Thin film flexible/bendable acoustic wave devices: Evolution, hybridization and decoupling of multiple acoustic wave modes

Abstract

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

“…On the contrary, if the ratio is smaller than one, Lamb waves are dominant, while hybrid modes (both Rayleigh and Lamb waves) are commonly observed for a ratio near one. 22 The FEA simulation results for wave vibration patterns on different Al sheets show that when the Al sheet thickness (i.e., 600 and 1500 μm) is larger than the device wavelength, the SAW devices generate a Rayleigh mode and a Sezawa mode, as depicted in Figure 2 c,d. When the Al sheet thickness is in a similar range to the device wavelength, the A 0 mode and pseudo-Rayleigh mode are hybridized together at a frequency of 13.72 MHz, and the pseudo-S 0 mode and the Sezawa mode are also obtained, as illustrated in Figure 2 e. When the Al sheet thickness is further decreased to 50 μm, the wave vibration modes are changed into the typical Lamb waves, without Rayleigh and Sezawa modes observed, as shown in Figure 2 f. The simulated wave modes for SAW devices with the wavelengths of 64 μm and 200 μm and Al sheet thicknesses from 50 to 1500 μm are shown in Figure S5 in the Supporting Information .…”

“… 30 This is mainly due to their poor stiffness, which causes a large deformation at a high RF power, thereby causing significant dissipation of acoustic energy into the substrate. Another major factor is the change of wave modes as the Rayleigh waves change into Lamb waves, 22 which is less efficient than Rayleigh waves for fluidic actuation. 31 Conversely, thick Al sheets (e.g., >1 mm) do not easily deform.…”

Acoustofluidics along inclined surfaces based on AlN/Si Rayleigh surface acoustic waves

“…SAW technologies based on piezoelectric thin films such as ZnO and AlN present several distinct advantages over bulk substrates, including flexible electrode designs, high breakdown voltage and easily integrated with other electronics [4,23]. Another key advantage using piezoelectric thin films is that they can be easily deposited onto different substrates such as silicon, glass, metal and polymer with new functions, and then different acoustic velocities or wave modes can be obtained [24][25][26][27]. Therefore, thin film SAW techniques have been considered as one of the key directions for acoustofluidics and lab-on-a-chip applications.…”

Quantum information memory based on reconfigurable topological insulators by piezotronic effect

“…Strain-induced piezopotential can effectively tune the carrier generation, transportation and recombination inside the material [3,4]. Inspired by ultra-high performance, a variety of piezotronic and piezo-phototronic devices have been developed such as, nanogenerator [5,6], piezoelectric field effect transistors [7], flexible spintronic devices [8], acoustic wave devices [9,10], photon detectors [11], solar cells [12,13] and LEDs (light emitting diodes) [14]. Additionally, utilizing the piezoelectric effect to adjust the quantum states has been proposed for a series of piezotronic devices such as piezotronic strain-gated logic devices [15] and quantum photovoltaic devices [16].…”