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A magnetic surface acoustic wave (SAW) sensor is built by growing a 100 nm galfenol (Fe72Ga28) film by sputtering between the interdigitated transducers of a SAW delay line. Love waves are produced when the shear waves excited on the piezoelectric substrate are guided by a 3.1 μm layer of amorphous SiO2. Due to the magnetostrictive nature of galfenol deposited on top, the application of magnetic fields modulates the propagation of the mechanical excitations along the sensor by the strain coupling. By introducing the delay line in a feedback loop circuit, these changes are studied as resonant frequency variations. Magnetic field cycles of ±40 mT are applied to the sample and the resonant frequency shift is tracked simultaneously. The sensor exhibited hysteretic frequency behavior that depends on the orientation of the applied magnetic field relative to the direction of Love wave propagation. In the configuration in which the wave vector and the applied field form an angle of 45°, the resonant frequency seems to increase with the magnetization induced by the external field. When the wave vector propagation is parallel to the field, two positive peaks appear close to the coercive field of the film, which has not been reported before. This is probably due to a more complex relationship between the acoustic wave and the magnetic state of the film which could be exploited to give rise to new models of magnetic sensors. [ABSTRACT FROM AUTHOR]

The use of voltage induced strain to switch magnetic tunnel junctions (MTJs) is a promising solution for reducing the switching energy in MRAM technologies. The MTJ is integrated with a piezoelectric layer to generate the strain. A very thin layer is needed to switch with small voltages and small energy dissipation. It is challenging to synthesize ultrathin piezoelectric layers that retain a high degree of piezoelectricity. An alternate approach is to use time-varying strain generated by a surface acoustic wave (SAW). This approach does not require a thin piezoelectric layer since the SAW is confined to the surface of the layer. In this study, we fabricated in-plane MTJs on piezoelectric LiNbO3 substrates and used IDTs to generate the SAW signal within the substrate. Our results showed that the SAW signal had a significant influence on the resistance and the tunneling magnetoresistance (TMR) ratio of the MTJs. The influence was much less significant in nanometer size MTJs than in micrometer sized ones. Most surprisingly, the SAW signal caused the tunneling magnetoresistance ratio (TMR) to drop below zero for the micrometer size MTJ, meaning that the antiparallel resistance RAP is temporarily less than the parallel resistance RP under SAW excitation. Our results provide insight into the dynamic behavior of MTJs under periodic strain and the dependence of this behavior on the device dimensions as they are scaled down to nanometer sizes. [ABSTRACT FROM AUTHOR]

We present a surface acoustic wave (SAW) sensor array for microRNA (miRNA) detection that utilizes photocatalytic silver staining on titanium dioxide (TiO2) nanoparticles as a signal enhancement technique for high sensitivity with an internal reference sensor for high reproducibility. A sandwich hybridization was performed on working sensors of the SAW sensor array that could simultaneously capture and detect three miRNAs (miRNA-21, miRNA-106b, and miRNA-155) known to be upregulated in cancer. Sensor responses due to signal amplification varied depending on the concentration of synthetic miRNAs. It was confirmed that normalization (a ratio of working sensor response to reference sensor response) screened out background interferences by manipulating data and minimized non-uniformity in the photocatalytic silver staining step by suppressing disturbances to both working sensor signal and reference sensor signal. Finally, we were able to successfully detect target miRNAs in cancer cell-derived exosomal miRNAs with performance comparable to the detection of synthetic miRNAs. [ABSTRACT FROM AUTHOR]

In this study, we used simulation to investigate the optimal working point of a surface acoustic wave-magnetostriction sensor by varying the thickness of the magnetic sensitive layer using the finite elements method. We evaluated the sensor's sensitivity by simulating the responses at the optimal point and changing the thickness of the magnetic sensitive layer (h3). Additionally, we reduced the piezoelectric substrate thickness (h1) at the optimal point to determine the limit point of the center frequency (f0) and improve the sensor sensitivity for low magnetic field intensity measurements by performing a wavelength reduction (1). For the simulation, we selected a delay-line FeNi/IDT/AlN structure with specific materials and electrode parameters. Our results show that the optimal structure of the sensor is at h1=400 µm, 1=40 µm, and h3=1,060 nm, with a maximum f0 of 140.38493 MHz and maximum surface acoustic wave velocity of 5,615.4 m/s. At this optimal structure, the sensitivity reaches the maximum value of 10.287 kHz/Oe with a working range from 0 to 89 Oe. We also found that reducing the piezoelectric substrate thickness to 35 µm significantly reduces the manufacturing and simulation time, but the frequency response cannot determine the center frequency. [ABSTRACT FROM AUTHOR]

This paper aimed at studying the effect of initial stress and impedance boundary surface on the elastic waves propagation in transversely isotropic materials. The governing equations of transversely isotropic materials with initial stress are treated in the x y -plane to obtain the phase velocities of two waves, quasi-longitudinal (q P) and quasi-transverse (q S) waves. The normal mode operation is employed to obtain the expression of the displacement components and stress components. The problem of reflection of incident waves at the impedance boundary of transversely isotropic material is also investigated in the presence of initial stress to obtain the amplitude ratios of reflected waves. The variations of displacement and force stress are illustrated with respect to the axis of propagation by employing amplitude ratio expression. The effect of initial stress and impedance parameters on the expression of displacement and force stress as well as amplitude ratios of transversely isotropic materials are illustrated graphically for a particular model. [ABSTRACT FROM AUTHOR]

