Type of Publication
Year of Publication

K. Yamanaka

ISBN Number

1013-9826 0-87849-412-x


Detection of hydrogen gas is a crucial task for establishing safety and reliability of fuel cells, a key technology for the environment and our society. However, hydrogen is difficult to detect and various hydrogen sensors have many drawbacks. Here we report a novel hydrogen gas sensor, the ball surface acoustic wave (SAW) sensor, using Pd or PdNi sensitive film. The ball SAW sensor is based on a novel phenomenon, diffraction-free propagation of collimated beam along an equator of sphere. The resultant ultra-multiple roundtrips of SAW makes it possible to achieve highest sensitivity among SAW sensors. Moreover, it enables to use a very thin sensitive film, and consequently the shortest response time (2s) was realized. In terms of the sensing range, it has the widest range of 10 ppm to 100 %2among any hydrogen sensors including FET or resistivity sensors. The ball SAW sensor can be applied not only to hydrogen but also to any gasses and possibly to liquids.




Times Cited: 1 1st International Conference on Advanced Nondestructive Evaluation Nov 07-09, 2005 Jeki Isl, SOUTH KOREA 1