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Authors: K. De Vos, I. Bartolozzi, D. Taillaert, W. Bogaerts, P. Bienstman, R. Baets, E. Schacht
Title: Optical biosensor based on silicon-on-insolator microring cavities for specific protein detection
Format: International Conference Presentation
Publication date: 1/2007
Journal/Conference/Book: Proc. of SPIE Photonics West (BiOS)
Volume(Issue): 6447 p.6447DK-1
Location: San Jose, CA, United States
Internal Reference: [N-612]
Download: Download this Publication (366KB) (366KB)

Abstract

Optical label-free biosensors for protein detection attempt to overcome the drawbacks of commercialized systems relying on the detection of labeled biomolecules. We propose an integrated Silicon-on-Insulator optical biosensor based on resonant microring cavities in order to combine fast sample preparation, real time measurements and reduced analyte quantities with a high throughput fabrication method. Deep UV lithography for standard CMOS processing allows for cheap mass fabrication and integration with electronic functions for complete lab-on-chip devices. The SOI material system offers a high refractive index contrast suitable for the fabrication of micron- and submicron sized optical cavities of very high quality. The shift of resonance wavelength that occurs when the dielectric surroundings of such a cavity is changed, can be used for sensing. We demonstrate an SOI optical microring resonator with radius 4 micron capable of detecting bulk refractive index changes of 10-5, well approaching the literature stated limit of detection of 10-6 RIU for biomolecular sensing. Modification of the semiconductor surface, allowing for immobilization of biomolecules, is characterized by X-ray photoelectron spectroscopy, ellipsometry and Atomic Force Microscopy (AFM). As an example of label-free affinity sensing, we use the avidin/biotin system to demonstrate good repeatability and the detection of protein concentrations down to a few ng/ml. Negative control using non-specific binding protein couples proves the realization of real specific binding of the avidin-biotin couple. Further miniaturization will decrease the sensing area, allowing for detection of extremely low analyte concentrations while lining up the microrings in arrays will allow for cheap high throughput label-free multiparameter analyses.

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