Search Results (194)

This article investigates the use of bent metal strips on the top of a SiO₂ layer for the suppression of spurious modes in temperature-compensated surface acoustic wave (TC-SAW) resonators employing a SiO₂/Cu/128°YX-LiNbO₃ structure. The proposed metal strip method includes two parts: a primary metal strip located at the edge of the interdigital transducer (IDT) aperture region and a secondary metal strip in the gap region. The impact of the geometric parameters of bent metal strips was calculated by the 3D finite element method (FEM), and theoretical simulation results show that this method can effectively suppress the transverse modes and mitigate the gap modes originating from the gap region in conventional TC-SAW resonators. Furthermore, experimental validation further confirms that the proposed method can effectively suppress nearly all spurious modes without degrading the performance of the quality factor. Full article

This paper presents a study on the propagation of acoustic waves in gallium nitride (GaN) layers deposited on sapphire substrate. The influence of GaN layer thickness and the configuration of interdigital transducers (IDTs) on the generation and propagation of different surface wave modes, including Rayleigh, Sezawa, and Love waves, was analyzed. Experimental measurements in the 100 MHz–6 GHz range were complemented by numerical simulations using the finite element method (FEM). The results demonstrated a strong dependence of wave characteristics on technological parameters, particularly the quality of the GaN–sapphire interface. The data obtained can be utilized for optimizing the design of acoustic sensors, resonators, and RF filters. Full article

This paper presents a thermal gas flow sensing system, from surface acoustic wave (SAW) temperature sensor to oscillation circuit and multi-module miniaturization integration. A single-port GaN/Si SAW resonator with single resonant mode and excellent characteristics was fabricated. Combined with an in-house-developed SiGe HBT, a temperature-sensitive high-frequency oscillator was constructed. Under constant temperature control, system-level flow measurement was achieved through dual-oscillation configuration and modular integration. The fabricated SAW device shows a temperature coefficient of frequency (TCF) −28.29 ppm/K and temperature linearity 0.998. The oscillator operates at 1.91 GHz with phase noise of −97.72/−118.62 dBc/Hz at 10/100 kHz offsets. The system demonstrates excellent dynamic response and repeatability, directly measuring 0–50 sccm flows. For higher flows (>50 sccm), a shunt technique extends the test range based on the 0–10 sccm linear region, where response time is <1 s with error <0.9%. Non-contact operation ensures high stability and long lifespan. The sensor shows outstanding performance and broad application prospects in flow measurement. Full article

Resonant acoustic technology utilizes low-frequency vertical harmonic vibrations to induce full-field mixing effects in processed materials, and it is regarded as a “disruptive technology in the field of energetic materials”. Although numerous scholars have investigated the mechanisms of resonant acoustic mixing, there remains a lack of parameter selection methods for improving product quality and production efficiency in engineering practice. To address this issue, this study employs phase-field modeling and fluid–structure coupling methods to numerically simulate the transport process of glycerol during resonant acoustic mixing. The research reveals the mass transfer mechanism within the flow field, establishes a liquid-phase distribution index for quantitatively characterizing mixing effectiveness, and clarifies the enhancement effect of fluid transport on solid particle mixing through particle tracking methods. Furthermore, parameter studies on vibration frequency and amplitude were conducted, yielding a critical curve for guiding parameter selection in engineering applications. The results demonstrate that Faraday instability first occurs at the fluid surface, generating Faraday waves that drive large-scale vortices for global mass transfer, followed by localized mixing through small-scale vortices. The transport process of glycerol during resonant acoustic mixing comprises three distinct stages: stable Faraday wave oscillation, rapid mass transfer during flow field destabilization, and localized mixing upon stabilization. Additionally, increasing either vibration frequency or amplitude effectively enhances both the rate and effectiveness of mass transfer. These findings offer theoretical guidance for optimizing process parameters in resonant acoustic mixing applications. Full article

