Ultramultiple roundtrips of surface acoustic wave on sphere realizing innovation of gas sensors

A thin beam of wave usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is naturally collimated, realizing ultramultiple roundtrips along an equator of the sphe...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2006-04, Vol.53 (4), p.793-801
Main Authors: Yamanaka, K., Ishikawa, S., Nakaso, N., Takeda, N., Dong Youn Sim, Mihara, T., Mizukami, A., Satoh, I., Akao, S., Tsukahara, Y.
Format: Article
Language:English
Subjects:
Acoustic beams
Acoustic diffraction
Acoustic sensors
Acoustic waves
Apertures
Attenuation
Beams (radiation)
Collimators
Diffraction
Ferroelectric materials
Focusing
Gas detectors
Gas sensors
Surface acoustic wave devices
Surface acoustic waves
Technological innovation
Thin films
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Summary:A thin beam of wave usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is naturally collimated, realizing ultramultiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high-performance ball SAW sensors. The advantage of ball SAW is most fully appreciated when applied to a very thin sensitive film for which the multiple-roundtrip enhances the sensitivity, but the attenuation loss is not very large. It is exemplified in a hydrogen gas sensor that realizes a wide sensing range of 10 ppm to 100% for the first time, and realizes relatively fast response time of 20 s without heating the sensitive film.
ISSN:0885-3010
1525-8955
0885-3010
DOI:10.1109/TUFFC.2006.1621507