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Open AccessArticle

Cascaded-Microrings Biosensors Fabricated on a Polymer Platform

1
School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116023, China
2
Photonics Research Group, Department of Information and Technology, Ghent University, 9000 Ghent, Belgium
3
Information Center, Shandong University, Jinan 250100, China
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(1), 181; https://doi.org/10.3390/s19010181
Received: 10 December 2018 / Revised: 26 December 2018 / Accepted: 2 January 2019 / Published: 6 January 2019
(This article belongs to the Section Biosensors)
Polymer-based single-microring biosensors usually have a small free spectral range (FSR) that hampers the tracing of the spectrum shifting in the measurement. A cascade of two microring resonators based on the Vernier effect, is applied in this article in order to make up for this defect. A small FSR difference between the reference microring and the sensing microring is designed, in order to superpose the periodic envelope signal onto the constituent peaks, which makes it possible to continuously track the spectrum of the sensor. The optical polymer material, Ormocore, which has a large transparent window, is used in the fabrication. The biosensor is fabricated by using an UV-based soft imprint technique, which is considered to be cost-effective and suitable for mass production. By optimizing the volume ratio of Ormocore and the maT thinner, the device can be fabricated almost without a residual layer. The device works at a wavelength of 840 nm, where water absorption loss is much lower than at the infrared wavelengths. A two-step fitting method, including single-peak fitting and whole-envelope fitting, is applied in order to trace the spectral shift accurately. Finally, the two-cascaded-microrings biosensor is characterized, and the obtained FSR is 4.6 nm, which is 16 times larger than the FSR of the single microring biosensor demonstrated in our previous work. Moreover, the sensitivity can also be amplified by 16-fold, thanks to the Vernier effect. View Full-Text
Keywords: microring biosensor; polymer waveguide; Vernier effect; nanoimprint microring biosensor; polymer waveguide; Vernier effect; nanoimprint
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Liang, Y.; Liu, Q.; Wu, Z.; Morthier, G.; Zhao, M. Cascaded-Microrings Biosensors Fabricated on a Polymer Platform. Sensors 2019, 19, 181.

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