A surface acoustic wave (SAW), device composed of polymer and ceramic fillers, exhibiting high piezoelectricity and flexibility, has a wide range of sensing applications in the aerospace field. The demand for flexible SAW sensors has been gradually increasing due to their small size, wireless capability, low fabrication cost, and fast response time. This paper discusses the structural, thermal, and electrical properties of the developed sensor, based on different micro- and nano-fillers, such as lead zirconate titanate (PZT), calcium copper titanate (CCTO), and carbon nanotubes (CNTs), along with polyvinylidene fluoride (PVDF) as a polymer matrix. The piezocomposite substrate of the SAW sensor is fabricated using a hot press, while interdigital transducers (IDTs) are deposited through 3D printing. The piezoelectric properties are also enhanced using a non-contact corona poling technique under a high electric field to align the dipoles. Results show that the developed passive strain sensor can measure mechanical strains by examining the frequency shifts of the detected wave signals.
The demand for acoustic wave-based devices has been rapidly increasing in the aerospace, chemical, and biological fields due to their versatility towards sensing measurands. This paper explores the characteristics and effectiveness of acoustic wave-based two-port sensors designed with bidirectional IDT electrodes placed in different configurations, such as surface mounted or embedded inside the substrate, through numerical and experimental analysis. The numerical study involves 3D modeling of the sensor design to investigate wave characteristics by utilizing time-domain, i.e., time delay and wave patterns, and frequency-domain analysis, i.e., scattering parameter study. The sensor made of polyvinylidene fluoride polymer is modeled to ensure the concordance between the theoretical and numerical results as well as a preliminary experimental result obtained from transparent piezoelectric films. The coupling of modes theoretical model is used to obtain the device’s frequency response by a transmission matrix cascading technique. These investigated results will stand as guidance and facilitate defining an approach that can predict the behavior of the sensor with a specific design under different operating environments and expand its viability towards multi-functional devices that are reliable and sensitive to intended measurands.
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