The article presents the design concept of a surface acoustic wave (SAW)-based lab-on-a-chip sensor with multifrequency and multidirectional sensitivity. The conventional SAW sensors use delay lines that suffer from multiple signal losses such as insertion, reflection, transmission losses, etc. Most delay lines are designed to transmit and receive continuous signal at a fixed frequency. Thus, the delay lines are limited to only a few features, like frequency shift and change in wave velocity, during the signal analysis. These facts lead to limited sensitivity and a lack of opportunity to utilize the multi-directional variability of the sensing platform at different frequencies. Motivated by these facts, a guided wave sensing platform that utilizes simultaneous tone burst-based excitation in multiple directions is proposed in this article. The design incorporates a five-count tone burst signal for the omnidirectional actuation. This helps the acquisition of sensitive long part of the coda wave (CW) signals from multiple directions, which is hypothesized to enhance sensitivity through improved signal analysis. In this article, the design methodology and implementation of unique tone burst interdigitated electrodes (TB-IDT) are presented. Sensing using TB-IDT enables accessing multiple frequencies simultaneously. This results in a wider frequency spectrum and allows better scope for the detection of different target analytes. The novel design process utilized guided wave analysis of the substrate, and selective directional focused interdigitated electrodes (F-IDT) were implemented. The article demonstrates computational simulation along with experimental results with validation of multifrequency and multidirectional sensing capability. [ABSTRACT FROM AUTHOR]

Atherosclerosis is an inflammatory disease of the arteries associated with alterations in lipid and other metabolism and is a major cause of cardiovascular disease (CVD). LDL consists of several subclasses with different sizes, densities, and physicochemical compositions. Small dense LDL (sd-LDL) is a subclass of LDL. There is growing evidence that sd-LDL-C is associated with CVD risk, metabolic dysregulation, and several pathophysiological processes. In this study, we present a straightforward membrane device filtration method that can be performed with simple laboratory methods to directly determine sd-LDL in serum without the need for specialized equipment. The method consists of three steps: first, the precipitation of lipoproteins with magnesium harpin; second, the collection of effluent from a 100 nm filter; and third, the quantification of sd-LDL-ApoB in the effluent with an SH-SAW biosensor. There was a good correlation between ApoB values obtained using the centrifugation (y = 1.0411x + 12.96, r = 0.82, n = 20) and filtration (y = 1.0633x + 15.13, r = 0.88, n = 20) methods and commercially available sd-LDL-C assay values. In addition to the filtrate method, there was also a close correlation between sd-LDL-C and ELISA assay values (y = 1.0483x − 4489, r = 0.88, n = 20). The filtration treatment method also showed a high correlation with LDL subfractions and NMR spectra ApoB measurements (y = 2.4846x + 4.637, r = 0.89, n = 20). The presence of sd-LDL-ApoB in the effluent was also confirmed by ELISA assay. These results suggest that this filtration method is a simple and promising pretreatment for use with the SH-SAW biosensor as a rapid in vitro diagnostic (IVD) method for predicting sd-LDL concentrations. Overall, we propose a very sensitive and specific SH-SAW biosensor with the ApoB antibody in its sensitive region to monitor sd-LDL levels by employing a simple delay-time phase shifted SH-SAW device. In conclusion, based on the demonstration of our study, the SH-SAW biosensor could be a strong candidate for the future measurement of sd-LDL. [ABSTRACT FROM AUTHOR]

With the development of communications technology, surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices have become hotspots of the competitive research in the frequency band above GHz. It imposes higher requirements on the operating frequency, temperature coefficient of frequency (TCF), and electromechanical coupling coefficient (k2) of SAW devices. In this work, we reported on a novel ZnO/SiO2/diamond-layered resonator structure and systematically investigated its propagation characteristics by using finite element methods. A comparative study and analysis of k2 and acoustic velocity (vp) for both the excited Rayleigh mode and the Sezawa mode were conducted. By selecting the appropriate ZnO piezoelectric film, SiO2, and electrode thickness, the Sezawa mode was chosen as the main mode, effectively improving both k2 and vp. It was observed that the k2 of the Sezawa mode is 7.5 times that of the excited Rayleigh mode and nearly 5 times that of piezoelectric single-crystal ZnO; vp is 1.7 times that of the excited Rayleigh mode and nearly 1.5 times that of piezoelectric single-crystal ZnO. Furthermore, the proposed multilayer structure achieves a TCF close to 0 while maintaining a substantial k2. In practical applications, increasing the thickness of SiO2 can compensate for the device's TCF reduction caused by the interdigital transducer (IDT). Finally, this study explored the impact of increasing the aperture width and IDT pairs on the performance of the single-port resonator, revealing the changing patterns of quality factor (Q) values. The results reported here show that the structure has great promise for the fabrication of high-frequency and low-TCF SAW devices. [ABSTRACT FROM AUTHOR]

