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Enhancement of Refractive Index Sensitivity Using Small Footprint S-Shaped Double-Spiral Resonators for Biosensing
Anh Igarashi1, Maho Abe2, Shigeki Kuroiwa3
1Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan.
Sensors (Basel, Switzerland)
|July 14, 2023
Summary
We developed a novel S-shaped double-spiral microresonator (DSR) for highly sensitive detection of liquid and gas analytes. This compact DSR offers a significantly enhanced interface for refractive index biosensing, improving sensitivity and reducing footprint.
Area of Science:
- Photonics
- Microfluidics
- Biosensing
Background:
- Optical ring resonators are used as label-free biosensors, but larger sizes are needed for higher sensitivity, leading to large footprints.
- Existing microring resonators have limited interaction between the evanescent field and analytes, with 99% of the cavity area unused for sensing.
- Scaling up ring resonators for enhanced sensitivity requires significant space and is inefficient in terms of sensing area utilization.
Purpose of the Study:
- To demonstrate a novel S-shaped double-spiral microresonator (DSR) for efficient detection of small volumes of liquid and gas analytes.
- To design a compact and highly sensitive refractive index biosensor with an enhanced contact interface.
- To reduce the overall footprint of microresonator-based sensors while maintaining or improving sensing performance.
Main Methods:
- Fabrication of a silicon-based S-shaped double-spiral resonator on a silicon-on-insulator substrate.
- Characterization of the DSR's optical properties, including quality factors and refractive index sensitivity.
- Testing the DSR for detecting liquid analytes (IPA) in a microfluidic channel and gas analytes (acetone) in a closed environment.
Main Results:
- The DSR achieved a significantly reduced footprint (680 times smaller than microring resonators with similar cavity area).
- High quality factors (1.8 × 10^4) were achieved for 1.2 mm DSR structures, exceeding those of microring resonators.
- A bulk sensitivity of 1410 nm/RIU was demonstrated for detecting IPA solutions, over 10-fold higher than microring resonators.
- Successful detection of 100 ppm acetone gas was achieved using the DSR device.
Conclusions:
- The S-shaped double-spiral microresonator (DSR) offers a compact and highly sensitive platform for microfluidic-based refractive index biosensing.
- The DSR design enhances the interaction interface, leading to superior sensitivity and quality factors compared to traditional microring resonators.
- This novel DSR technology shows great promise for label-free detection of both liquid and gas analytes in small volumes.
