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Ultrasonic-assisted point-one-shot mid-infrared Fourier spectroscopy for realization of ear-clip type non-invasive blood glucose sensors: ultrasonic-assisted method for production of a reflection plane near the skin surface and detection of the blood glucose absorption peak in mice (2nd report)
Author(s): Natsumi Kawashima; Ichiro Ishimaru; Tomoya Kitazaki; Kosuke Nogo; Hanyue Kang; Akira Nishiyama; Kenji Wada
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Paper Abstract

For monitoring and prevention of lifestyle diseases, we have investigated development of non-invasive ear-clip type blood glucose sensors that can be used by individuals in daily life. Because mid-infrared light (λ = 8–14 μm) is absorbed strongly by water, it is difficult to detect transmitted light from human bodies. We propose that an ultrasonic-assisted method, which can actively produce a reflection plane at a blood vessel (depth of around 100 μm), could be used to detect internal reflected light from biological tissues. An ultrasonic standing wave produced near the skin surface by an ultrasonic vibrator can form refractive index boundaries between areas of high and low density. Additionally, we can use a low ultrasonic frequency (1 MHz) that does not suffer from heavy damping by parametric standing waves, which appear in non-rigid samples and produce reflection planes at the same depth when using a high frequency (10 MHz). At the refractive index boundary nearest the skin surface, the light from inside biological tissues is reflected and can be used to obtain information of biological components. The optical path length can be set by changing the measurement depth by altering the ultrasonication frequency. We measured internal reflected light from the ears of mice (blood glucose level = 120 mg/dL) non-invasively using our unique mid-infrared spectroscopic imager and obtained absorption peaks for blood glucose (λ = 9.3 μm and 9.7 μm). Mid-infrared spectroscopy can be applied to measurements in samples with high water contents.

Paper Details

Date Published: 20 February 2019
PDF: 4 pages
Proc. SPIE 10885, Optical Diagnostics and Sensing XIX: Toward Point-of-Care Diagnostics, 108850V (20 February 2019); doi: 10.1117/12.2509124
Show Author Affiliations
Natsumi Kawashima, Kagawa Univ. (Japan)
Ichiro Ishimaru, Kagawa Univ. (Japan)
Tomoya Kitazaki, Kagawa Univ. (Japan)
Kosuke Nogo, Kagawa Univ. (Japan)
Hanyue Kang, Kagawa Univ. (Japan)
Akira Nishiyama, Kagawa Univ. (Japan)
Kenji Wada, Kagawa Univ. (Japan)

Published in SPIE Proceedings Vol. 10885:
Optical Diagnostics and Sensing XIX: Toward Point-of-Care Diagnostics
Gerard L. Coté, Editor(s)

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