Bending behaviors of flexible acoustic wave devices under non-uniform elasto-plastic deformation

Abstract

Flexible acoustic wave devices (FAWDs) have been explored for various applications where bending is inevitable. However, theoretical investigations of bending behavior of FAWDs hitherto are mostly done in the linear deformation regime. Herein, we develop a multi-sublayer model based on a stiffness matrix method for analysis of frequency shifts of surface acoustic wave (SAW) and Lamb waves under elasto-plastic deformations. Using this model, we calculate the frequency shifts for the cases of both an elastic bending and an elasto-plastic bending. Experimental frequency shifts of ZnO/Al flexible devices show good agreements with the theoretical results in the elastic bending tests (with a relative error of strain sensitivity < 3%), and also show relatively good agreements with the qualitative theoretical predictions in the nonlinearly elasto-plastic bending tests. For three successive bending and recovery processes, the experimentally obtained frequency shifts show good repeatability in the elastic and elasto-plastic bending stages, demonstrating maximum relative errors of strain sensitivities less than 6.1% and 18.2%.

Flexible/Bendable Acoustofluidics Based on Thin-Film Surface Acoustic Waves on Thin Aluminum Sheets

“…When the SAW device is bent, all the densities and elastic constants of ZnO and Al as well as the device wavelengths will change. The total frequency shifts can be regarded as the sum of several frequency shift components caused by the changes of the density, elastic constant, device wavelength, and the stress, respectively …”

“…The total frequency shifts can be regarded as the sum of several frequency shift components caused by the changes of the density, elastic constant, device wavelength, and the stress, respectively. 39 Figure 3a shows the calculated frequency shifts (A 0 mode) due to the changes of density, elastic constant, and device's wavelength as a function of bending strains. The frequency shift caused by the density change is relatively small (<1 kHz under strain levels of 3000 με), while the change in the elastic constant has a larger impact than that of the wavelength, leading to an apparent nonlinear effect with the increase of strain.…”

Recent Progress in Polymeric Flexible Surface Acoustic Wave Devices: Materials, Processing, and Applications

“…However, as previously mentioned, the deposition of piezoelectric crystalline films on polymeric substrates is a challenging process due to the significant differences in mechanical and thermal properties between the two layers. As an alternative, thin metallic foils such as aluminum [ 14,134,135 ] have emerged as an interesting option for flexible SAW device fabrication offering easy processability thanks to the high thermal resistance, but they also have limitations. For instance, metallic foils have higher costs compared to polymers, low impedance, and are often opaque, limiting their use in applications where transparency is important.…”

Multifunctional and Wearable Patches Based on Flexible Piezoelectric Acoustics for Integrated Sensing, Localization, and Underwater Communication

“…The deformation of flexible devices is generally accompanied by variations of film's internal stress and mechanical properties, which may result in the degradation of the transceiver performance. [36] Therefore, the proposed acoustic communication scheme was further evaluated under several bending conditions.…”