Silicon-on-Insulator microring resonator for sensitive and label-free biosensing

TLDR

Label‑free biosensors aim to avoid the stability and reliability issues of labeled‑molecule detection. The study proposes a sub‑100‑µm² SOI microring resonator as a label‑free biosensor. The device senses by monitoring resonance wavelength shifts of SOI microring cavities fabricated with Deep UV lithography, and its performance is validated using the avidin/biotin binding assay. The microring achieves a theoretical mass sensitivity of 1 fg and detects protein concentrations as low as 10 ng/mL, outperforming bulk refractive index sensitivity.

Abstract

Label-free biosensors attempt to overcome the stability and reliability problems of biosensors relying on the detection of labeled molecules. We propose a label-free biosensor based on microring cavities in Silicon-on-Insulator (SOI) that fits in an area below 10x10mum(2). The resonance wavelength shift that occurs when the surroundings of a cavity is changed, is used for sensing. While theoretically the performance for bulk refractive index changes is moderate (10(-5)), this device performs outstanding in terms of absolute molecular mass sensing (theoretical sensitivity of 1fg molecular mass) thanks to its extremely small dimensions. We use the avidin/biotin high affinity couple to demonstrate good repeatability and detection of protein concentrations down to 10ng/ml. Fabrication with Deep UV lithography allows for cheap mass production and integration with electronic functions for complete lab-on-chip devices.