Modeling and simulation of fluid SAW-sensors under acoustic plate mode operation

This paper presents the use of SAW-sensors in the characterization technique for fluid determination. A SAW-sensor model is analyzed with LiNbO₃ substrate using the acoustoelectric effects of the loading fluid on the propagating wave. The changes of the relative velocity and the attenuation of the acoustic wave caused by these effects are used as a characterization criterion for the loading fluid material. In the analysis of this SAW-sensor model, the thickness of the fluid layer is assumed to be infinitely thin but finite. The thickness of the separating air gap between the fluid and the substrate is very small relative to the wavelength. On the other hand, the substrate has a finite thickness. Since operation under acoustic plate mode is assumed, the sensing wave may reflect from the top and the bottom surfaces of the substrate. Computer programs are developed to simulate different fluid behaviors and different types of piezoelectric materials. The simulated obtained results indicate that SAW-sensor can be used as a simple and easy technique to determine the properties of different fluids. They are compared with the published experimental results. Moreover, this sensor can be employed for chemical sensors, biosensors, and pollution applications