2018 Fiscal Year Annual Research Report
Nanojet enhanced fiber sensor with dielectrophoretic concentration for rapid bacteria identification
| Project/Area Number |
18F18351
|
|---|
| Research Institution | The University of Tokyo |
|---|
Principal Investigator |
J・J Delaunay 東京大学, 大学院工学系研究科(工学部), 准教授 (80376516)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TAI YI-HSIN 東京大学, 工学(系)研究科(研究院), 外国人特別研究員
|
|---|
| Project Period (FY) |
2018-11-09 – 2021-03-31
|
| Keywords | label-free detection / optical nanojet |
|---|
| Outline of Annual Research Achievements |
We propose two approaches relying on dielectric materials for label-free biomolecule detection, namely, concentrating light at the tip of an optical fiber and confining light in a guided surface wave. The two approaches use dielectric structures that do not have losses (no metal layer such as in plasmonic structures) but sustain strong light confinement.
Label-free detection is performed by Raman spectroscopy, and so we assembled a micro Raman spectrometer. This setup was used to evaluate the performance of the fabricated optical fiber tips. To fabricate the fiber tips, the fusion splicing technique was used and the obtained tips applied in the detection of organic material layers by Raman spectroscopy. In the current configuration, the probe light was sent through a fiber having a fabricated tip and the Raman signal was detected with a different fiber. Although a Raman signal was observed, it was still too weak to be used for organic material identification (label-free detection).
The multilayer structure sustaining surface waves was studied theoretically and experimentally, and some preliminary results were submitted for publication. Particularly, we showed that the wavelength of the excited surface wave can be controlled in the mid-infrared region, which corresponds to the fingerprint region of most organic materials and thus should enable label-free detection of biomaterials.
|
| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
The ideal shape of the optical fiber tips was obtained by simulation, but could not be fabricated yet. This ideal shape is difficult to obtain and will require a combination of different techniques such as fusion-splicing and etching. So experiments were conducted with other tip shapes such as ball-lens and cone. The micro-Raman spectrometer was built, and Raman spectra from organic layers were measured using the available optical fiber tips. Due to non-optimized fiber tips, the signal-to-noise ratios of these Raman spectra were still too weak to perform identification of organic molecules.
The multilayer structure that sustains surface wave to be used in bio-detection was successfully fabricated and characterized. The bio-detection scheme was not demonstrated yet.
|
| Strategy for Future Research Activity |
To achieve label-free detection of organic molecules, two approaches using optical fiber tips and surface waves will be attempted. We will follow the following steps: fabricate and characterize devices based on 1) the fiber tip with nanojet and 2) the guided surface wave, and 3) test the performance of the fabricated devices in the detection of organic molecules.
1) The fusion splicing technique will be used to fabricate optical fiber tips and the tip shapes will be further refined with a combination of polishing and etching techniques to obtain the ideal shape for the optical fiber tip. Also, an optical setup using fluorescence and/or imaging will be used to characterize the actual dimension and shape of the fiber tips.
2) The structure sustaining guided surface wave will be optimized, fabricated, and tested. The structure will be fabricated using thin film techniques to obtain a stack of dielectric multilayers onto which a slab will be fabricated using lithography and subsequent liftoff. An optical setup enabling spatial filtering (distinguish between light insertion and collection) will be built to characterize the propagation of the guided surface wave.
3) Detection of organic molecules near the optical fiber tips will be performed using Raman spectroscopy. The amplification of the signal by the fabricated fiber tips will be used to characterize the performance of the devices.
|
