Characterization of SION microring resonators for biosensing applications

In this paper, we presented a study on microring-based photonic biosensors. The analyte was Aflatoxin M1, which is known to be hepatotoxic and carcinogenic. We measured the bulk Sensitivity (S) and Limit of Detection (LOD) as a function of the waveguide composition and dimensions. The sensing device was based on an array of four SiON microring resonators, fiber-coupled to a VCSEL (wavelength 850 nm), a silicon photodetector and packaged into a microfluidic platform. Characterization of volumetric sensing was performed on ring resonators with lOOum radius and core refractive index n_SiON=1.66. For this purpose, glucose-water solutions at various concentrations were flown over the sensors. The highest sensitivity, measured on these samples, exceeded 80 nm/RIU. To characterize the limit of detection of the sensors, we also measured the uncertainty of our experimental readout system, obtaining LOD as low as 3×10 ^-6 RIU. Finally, few functionalized sensors were used to detect solutions of various concentrations of Aflatoxin M1 in buffer, with successful detection down to ~0.51 ng/ml. The functionalization was based on a wet silanization and specific DNA-aptamer binding on the chip. The reproducibility and reusability of the sensor was also investigated by using glycine solution. This work was supported by the FP7 EU project "Symphony" (Grant agreement no: 610580).