Development of a high-sensitivity strain measurement system based on a SH SAW sensor

Abstract

A strain measurement system based on a shear horizontal surface acoustic wave (SH SAW) was developed. The developed system is composed of a SAW microsensor, a printed circuit board (PCB), an adhesive and a strain gauge. When a compression force is applied to the PCB by the strain gauge, the PCB is bent so that external strain energy can be evenly delivered to the microsensor without any detachment of the sensor from the board. When a stretching force is applied to the PCB under the condition that one side of the PCB is fixed and the other side is modulated, the actual length of the SAW delay line between the two interdigital transducers (IDTs) is increased. The increase in the delay line length causes a change in the time for the propagating SAW to reach the output IDT. If strain energy is applied to the piezoelectric substrate, the substrate density is changed, which then changes the propagation velocity of the SAW. Coupling-of-modes modeling was conducted prior to fabrication to determine the optimal device parameters. Depending on the strain, the frequency difference was linearly modulated. The obtained sensitivity for stretching was 17.3 kHz/% for the SH wave mode and split electrode. And the obtained sensitivity for bending was 46.1 kHz/% for the SH wave mode and split electrode. The SH wave showed about 15% higher sensitivity than the Rayleigh wave, and the dog-bone PCB showed about 8% higher sensitivity than the rectangular PCB. The obtained sensitivity was about five times higher than that of existing SAW-based strain sensors.

Surface Acoustic Wave (SAW) Sensors: Physics, Materials, and Applications

“…Rayleigh waves are the modal superposition of longitudinal (P) and shear vertical (SV) wave components with traction-free boundary conditions on the substrate [ 24 ]. Due to the property of this wave, the surface particles move in an elliptical fashion, normal to the surface and parallel to the direction of the propagation [ 90 , 91 ]. In this type of wave, the velocity of the wave is solely dependent on the material of the substrate and the orientation of the crystals.…”

“…Please refer to Section 3.2 for an understanding of crystal-cut SAW wave propagation. A SAW sensor based on SH waves can be used for liquid and gas sensing [ 90 ]. Figure 4 shows the schematic of the shear horizontal waves.…”

Three-Dimensional Finite Element Analysis and Characterization of Quasi-Surface Acoustic Wave Resonators

“…Both 2D and 3D FEA simulations are conducted in COMSOL Multiphysics (COMSOL Multiphysics 5.4, COMSOL AB, Stockholm, Sweden), in order to compare their differences. The QSAW resonators are designed with four different wavelengths, , of 10.4 m, 10 m, 9.6 m and 9.2 m. In this work, split IDT design, rather than typical IDT structure, is adopted to reduce the insertion loss and improve the frequency stability [ 19 ]. The split IDT is composed of a grating structure with interval of /8 and a center-to-center distance of /4.…”

Frequency-based detection of female Aedes mosquito using surface acoustic wave technology: Early prevention of dengue fever

“…However, device performance and sensitivity are dramatically affected by the thickness and properties of each layer in the structure of layered SAW devices [23]. A 128º YX cut LiNbO 3 substrate was selected for the female Aedes mosquito sensors because of its high SAW velocity (3996 m/s) and large electromechanical coupling coefficient (5.5%) [24]. A 1.5 m thick Zinc oxide (ZnO) layer is deposited on the substrate to maximize the SAW device coupling coefficient [25,26].…”