A unified model of SH waves in a layered piezoelectric semi-region concerning nonlocal effects and its utilization in optimizing the performance of SH-SAW nanoactuators

To modulate the nanoscale particle at the structures’ surface, the waves’ energy should be limited to the structure's surface. That requires us to slow down the waves’ velocity by the nonlocal effect. This paper uses the nonlocal differential model to overall derive the phase velocity equation of Shear Horizontal (SH) waves in a layered piezoelectric half-domain. At first, we aim to testify the current theoretical model. Thus, we obtain the dispersive curves given by the current model and the finite element method. The results show good consistency with each other while the wavenumber (frequency) is neither awfully small nor considerable. The empirical formulas for the criteria of the existence of the wave, penetration depth, and electromechanical coupling factor are proposed. Based on the empirical formula, it proves that a great value of the half-layer's nonlocal constants, l₃, to the piezoelectric film's nonlocal constants, l₁, impedes the usage of Surface Acoustic Wave (SAW) nanoactuator. We apply FEM technique to conclude that selecting the first mode of SH waves and imposing the shorted case at the upper surface of the piezoelectric layer is feasible for localizing the mechanical signal on the piezostructures' uppermost surface. Based on the derivation of penetration depth, increasing wavenumbers or selecting a piezomaterial owning a greater nonlocal constant contribute to localizing the waves’ energy at the surface. In addition, the EMC factor benefits notably from a greater nonlocal constants or working frequencies. However, an insurmountable EMC factorK_max²exists when the waves’ frequency is exceedingly colossal, being irrelevant to nonlocal effects and barely relying on the physical attributes of piezoelectric material. The piezoelectric material with a higher k₁₅² gives rise to a greater K_max². Lastly, to assess the correctness of the work analyzed by the nonlocal differential model, nonlocal integral model is applied to execute a study of the dispersion behavior of the fundamental mode wave. It is found that the waves’ velocity corresponding to the electric open case (c_o) is the same as that corresponding to the electric short case (c_s) at high frequencies. The dispersive properties evaluated by the nonlocal differential model cause that c_o is more considerable than c_s at high frequencies. Since the results calculated by the nonlocal differential model are more physically persuasive, they further substantiates the present work. The outcome offers an avenue to revolutionize the fabrication of SAW nanoactuators, being feasible for sorting and separating nanoscale particles.