High-performance, robust, and compact grating-based surface plasmon resonance sensor for biosensing: utilizing a tunable laser

Prism-based surface plasmon resonance (SPR) sensor is a powerful label-free analytical technique used in food safety, medical diagnostics, and environmental monitoring. It is currently mainly used in centralized laboratories due to its size and price. Grating-based SPR sensors offer a cost-effective and miniaturized alternative for point-of-care applications. However, grating-based SPR sensors have limited performance and robustness for practical use. In this study, we present a high-performance, robust, and compact grating-based SPR sensor enabled by a tunable laser working at normal excitation and readout incidence. This configuration eliminates the spectral analysis and moving parts, thereby enhancing the robustness of the instrumentation. The sensor was designed, optimized, and analyzed using COMSOL Multiphysics, and then fabricated through nanoimprinting lithography. Both computationally and experimentally, we demonstrated the SPR dip splitting at non-zero incidence, which was lacking in previously reported grating-based SPR sensor studies. The sensor was tested with glucose solutions, achieving a sensitivity of 1101.6 m/RIU. The figure of merit of the sensor was 229.5 surpassing other reported grating-based SPR sensors by one order of magnitude. The experimental results were in good agreement with the simulations. We also demonstrate its performance in detecting low concentrations of glucose and creatinine with the limit of detection of 14.2 mM and 19.1 mM, respectively. These results show the potential of our high-performance, portable SPR sensor for point-of-care applications.