The application of standing surface acoustic wave (SSAW) tweezers based on backpropagation superposition to achieve precise behavior manipulation of microscale cells and even nanoscale bacteria has been widely studied and industrialized. However, the structure requires multiple transducer components or full channel resonance. It is very challenging to design a simple structure for nano-control by complex acoustic field. In this study, a reflector-interdigital transducer (R-IDT) acoustofluidic device based on unilateral coherence enhancement is proposed to achieve SSAW definition features of periodic particle capture positions. The SAW device based on a unilateral transducer can not only generate leaky-SAW in water-filled microchannel, but also have a contribution of spherical waves in the vibration area of the substrate-liquid interface due to the Huygens-Fresnel diffractive principle. Both of them form a robust time-averaged spatial periodicity in the pressure potential gradient, accurately predicting the lateral spacing of these positions through acoustic patterning methods. Furthermore, a reflector based on Bragg-reflection is used to suppress backward transmitted SAW and enhance forward conducted SAW beams. By using a finite element model, R-IDT structure's amplitude enhances 60.78% compared to single IDT structure. The particle manipulation range of the diffractive acoustic field greatly improves, verified by experimental polystyrene microspheres. Besides, biocompatibility is conformed through red blood cells and Bacillus subtilis. We investigate the overall shift of periodic pressure field that can still occur when the phase changes. This work provides a simpler and low-cost solution for the application of acoustic tweezer in biological cell culture and filtering. [ABSTRACT FROM AUTHOR]

In this paper, the Zeolitic imidazole framework (ZIF) is designed and synthesized as the anti-interference layer of the Palladium–Nickel (PdNi) alloy thin-film coated surface acoustic wave (SAW) hydrogen (H 2) sensing device. Dimension regulation of the ZIF is conducted to obtain superior interference immunity. The two-dimensional (2D) and three-dimensional (3D) ZIF are prepared on top of PdNi thin-films by drop-coating. The gas experimental results indicate that 2D ZIF@PdNi sensors are more sensitive than 3D ZIF@PdNi and pure PdNi. At ambient temperature (25 °C), a fast response/recovery time of 12.03/14.62 s towards 8% H 2 gas, an ultralow limit of detection of 5 ppm, and a significantly increased sensitivity of 16.77 mV/% are achieved. Additionally, the 2D ZIF@PdNi sensors feature outstanding selectivity for H 2 gas against other gases (CO/NH 3 /H 2 S), good reversibility, and long-term stability for 30 days. The improved H 2 sensing performance can be attributed to that the two-dimensional anti-interference layer (2D ZIF) is more conducive to the diffusion of gas molecules, which in turn increases the interaction between PdNi and the target gas. • The design of the anti-interference layers on PdNi films can improve H 2 sensing performance. • Zeolitic imidazole frameworks (ZIF) are potential candidate anti-interference layers. • Dimension regulation of the ZIF is conducted to achieve superior interference immunity. • The PdNi composited with two-dimensional ZIF layer shows outstanding sensing behavior. [ABSTRACT FROM AUTHOR]

Enhancement of nanoscale confinement in the subwavelength waveguide is a concern for advancing future photonic interconnects. Rigorous innovation of plasmonic waveguide-based structure is crucial in designing a reliable on-chip optical waveguide beyond the diffraction limit. Despite several structural modifications and architectural improvements, the plasmonic waveguide technology is far from reaching its maximum potential for mass-scale applications due to persistence issues such as insufficient confined energy and short propagation length. This work proposes a new method to amplify the propagating plasmons through an external on-chip surface acoustic signal. The gold–silicon dioxide (Au-SiO2) interface, over Lithium Niobate (LN) substrate, is used to excite propagating surface plasmons. The voltage-varying surface acoustic wave (SAW) can tune the plasmonic confinement to a desired signal energy level, enhancing and modulating the plasmonic intensity. From our experimental results, we can increase the plasmonic intensity gain of 1.08 dB by providing an external excitation in the form of SAW at a peak-to-peak potential swing of 3 V, utilizing a single chip. [ABSTRACT FROM AUTHOR]

Long-term monitoring of environmental warfare agengts is a challenge for chemical gas sensors. To address this issue, we developed a 433 MHz passive wireless surface acoustic wave (WSAW) gas sensor for dimethyl methylphosphonate (DMMP) detection. This WSAW gas sensor includes a YZ lithium niobate (LiNbO3) substrate with metallic interdigital transducers (IDTs) etched on it, and an antenna was placed near the IDT. A DMMP-sensitive viscoelastic polymer fluoroalcoholpolysiloxane (SXFA) film was prepared on a LiNbO3 substrate, and mode modeling coupling was used to optimize the design parameters. The sensor can function properly in an environments between −30 °C and 100 °C with humidity less than 60% RH. When the wireless transmission distance was within the range of 0–90 cm, the sensor noise increased with distance, and the stability was less than 32°/h. While optimizing the film thickness of SXFA, a relationship was observed between sensor sensitivity and film thickness. When the film thickness of SXFA reached 450 nm, the optimal value was reached. At a distance of 20 cm between the transmitting and receiving antennas, DMMP was detected at different concentrations with the developed WSAW gas sensor. The lower detection limit of DMMP was 0.48 mg/m3, the sensitivity of the sensor was 4.63°/(mg/m3), and repeatable performance of the sensor was confirmed. [ABSTRACT FROM AUTHOR]

This work is devoted to problems arising in calculation of parameters of surface acoustic waves (SAWs) of the main and multiple frequency harmonics using the finite element method. The technique and main features of the SAW analysis by a numerical method are considered. Simple one-wavelength test cells were chosen as the main mode of the study. It is shown that, using these SAW parameters in the analytical modified coupling-of-modes model, one can preliminarily calculate amplitude–frequency responses of SAW devices using higher-order frequency harmonics. The calculation results are compared with experimental measurements of the transfer coefficients of SAW filter and SAW delay line. [ABSTRACT FROM AUTHOR]

