SAW humidity sensor using dielectric hygroscopic polymer film

Author

Nomura, T. ; Oofuchi, K. ; Yasuda, T. ; Furukawa, S.

Volume

1

fYear

1994

fDate

Oct. 31 1994-Nov. 3 1994

Firstpage

503

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;

fLanguage

English

Publisher

ieee

Conference_Titel

Ultrasonics Symposium, 1994. Proceedings., 1994 IEEE

Conference_Location

Cannes, France

Print_ISBN

0-7803-2012-3

Type

conf

DOI

10.1109/ULTSYM.1994.401638

Filename

401638