS) configuration capable of detecting refractive index changes of two distinct analytes in a single sensor. The sensor marks the first instance where an alternative plasmonic material is utilized for a multi-analyte sensor. The use of silicon photonics in the design offers significant advantages, including CMOS compatibility, high optical tunability, the benefit of utilizing the mature silicon fabrication infrastructure, and advanced electronic-photonic co-design, resulting in cost-efficient and scalable production. The proposed LoBC sensor demonstrates a sensitivity of 1273.5788 nm/RIU and a detection limit of 7.8518 × 10^-7 RIU. To the best of our knowledge, this study is the first to introduce sensitivity to volume ratio (SVR), a novel metric for evaluating the sensor's performance. The SVR value for our sensor is 8.58190 × 10^-6 nm^-2 · RIU^-1, highlighting its efficiency in compact and sensitive designs. This innovative sensor is employed to detect the concentration level of calcium ions (Ca²⁺) and hemoglobin in blood. The sensor attains a 0.4312 nm and 2.206 nm shift in the transmission peak for each 1 mg/dL and 1 g/dL change in Ca²⁺ and hemoglobin concentration, respectively. Our study showcases the first-time application of an SIS sensor in determining Ca²⁺ concentration in blood. The benefits of CMOS-compatible silicon used in our LoBC sensor, along with the high sensitivity and compactness, position our biosensor as a robust platform for addressing the growing demand for advanced multi-analyte detection in hematology and in vitro diagnostics.