This paper theoretically investigates the influence of homo- and hetero-junctions on the propagation characteristics of radially propagated cylindrical surface acoustic waves in a piezoelectric semiconductor semi-infinite medium. First, the basic equations of the piezoelectric semiconductor semi-infinite medium are mathematically derived. Then, based on these basic equations and the transfer matrix method, two equivalent mathematical models are established concerning the propagation of radially propagated cylindrical surface acoustic waves in this piezoelectric semiconductor semi-infinite medium. Based on the surface and interface effect theory, the homo- or hetero-junction is theoretically treated as a two-dimensional electrically imperfect interface in the first mathematical model. To legitimately confirm the interface characteristic lengths that appear in the electrically imperfect interface conditions, the homo- or hetero-junction is equivalently treated as a functional gradient thin layer in the second mathematical model. Finally, based on these two mathematical models, the dispersion and attenuation curves of radially propagated cylindrical surface acoustic waves are numerically calculated to discuss the influence of the homo- and hetero-junctions on the dispersion and attenuation characteristics of radially propagated cylindrical surface acoustic waves. The interface characteristic lengths are legitimately confirmed through the comparison of dispersion and attenuation curves calculated using the two equivalent mathematical models. As piezoelectric semiconductor energy harvesters usually work under elastic deformation, the establishment of mathematical models and the revelation of physical mechanisms are both fundamental to the analysis and optimization of micro-scale surface acoustic wave resonators, energy harvesters, and acoustic wave amplification based on the propagation of surface acoustic waves. [ABSTRACT FROM AUTHOR]

The increasing threat of nerve agents has prompted the need for gas sensors with fast response, high sensitivity, and good stability. In this work, the hexafluoroisopropanol functional group was modified on a porous aromatic framework material, which served as a sensitive material for detecting dimethyl methylphosphonate. A nerve agent sensor was made by coating sensitive materials on a surface acoustic wave device. Lots of pores in sensitive materials effectively increase the specific surface area and provide channels for diffusion of gas molecules. The introduction of hexafluoroisopropanols enables the sensor to specifically adsorb dimethyl methylphosphonate and improves the selectivity of the sensor. As a result, the developed gas sensor was able to detect dimethyl methylphosphonate at 0.8 ppm with response/recovery times of 29.8/43.8 s, and the detection limit of the gas sensor is about 0.11 ppm. The effects of temperature and humidity on the sensor were studied. The results show that the baseline of the sensor has a linear relationship with temperature and humidity, and the temperature and humidity have a significant effect on the response of the sensor. Furthermore, a device for real-time detection of nerve agent is reported. This work provides a new strategy for developing a gas sensor for detecting nerve agents. [ABSTRACT FROM AUTHOR]

Thin film technology shows great promise in fabricating electronic devices such as gas sensors. Here, we report the fabrication of surface acoustic wave (SAW) sensors based on thin films of (1 − x) Ba(Ti0.8Zr0.2)O3−x(Ba0.7Ca0.3)TiO3 (BCTZ50, x = 50) and Polyethylenimine (PEI). The layers were deposited by two laser-based techniques, namely pulsed laser deposition (PLD) for the lead-free material and matrix assisted pulsed laser evaporation (MAPLE) for the sensitive polymer. In order to assay the impact of the thickness, the number of laser pulses was varied, leading to thicknesses between 50 and 350 nm. The influence of BCTZ film's crystallographic features on the characteristics and performance of the SAW device was studied by employing substrates with different crystal structures, more precisely cubic Strontium Titanate (SrTiO3) and orthorhombic Gadolinium Scandium Oxide (GdScO3). The SAW sensors were further integrated into a testing system to evaluate the response of the BCTZ thin films with PEI, and then subjected to tests for N2, CO2 and O2 gases. The influence of the MAPLE's deposited PEI layer on the overall performance was demonstrated. For the SAW sensors based on BCTZ/GdScO3 thin films with a PEI polymer, a maximum frequency shift of 39.5 kHz has been obtained for CO2; eight times higher compared to the sensor without the polymeric layer. [ABSTRACT FROM AUTHOR]

The uniformity in size of liquid metal droplets is crucial in determining the accuracy of flexible circuit printing as well as the stability in signal transmission. In this study, the numerical simulation and the experiment method are combined to analyze the droplet preparation process of liquid metal. Furthermore, the mechanism of the surface acoustic wave as an external force dominating the breakup of the liquid metal interface is investigated. The results show that the squeezing pressure and the capillary force are the dominant forces of the interface evolution in the low-aspect-ratio (height/width) channel. When the dispersed phase flow rate is low, the interface will retract upstream of the channel under the influence of large interfacial tension after breakup, resulting in fluctuations in flow rate, and therefore, the stability of droplet size is weak. When the dispersed phase flow rate is high, the interface randomly breaks up under the influence of the Rayleigh–Plateau instability, which also leads to uneven droplet size. As the acoustic intensity increases, the acoustic radiation pressure gradually becomes the dominant force responsible for the squeezing and breakup of the interface. It increases the radial contraction rate of the interface, shortens the droplet generation period, and ultimately reduces the droplet size. Additionally, the size deviation value is significantly reduced from 10.13% to 1.05%. This study is useful in elucidating the evolution mechanism of liquid metal interfaces in low-aspect-ratio channels, improving the fundamental theory of interface breakup caused by acoustic radiation pressure, and providing theoretical guidance for the controlled and stable production of liquid metal droplets. [ABSTRACT FROM AUTHOR]

