Surface Plasmon Resonance (SPR) is a wave phenomenon occurring at a metal-dielectric interface. A SPR-based biosensor operates by monitoring changes in the refractive index close to the interface that are produced in response to the interaction between the analyte and the receptors immobilized on the metal’s surface. The performance of these sensors depends on many parameters, including channel geometry, material properties and parameters related to chemical interaction between the analyte and immobilized receptors. This paper presents an integrated model that predicts the sensitivity of an SPR-based sensing platform under the Kretschmann configuration. The model uses the analytical solution of the differential equations that describe the analyte-bioreceptor interaction to correlate changes in analyte concentration to changes in refractive index at the sensing surface. These results are then connected with COMSOL simulations that relate changes in refractive index to changes in the SPR reflectivity curves. The resultant relations are integrated and the model is evaluated under different scenarios. This model will aid in the optimization of assay parameters prior to experimentation for maximum sensitivity; saving both time and expensive chemical reagents during the experimental phase.
Surface Plasmon Resonance (SPR) is a wave phenomenon occurring at an interface between a dielectric and a metal. SPR has applications in label-free biodetection systems, where advances in microfabrication techniques are fostering the development of SPR-based labs-on-a-chip. This work presents a numerical analysis for the excitation of SPR using Kretschmann's configuration. With a SiO2 prism, an Au metal layer, and water as the dielectric, the system is made to be compatible with a post-CMOS microfabrication process. The results obtained from both theory and software simulation show that for a light source at 633 nm, a 50 nm thick Au film is optimal, with the reflectivity falling to a minimum of ~2% at an angle of ~68.5°, due to maximum electromagnetic SPR coupling. Simulations with a Ti adhesion layer were
also performed, showing a negative effect by increasing to ~17% the minimum reflectivity when SPR is achieved, thus reducing the dynamic range of the signal captured by the system's photodetector. SPR biosensors work by monitoring changes on the refractive index close to the SPR interface, these changes were simulated showing that a change of ~10-4 RIU on the dielectric medium produces a ~0.01°change in the SPR angle. These results will facilitate the physical implementation of label-free biosensing platforms with a CMOS image sensor (CIS) photodetection stage.