Alloying AlN with ScN provides a robust strategy for engineering its intrinsic bandgap, phonons and dielectric functions, and ScAlN alloys have demonstrated great promise in applications including the 5G mobile network, surface acoustic wave devices and nanophotonics. Sc doping has been shown to greatly influence the phonons and infrared dielectric functions of AlN, yet few studies have focused on its influence on surface phonon polaritons, which are crucial to modulating the radiative properties of ScAlN metasurfaces. Herein, we combined first-principles and finite element method (FEM) simulations to fully investigate the effects of Sc incorporation on the phonon dispersion relation, propagation and localization of SPhPs and the modulated radiative properties of ScAlN nanoresonators. As the Sc doping concentration increases, the highest optical phonon frequencies are reduced and are largely directly related to enlarged lattice parameters. Consequently, the coupling strength among incident photons and phonons decreases, which leads to a reduced absorption peak in the infrared dielectric functions. Moreover, the propagation length of the SPhPs in ScAlN is largely reduced, and localized resonance modes gradually disappear at a higher Sc doping concentration. This work provides physical insights into the spectra tuning mechanisms of ScAlN nanoresonators via Sc doping and facilitates their applications in nanophotonic devices. Full article

Love wave surface acoustic wave (LSAW) sensors are crystal resonators known for their high potential for biosensing applications due to their high sensitivity, real-time detection, and compatibility with microfluidic systems. Commercial LSAW devices are costly, and manufacturing them is even more expensive, making accessibility a significant challenge. Additionally, their use requires specialized systems, and with only a few manufacturers dominating the market, most available solutions are proprietary, limiting customization and adaptability for specific research needs. In this work, a low-cost open-source LSAW biosensing system prototype was developed based on a commercially acquired resonator. The development integrates microfluidics through a polydimethylsiloxane (PDMS) chip, low-cost electronics, and both 3D printed ultraviolet (UV) resin and polylactic acid (PLA) parts. The instrument used for measurements was a vector network analyzer (VNA) that features open-source software. The code was customized for this study to enable real-time, label-free biosensing. Experimental validation consisted of evaluating the sensitivity and repeatability of the system, from the setup to its use with different fluids. Results demonstrated that the development is able to advance to more complex applications. Full article

The resonant frequency of an SAW oscillator can be modulated by varying the signal amplitude, due to non-linear acoustic interactions within the chemoselective layer. In this study, we developed an explicit model to describe the amplitude–frequency behavior of a tunable SAW oscillator. A polymeric layer of variable thickness was deposited in a circular area (radius 1.1 mm) at the center of the piezoactive surface. Increasing the oscillator loop attenuation resulted in a continuous increase in the resonant frequency by up to 1.8 MHz. The layer was modeled as a succession of non-interacting sub-layers of varying thicknesses. As a result, the function model consists of a superposition of terms, each corresponding to a layer region of distinct length and thickness. The maximum difference between the experimental data and function model (also known as residual of the fit) was below 1% (13.02 kHz) of the resonant frequency variation, thus supporting the validity of our approach. While our model proved successful, the results suggest that some interactions are unaccounted for, as evidenced by the periodicity of the residuals of fit and unrealistically large variation in acoustic wave velocity. Full article

In the context of autonomous environmental monitoring, this study investigates a surface acoustic wave (SAW) sensor designed for selective carbon dioxide (CO₂) detection. The sensor is based on a LiTaO₃ piezoelectric substrate with copper interdigital transducers and a polyetherimide (PEI) layer, chosen for its high electromechanical coupling and strong CO₂ affinity. Finite element simulations were conducted to analyze the resonance frequency response under varying gas concentrations, film thicknesses, pressures, and temperatures. Results demonstrate a linear and sensitive frequency shift, with detection capability starting from 10 ppm. The sensor’s autonomy is ensured by a piezoelectric energy harvester composed of a cantilever beam structure with an attached seismic mass, where mechanical vibrations induce stress in a piezoelectric layer (PZT-5H or PVDF), generating electrical energy via the direct piezoelectric effect. Analytical and numerical analyses were performed to evaluate the influence of excitation frequency, material properties, and optimal load on power output. This integrated configuration offers a compact and energy-independent solution for real-time CO₂ monitoring in low-power or inaccessible environments. Full article