Surface wave dispersion curves are widely used to constrain earth velocity structures and are important to compute theoretical synthetic seismograms with a mode-summation approach. While the computation of dispersion curves requires searching roots of nonlinear functions, some high-mode may be missed with improper choice of searching steps. The asymptotic distribution of eigenvalues of the elastic wave equation can be used as auxiliary information to design a sophisticated scheme to compute the surface wave dispersion curves. In this study, we show the Weyl's law, combined with the Liouville transformation, can be exploited to derive asymptotic eigenvalue counting functions of elastic surface waves in a horizontally stratified or radially heterogeneous medium. We also show the derived formulation according to the Weyl's law, in its simple case, agrees with previous studies. The derived asymptotic eigenvalue counting functions are validated by comparison with numerical results. This study demonstrates the Weyl's law can be used to derive eigenvalue counting functions of surface waves in elastic media, and it is also possible to be applied to more complex media. [ABSTRACT FROM AUTHOR]

Diabetes mellitus is a metabolic disease characterized by increased blood sugar levels above normal limits. This disease has a very high risk of death so it needs to be recognized early. Currently, testing blood sugar levels still uses invasive techniques, namely taking examination samples by drawing blood using a syringe, which causes pain in the sufferer's body. This causes some patients to be reluctant to check their blood sugar. Therefore, it is essential to create a tool that can measure blood sugar levels accurately without having to injure the body of diabetes mellitus sufferers, which is called a non-invasive method. Based on these problems and previous research references, this research will develop a tool for recognizing urine odor patterns in Diabetes Mellitus (DM) sufferers by using e-nose equipment. In designing this tool, gas sensors have been used, namely MQ-135, MQ-4, TGS2 2600, TGS 2602, and a Surface Acoustic Wave (SAW) sensor to detect urine smell through the evaporation process. It uses the backpropagation algorithm as an Artificial Neural Network (ANN) method for the process of recognizing patterns produced from steam samples. From the 35 test data carried out, the system could recognize patterns from the urine samples tested with a success rate of 94%. The significance of this research is that it is a tool for early detection of non-invasive DM disease. [ABSTRACT FROM AUTHOR]

The addition of surface acoustic wave (SAW) technologies to microfluidics has greatly advanced lab-on-a-chip applications due to their unique and powerful attributes, including high-precision manipulation, versatility, integrability, biocompatibility, contactless nature, and rapid actuation. However, the development of SAW microfluidic devices is limited by complex and time-consuming micro/nanofabrication techniques and access to cleanroom facilities for multistep photolithography and vacuum-based processing. To simplify the fabrication of SAW microfluidic devices with customizable dimensions and functions, we utilized the additive manufacturing technique of aerosol jet printing. We successfully fabricated customized SAW microfluidic devices of varying materials, including silver nanowires, graphene, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). To characterize and compare the acoustic actuation performance of these aerosol jet printed SAW microfluidic devices with their cleanroom-fabricated counterparts, the wave displacements and resonant frequencies of the different fabricated devices were directly measured through scanning laser Doppler vibrometry. Finally, to exhibit the capability of the aerosol jet printed devices for lab-on-a-chip applications, we successfully conducted acoustic streaming and particle concentration experiments. Overall, we demonstrated a novel solution-based, direct-write, single-step, cleanroom-free additive manufacturing technique to rapidly develop SAW microfluidic devices that shows viability for applications in the fields of biology, chemistry, engineering, and medicine. [ABSTRACT FROM AUTHOR]

Controlling acoustic streaming inside a droplet has excellent potential for enabling fluid and particle operations such as mixing, separation, and aggregation in various applications. Most concepts for generating surface acoustic waves are based on the placement of an interdigitated transducer at the side of a droplet, thus externally acting on the droplet. In this case, the flow structure inside the droplet is controlled by the relatively large scale of the interdigitated transducer compared to the droplet, thus limiting the local control of the flow. One possibility to overcome this drawback is to reduce the size of the actuator such that a highly focused ultrasound transducer can induce localized acoustic streaming in space. Here, we introduce a micro‐spiral interdigitated transducer smaller than a droplet size that can generate micro‐size vortices inside the droplet. This step enables a new way of controlling the flow inside the droplet, facilitating mixing, separation, aggregation, and patterning of particles. We study the characteristics of the acoustic streaming and the potential application of the flow for the separation and patterning of particles. The simplicity of the concept provides in‐droplet particle manipulation toolsets for many applications such as biosensing, microbiology, and point‐of‐care devices. [ABSTRACT FROM AUTHOR]

Highly sensitive surface acoustic wave (SAW) sensors have recently been recognized as a promising tool for various industrial and medical applications. However, existing SAW sensors generally suffer from a complex design, large size, and poor robustness. In this paper, we develop a simple and stable delay line ultra-high frequency (UHF) SAW sensor for highly sensitive detection of temperature. A Z-shaped delay line is specially designed on the piezoelectric substrate to improve the sensitivity and reduce the substrate size. Herein, the optimum design parameters of extremely short-pitch interdigital transducers (IDTs) are given by numerical simulations. The extremely short pitch gives the SAW sensor ultra-high operating frequency and consequently ultra-high sensitivity. Several experiments are conducted to demonstrate that the sensitivity of the Z-shaped SAW delay line sensor can reach up to 116.685°/°C for temperature detection. The results show that the sensor is an attractive alternative to current SAW sensing platforms in many applications. [ABSTRACT FROM AUTHOR]

