Title :
SAW humidity sensor using dielectric hygroscopic polymer film
Author :
Nomura, T. ; Oofuchi, K. ; Yasuda, T. ; Furukawa, S.
fDate :
Oct. 31 1994-Nov. 3 1994
Abstract :
A surface acoustic wave (SAW) sensor for measurement of humidity is described. SAW devices have the ability to directly respond to the inertial mass and elastic mechanical properties of materials in contact with the device surface. Feature enables them to directly sense mass and mechanical properties of their environment. In this paper, we show a new SAW humidity sensor that uses the changes in the film permittivity rather than the mass. A dual SAW delay line fabricated on a piezoelectric substrate was coated with cellulose acetate. For a 128° YX LiNbO3 substrate, the hygroscopic polymer-coating caused a SAW velocity change of 0.33 m/s per 10% relative humidity. The response was linear in the range from 10% to 70% in relative humidity. The results suggest that the SAW humidity sensor using the dielectric interaction with the SAW electric field is quite promising
Keywords :
dielectric thin films; humidity sensors; permittivity; polymer films; surface acoustic wave delay lines; surface acoustic wave sensors; 128° YX cut substrate; LiNbO3; LiNbO3 substrate; SAW electric field; SAW humidity sensor; SAW velocity change; cellulose acetate; dielectric hygroscopic polymer film; dielectric interaction; dual SAW delay line; film permittivity variation; linear response; piezoelectric substrate; surface acoustic wave sensor; Dielectric films; Humidity transducers; Permittivity; Plastic films; Surface acoustic wave delay lines; Surface acoustic wave detectors;
Conference_Titel :
Ultrasonics Symposium, 1994. Proceedings., 1994 IEEE
Conference_Location :
Cannes, France
Print_ISBN :
0-7803-2012-3
DOI :
10.1109/ULTSYM.1994.401638