This article presents an investigation into the use of nanoscale phononic crystals (PnCs) as reflectors for surface acoustic wave (SAW) resonators, with a focus on pillar-based PnCs. Finite element analysis was employed to simulate the phononic dispersion characteristics and to study the effects of the pillar shape, material and geometric dimensions on achievable acoustic bandgap. To validate our concept, we fabricated SAW resonators and filters incorporating the proposed pillar-based PnC reflectors. The PnC-based reflector shows promising performance, even with smaller number of PnC arrays. In this regard, with a PnC array reflector consisting of 20 lattice periods, the SAW resonator exhibits a maximum bode-Q of about 1600, which can be considered to be a reasonably high value for SAW resonators on bulk 42° Y-X lithium tantalate (42° Y-X LiTaO₃) substrate. Furthermore, we implemented SAW filters using pillar-based PnC reflectors, resulting in a minimum insertion loss of less than 3 dB and out-of-band attenuation exceeding 35 dB. The authors believe that there is still a long way to go in making it fit for mass production, especially due to issues related with the accuracy of fabrication. But, upon its successful implementation, this approach of using PnCs as SAW reflectors could lead to reducing the foot-print of SAW devices, particularly for SAW-based sensors and filters. Full article

Although shear horizontal waves have advantages over longitudinal waves, including a higher resolution, less wave mode conversion, and much better reflection coefficients at void and crack interfaces in nondestructive detection, they require good contact surface flatness and efficient coupling agents. In this paper, we analyze and design the basic components of the dry-coupled ultrasonic shear wave probe through theoretical analyses and numerical simulations. The admittance characteristics, resonant frequency, and electromechanical coupling coefficients of the double-laminated vibrator under different size parameters in both 2D and 3D models are simulated, and the probe structures are optimized based on the simulation results and operational requirements. The simulation results of the wave field excited by the double-laminated vibrator show the effectiveness of the optimized probe models. Additionally, the dry coupling method of the probe is simulated to study the acoustic energy distribution under various dry-coupled structures. Finally, we compare the measured admittance with the simulated values, and they are in good agreement. Full article

Sorting particles or cells of specific sizes in complex systems has long been a focus of many researchers. Acoustic surface waves, which generate acoustic radiation forces on particles or cells and, thus, influence their motion, are commonly used for the non-destructive separation of particles or cells of specific sizes. In previous studies, the frequency of acoustic surface wave generation has been limited by the interdigitated transducer (IDT). To extend the effective operating frequency range of the IDT, a slanted-finger interdigitated transducer (SFIT) with a wide acoustic path and multiple operating frequencies was designed. Compared with traditional acoustic sorting devices, which suffer from a limited frequency range and narrow acoustic paths, this new design greatly expands both the operating frequency range and acoustic path width, and enables adjustable operating frequencies, providing a solution for sorting particles or cells with uneven sizes in complex environments. The optimal resonance frequency is distributed within the 32–42 MHz range, and the operating frequencies within this range can generate a standing wave acoustic path of approximately 200 $\mathsf{\mu }$m, thus enhancing the effectiveness of the operating frequencies. The microfluidic sorting device based on SFIT can efficiently and accurately sort polystyrene (PS) with particle sizes of 20 $\mathsf{\mu }$m, 30 $\mathsf{\mu }$m, and 50 $\mathsf{\mu }$m from mixed PS microspheres (5, 10, 20 $\mathsf{\mu }$m), (5, 10, 30 $\mathsf{\mu }$m), and (5, 10, 50 $\mathsf{\mu }$m), with a sorting efficiency and purity exceeding 96%. Additionally, the device is capable of sorting other types of mixed microspheres (5, 10, 20, 30, 50 $\mathsf{\mu }$m). This new wide-acoustic-path, multi-frequency sorting device demonstrates the ability to sort particlesin a high-purity, label-free manner, offering a more alternative to traditional sorting methods. Full article