To ensure that surface acoustic wave (SAW) filters fulfill the requirements of Carrier Aggregation (CA) applications, the development of modeling tools that can forecast and simulate high-frequency spurious responses has been necessary. This paper presents an advanced methodology for extending the coupling-of-modes (COM) model to obtain precise modeling of the high-frequency spurious responses of incredible high-performance surface acoustic wave (I.H.P. SAW) devices. The extended COM (ECOM) model is derived by modifying the conventional COM model and extending it accordingly. The parameters used in this model are determined through numerical fitting. For validation, firstly, the ECOM model is applied to a one-port synchronous I.H.P. SAW resonator, and the simulation and measurement results match. Then, the structural parameters of the ECOM model are varied, and the accuracy of the model after the structural parameters are varied is verified. It is demonstrated that this model can be applied to the design work of SAW filters. Finally, the ECOM model is applied to the design of the I.H.P. SAW filter based on a 42°YX-LiTaO3 (LT)/SiO2/AlN/Si structure. By using this method, the I.H.P. SAW filter's high-frequency spurious response can be predicted more accurately. [ABSTRACT FROM AUTHOR]

This study designs antenna-plexers, including a surface acoustic wave (SAW) extractor and an upper- and mid-high band (UHB + MHB) diplexer, for LTE 4G and 5G bands using carrier aggregation. The SAW extractor combines a bandpass filter (BPF) and a band-stop filter (BSF) in a single unit that consists of eight modified Butterworth–van Dyke (mBVD) resonators that resonate in parallel with an inductor and SAW resonators. This BSF behaves as a high-pass filter at frequencies lower than the designed WIFI band and as a capacitor at higher frequencies. The SAW extractor meets product specifications in the frequency range 0.7 to 2.7 GHz. The UHB + MHB diplexer, which is composed of a microwave filter, a SAW filter, and a simple matching inductor, uses frequency response methods to create an RF component for 2.4 GHz + WIFI 6E applications. The design uses a SAW's interdigital transducer (IDT) structure, and the experimental results are in agreement with the simulation results, so the design is feasible. [ABSTRACT FROM AUTHOR]

SAW devices with a multi-layered piezoelectric substrate have excellent performance due to advantages such as a high quality factor, Q, low loss insertion, large bandwidth, etc. Prior to manufacturing, a comprehensive analysis and proper design are essential to evaluating the device's key performance indicators, including the Bode Q value, bandwidth, and transverse mode suppression. This study explored the performance of SAW resonators employing a 42°Y-X LiTaO3 (LT) thin-plate-based multi-layered piezoelectric substrate. The thicknesses for each layer of the 42°Y-X LT/SiO2/poly-Si/Si substrate were optimized according to the index of phase velocity, Bode Q value, and bandwidth. The effect of the device structure parameters on the dispersion curve and slowness curve was studied, and a flat slowness curve was found to be favorable for transverse mode suppression. In addition, the design of the dummy configuration was also optimized for the suppression of spurious waves. Based on the optimized design, a one-port resonator on the 42°Y-X LT/SiO2/poly-Si/Si substrate was fabricated. The simulation results and measurements are presented and compared, which provides guidelines for the design of new types of SAW devices configured with complex structures. [ABSTRACT FROM AUTHOR]

With the development of ink jet printers or spotters for biological applications, the control size and homogeneity of small fluids as well as their successful deposition on various substrates has gained significant importance. We study the impingement process of such small droplets onto a solid substrate and investigate their evaporation and drying process by means of surface acoustic wave (SAW) transmission experiments. We observe a strong fluid-SAW interaction resulting in an attenuation which toward the end of the evaporation and drying process exhibits characteristic oscillations being related to temperature, SAW amplitude, and fluid properties such as viscosity and wetting angle. It is found that oscillations can only be seen in pinned, very flat droplets, while the pinning can be roughly controlled via the SAW amplitude. The frequency of those characteristic oscillations is superlinear with respect to temperature, rather proportional to the evaporation rate and can change drastically depending on the liquid used. In our experiments, isopropanol, ethanol, and water with various glycerol concentrations were loaded onto the SAW delay line. Based on the experimental results, simulations using the finite element method were performed. We find that a standing wave pattern within the droplet is responsible for the transmission oscillations. These findings might lead to new methods, e.g., sensory systems, being able to examine droplets according to their physical or chemical properties. [ABSTRACT FROM AUTHOR]

A variety of multidispersive, localized, or extended in frequency, bands, induced by inductance-based external electric circuits in piezoelectric phononic plates, is studied both theoretically and experimentally in this work. Their origin, tightly related to an equivalent L C -circuit behavior, is analyzed in detail and their interaction with the Lamb-like guided modes of the plate is also discussed. These bands, easily tuned by the choice of the parameters of the external electric circuitry, lead to a non-destructive, real-time control of the dispersion characteristics of these structures. Our device and analysis can find application in the improvement of surface acoustic wave components by offering additional degrees of freedom. [ABSTRACT FROM AUTHOR]

