Thin-film piezoelectric acoustic sensor (TFPAS): further experimental validation of the theory of resonance sensitivity

The theory developed earlier, predicts that TFPAS sensitivity exhibits a periodic character, the period being equal to one half of the longitudinal acoustical wavelength in the sorption film material, λr. Sensitivity maxima occur at lr = (2n − 1)λr/4, where n is 1, 2, 3, … and lr is the sorption film thickness. Preliminary experiments showed that there was indeed a sharp increase in the sensitivity of TFPAS in the vicinity of λ/4 resonance. In this paper, λ/4 resonance is confirmed and the theory is further experimentally validated by observing another resonance at 3λ/4. Potential applications of TFPAS operated at resonance frequencies for real-time detection and identification of chemical and biological weapons are discussed.