Ball SAW Sensors for Safety and Reliability of Fuel Cell Technologies
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 % among 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.
Seung-Seok Lee, Joon Hyun Lee, Ik Keun Park, Sung-Jin Song, Man Yong Choi
K. Yamanaka "Ball SAW Sensors for Safety and Reliability of Fuel Cell Technologies", Key Engineering Materials, Vols. 321-323, pp. 48-52, 2006