Short pulse laser irradiation of a substrate can generate pulses of surface acoustic waves (SAWs) capable of propagating long distances along the surface of the irradiated substrate. In this work, we use thermoelastic modeling of the generation of SAWs on a Si substrate to explore the effect of irradiation parameters, i.e., pulse duration, laser spot size, absorption depth, and spatial profile of the laser energy deposition, on the strength of the SAWs. A particular goal of this study is to establish the optimum conditions for maximizing the strength of the surface waves generated in the nonablative, thermoelastic irradiation regime. The simulations demonstrate that the highest strain amplitude of the laser-generated SAWs can be achieved for a laser spot size comparable to the characteristic length of the SAW propagation during the laser pulse. The amplitude of SAWs increases with the increase in the characteristic laser energy deposition depth, and laser pulses with sharper spatial energy deposition profiles (flat-top laser beams) produce stronger SAWs. For the optimal set of irradiation parameters, the strain amplitude of a SAW generated in Si in the thermoelastic regime can reach the levels of 10−4–10−3, which are sufficiently high for causing nonlinear sharpening of the wave profile and the formation of a shock front during the wave propagation from the laser spot. The computational predictions suggest the feasibility of a continuous generation of strong nonlinear pulses of SAWs, which may be utilized for driving the surface processes in thin film deposition, growth of two-dimensional materials, heterogeneous catalysis, and other applications. [ABSTRACT FROM AUTHOR]

In this work, surface acoustic wave (SAW) modes and their dependence on propagation directions in epitaxial Al 0.68 Sc 0.32 N(0001) films on Al 2 O 3 (0001) substrates were studied using numerical and experimental methods. In order to find optimal propagation directions for higher-order SAW modes, phase velocity dispersion branches of Al 0.68 Sc 0.32 N on Al 2 O 3 with Pt mass loading were computed for the propagation directions <11 2 ¯ 0> and <1 1 ¯ 00> with respect to the substrate. Experimental investigations of phase velocities and electromechanical coupling were performed for comparison with the numerical results. Simulations carried out with the finite element method and a Green function approach allowed identification of each wave type, including Rayleigh, Sezawa, and shear-horizontal wave modes. For the propagation direction <1 1 ¯ 00>, significantly increased wave guidance of the Sezawa mode compared to other directions was observed, resulting in enhanced electromechanical coupling (k eff 2 = 1.6 %) and phase velocity (v phase = 6 km / s). We demonstrated that selecting wave propagation in <1 1 ¯ 00> with high mass density electrodes results in increased electromechanical coupling without significant reduction in phase velocities for the Sezawa wave mode. An improved combination of metallization, Sc concentration x , and SAW propagation direction is suggested that exhibits both high electromechanical coupling (k eff 2 > --> 6 %) and high velocity (v phase = 5.5 km / s) for the Sezawa mode. [ABSTRACT FROM AUTHOR]

We show that a surface acoustic wave (SAW) applied across the terminals of a magnetic tunnel junction (MTJ) decreases both the (time-averaged) parallel and antiparallel resistances of the MTJ, with the latter decreasing much more than the former. This results in a decrease in the tunneling magnetoresistance ratio. The coercivities of the free and fixed layers of the MTJ, however, are not affected significantly, suggesting that the SAW does not cause large-angle magnetization rotation in the magnetic layers through the inverse magnetostriction (Villari) effect at the power levels used. This study sheds light on the dynamical behavior of an MTJ under periodic compressive and tensile strain. [ABSTRACT FROM AUTHOR]

This study proposes a hybrid quantum system of an ensemble of collective spins coupled to a surface acoustic wave (SAW) cavity through a sideband design. Assisted by a dichromatic optical drive with a phase-dependent control, this spin ensemble can effectively mimic different types of long-range Lipkin–Meshkov–Glick (LMG) interactions and then undergo quantum phase transitions (QPTs) due to phase-induced spontaneous symmetry breaking (SSB). In addition, this phase-controlled scheme also ensures the dynamical preparation of the spin-squeezed state (SSS), which may be a useful application in quantum measurement. This study is a fresh attempt at quantum manipulation based on acoustic control and also provides a promising route toward useful applications in quantum information processing, especially the adiabatic preparation of multiparticle-entangled ground states via QPTs; i.e., the Greenberger–Horne–Zeilinger (GHZ) or W-type states. [ABSTRACT FROM AUTHOR]

One approach to extend the acoustic applications of aluminum nitride (AlN) in the GHz frequency range is to take advantage of the piezoelectric performance and high acoustic velocity (∼11 350 m/s) along the c-axis of this material. In particular, in the case of high-frequency micro-electromechanical systems, it should be possible to simplify the construction of resonators by using a-plane AlN-based structures. In the work described in this Letter, a single-crystalline a-plane AlN layer on an r-plane sapphire substrate is obtained by combining sputtering and high-temperature annealing. Based on this non-polar AlN, a resonator with only planar interdigital transducer electrodes is fabricated. Experiments on this resonator reveal simultaneous excitation of an anisotropic Rayleigh surface acoustic wave (SAW) at 2.38 GHz and a laterally excited bulk acoustic wave (LBAW) at 4.00 GHz. It is found that the Rayleigh SAW exhibits outstanding performance, with a quality factor as high as 2458 and great stability under variations in temperature. The LBAW at 4.00 GHz is excited by pure planar interdigitated electrodes without the need for any cavity or bottom electrode structure, thus demonstrating a promising approach to the construction of high-frequency resonators with a relatively simple structure. [ABSTRACT FROM AUTHOR]

