Flexural plate-wave sensor: chemical vapor sensing and electrostrictive excitation

The authors describe the use of flexural plate waves traveling in thin composite plats of silicon nitride, zinc oxide, and aluminum for gravimetric chemical vapor sensing. Experiments with sorptive films of poly(dimethylsiloxane) and ethyl cellulose exposed to vapors of toluene, 1,1,1,-trichloroethane, and carbon-tetrachloride showed the high sensitivity of the plate sensor. Detection in the parts-per-billion range is achievable. The authors also demonstrate the use of electrostriction to generate flexural plate waves; optical-and capacitive-plate wave detection schemes are also described. Advantages of the electrostrictive structure include ease of fabrication and the possibility of achieving higher mass sensitivities, especially when operating the sensor in liquids