Microplastics (MPs) and nanoplastics (NPs), which are widespread in many habitats as the byproducts of various industrial processes, pose considerable environmental and health hazards. However, current, conventional methods for detecting and characterizing them are considerably lacking in throughput, sensitivity, reliability, and field deployability. In the current report, we review the state of the art in biosensor-based MP/NP detection, in particular, describing advances in optical and electrochemical approaches, along with the development of novel biorecognition elements and the application of bioinformatics tools. Full article

With the rapid development of fifth-generation (5G) mobile communication technology, the performance requirements for radio frequency front-end surface acoustic wave (SAW) devices have become increasingly stringent. Surface acoustic wave devices on piezoelectric thin film-based layered structures with high electromechanical coupling coefficients and low-frequency temperature compensation characteristics have emerged as a key solution. In this work, a SAW resonator based on an Al/41° Y-X LiNbO₃/SiO₂/poly-Si/Si multi-layered structure is proposed. FEM modeling of the proposed resonator and the influences of the thicknesses of the LiNbO₃, SiO₂, and Al electrodes on performances such as the parasitic noise, bandwidth, and electromechanical coupling coefficient are analyzed. Optimal parameters for the multi-layer piezoelectric structure are identified for offering large coupling up to 24%. Based on these findings, a single-port SAW resonator with an Al/41° Y-X LiNbO₃/SiO₂/poly-Si/Si substrate structure is fabricated. The experimental results align well with the simulation results; meanwhile, the SAW filter based on the proposed resonator demonstrates that a center frequency of 2.3 GHz, a 3-dB fractional bandwidth of 23.48%, and a minimum in-band insertion loss of only 0.343 dB are simultaneously achieved. This study provides guidance for the development of multi-layer film SAW resonator-based filters with high-performance. Full article

Standing surface acoustic wave (SSAW)-based acoustofluidics is widely used due to its compatibility with soft materials and polymer structures. In the presence of an acoustic field, particles move either toward pressure nodes or anti-nodes according to their contrast factor. Using this technique, blood cells with a certain characteristic can be oriented in different streamlines in a microchannel. The cumulative effect of parameters, such as the inlet velocity ratio of the buffer solution to the blood sample, acoustic frequency, voltage, and channel geometry, is key to effective separation in these microfluidic chips. In this study, simultaneous separation of white blood cells, red blood cells, and platelets in one stage is simulated by means of numerical calculations. The linear constitutive equation for the piezoelectric substrate, the Helmholtz equation for the acoustic field, and the Navier–Stokes equations for fluid mechanics are solved simultaneously to precisely capture the blood cell behavior in the SSAW-based device. The results show that whole blood cell separation can be achieved using a velocity ratio of 6.25, a resonance frequency of 8.28 MHz, and a voltage of 8.5 V in the proposed five-outlet microfluidic chip. Full article

La₃Ga₅SiO₁₄ (langasite, LGS)-based surface acoustic wave (SAW) devices are widely used for industrial health monitoring in harsh high-temperature environments. However, a conventional LGS-based SAW structure has a low quality factor (Q) due to its spurious resonant peaks. A hetero-acoustic layer (HAL)-based structure can effectively enhance the Q factor and the figure of merit (FOM) of SAWs due to its better energy confinement of SAWs. In this work, a HAL-based structure is proposed to achieve a high FOM and high-temperature resistance at the same time. Based on the finite element method (FEM) and coupling-of-model (COM) combined simulation, a systematic numerical investigation was conducted to find the optimal materials and structural parameters considering the viability of an actual fabricating process. After optimizing the layer number, an intermediate-layer material choice and structural parameters, Pt/(0°, 138.5°, 27°) LGS/YX-LGS/SiC HAL structure were chosen. The proposed structure achieves a Q factor and FOM improvement of more than 5 and 2.6 times higher than those of conventional SAW structures, which is important for the development of high temperature SAW sensors. These findings pave a viable method for improving the Q factor and FOM of LGS-based SAW and can provide material and device structural design guidance for fabrication and high-temperature applications in the future. Full article