Table 1.

Table describing types of waves and materials to be used.

Wave Type	Materials	Applicable Frequency Range	Attenuat ion	Misc. Comments
Rayleigh Wave	128° YX lithium niobate 41° YX lithium niobate ST-Quartz	~3 MHz–~2 GHz Most application 345 MHz	Highly attenuative With fluid load on the top of the substrate, attenuation is significant	For Rayleigh wave generation, power consumption is lower Can be of low cost
Lamb Wave	Generated in any bounded plate-like structure. This wave is generated in layered media at lower frequencies. However, for high frequency applications, it is hard to find natural material where Lamb wave could be used for SAW sensors. Thus, artificial thin films—e.g., ZnO, AlN, PVDF thin film—could be used	~200–~2 MHz in natural materials 200 MHz–2 GHz in artificially made thin films	Low attenuation, propagates long distance In presence of liquid load on the substrate, leaky-Lamb wave propagates Leaky waves attenuate faster	Lamb waves consists of Antisymmetric and Symmetric wave modes. First antisymmetric (${\mathit{A}}_0$) and first symmetric (${\mathit{S}}_0$) wave modes are easy to detect with appropriate delay lines.
SH-Wave	64° YX lithium niobate 36° YX lithium niobate Quartz	~100–~450 MHz	Nondispersive Low attenuation; however, sometimes combined with bulk wave, so hard to detect	Low cost Wide application, Suitable to use with fluid loading on the substrate
Love Wave	Must have a guiding layer on top of the substrate Possible substrates: Similar to SH-wave Possible guiding layers: SiO2, ZnO, TiO2, SU-8 photoresists, polymethyl methacrylate etc.	~100–~450 MHz same as SH wave	With increasing coating thickness insertion loss increases Attenuation in guiding layer or the coating layer affects significantly	Highly sensitive Works in fluid loading environment