Surface acoustic wave resonators are widely applied in electronics, communication, and other engineering fields. However, the spurious modes generally present in resonators can cause deterioration in device performance. Therefore, this paper proposes a hexagonal weighted structure to suppress them. With the construction of a finite element resonator model, the parameters of the interdigital transducer (IDT) and the area of the dummy finger weighting are determined. The spurious waves are confined within the dummy finger area, whereas the main mode is less affected by this structure. To verify the suppression effect of the simulation, resonators with conventional and hexagonal weighted structures are fabricated using the micro-electromechanical systems (MEMS) process. After the S-parameter test of the prepared resonators, the hexagonal weighted resonators achieve a high level of spurious mode suppression. Their properties are superior to those of the conventional structure, with a higher Q value (10,406), a higher minimum return loss (25.7 dB), and a lower ratio of peak sidelobe (19%). This work provides a feasible solution for the design of SAW resonators to suppress spurious modes. [ABSTRACT FROM AUTHOR]

We study the acoustically driven spin wave resonance (ADSWR) in a Ni film sputtered on a 128° Y-cut lithium niobate (LiNbO3) substrate under the condition that the beam steering effect exists due to the surface acoustic waves (SAWs) transmitted along several selected crystal orientations. SAW devices with that effect exhibit significantly different ADSWR spectra from devices without it. By using the magnetoelastic coupling theory and finite element simulation associated with SAW, we find that the beam steering effect of magnetoacoustic waves has an important influence on the acoustic attenuation. The relationship between its group velocity direction and the magnetization vector can be used to define the magnetoacoustic wave mode. The mode affects acoustic attenuation magnitude, which can break the fourfold symmetry. Increasing its power flow angle will significantly increase the maximum acoustic attenuation caused by magnon–phonon coupling. [ABSTRACT FROM AUTHOR]

Passive wireless surface acoustic wave (SAW) resonant sensors are widely used in measuring pressure, temperature, and torque, typically detecting sensing parameters by measuring the echo signal frequency of SAW resonators. Therefore, the accuracy of echo signal frequency estimation directly affects the performance index of the sensor. Due to the exponential attenuation trend of the echo signal, the duration is generally approximately 10 μs, with conventional frequency domain analysis methods limited by the sampling frequency and data points. Thus, the resolution of frequency estimation is limited. Here, signal time-domain fitting combined with a genetic algorithm is used to estimate SAW echo signal frequency. To address the problem of slow estimation speed and poor timeliness caused by a conventional genetic algorithm, which needs to simultaneously estimate multiple parameters, such as signal amplitude, phase, frequency, and envelope, the Hilbert transform is proposed to remove the signal envelope and estimate its amplitude, and the fast Fourier transform subsection method is used to analyze the initial phase of the signal. The genetic algorithm is thereby optimized to realize the frequency estimation of SAW echo signals under a single parameter. The developed digital signal processing frequency detection system was monitored in real time to estimate the frequency of an SAW echo signal lasting 10 μs and found to have only 100 sampling points. The proposed method has a frequency estimation error within 3 kHz and a frequency estimation time of less than 1 s, which is eight times faster than the conventional genetic algorithm. [ABSTRACT FROM AUTHOR]

Motors driven by surface acoustic waves (SAWs) have been extensively investigated due to their potential applications in various environments. One of the problems we are confronted with is the lifetime of the substrate which supports SAWs since it becomes fragile when large-amplitude SAWs are excited on the substrate. In order to prolong the lifetime of the substrate, we propose to apply modulated driving voltage with a duty ratio to the interdigital transducers. With the implementation of such a proposal, we found an intriguing phenomenon which is out of expectation, i.e., when the driving voltage is high, the slider speed under modulated driving with a suitable duty ratio might be larger than that with the continuous driving. [ABSTRACT FROM AUTHOR]

Surface acoustic wave (SAW) devices have been used in biochemical assays due to their high sensitivity. The device sensitivity is a function of changes in the density and viscosity of the liquid. Here, we studied the effect of fluid viscosity using a 250 MHz quartz shear-horizontal (SH)-SAW biosensor by monitoring different concentrations of binary aqueous/glycerol solutions. In this study, the sensitivity of the biosensor was determined by fitting the data to models derived from perturbation theory. Measurements in water were used as the reference. For a 0% to 50% glycerol solution, an 87°–204° separation in the phase shift was observed. The slope of the plot of the phase shift vs (ηρ)0.5 was used to indicate the sensor's sensitivity. The sensitivity for our 250 MHz quartz SH-SAW sensors was calculated to be 3.7 × 1 0 − 3 m 2 s Kg . The corresponding mass sensitivity was determined to be 9.25 × 105 m 2 Kg . The limit of detection was calculated to be 36 picograms (pg), while the limit of quantification or LOQ was calculated to be 109 pg. Traditionally, liquid phase measurements have been challenging for SAW devices because liquids dampen the vibrating sensors severely. This problem has been largely solved using a transverse (shear) wave instead of the more popular longitudinal or Rayleigh waves. Liquid measurements are now possible using transverse waves, also known as shear waves, because transverse waves are only minimally attenuated by liquids. Shear-horizontal SAW sensors (SH-SAW) show great promise as label-free biosensors because of their ability to handle liquid samples. However, the viscosity of the liquid still induces loading effects and can be measured when the liquid is loaded onto the SH-SAW propagating surface (delay line). When the liquid above the delay line is perturbed by physical or chemical changes, such as binding to a receptor, it alters the propagating acoustic wave. The SH-SAW device can measure these changes in liquid properties as a change in the wave's phase compared to the original wave. The device's phase shift was recorded as a function of the changes in the density and viscosity of the binary glycerol solution and used to determine the sensitivity in the linear dynamic range of responses. [ABSTRACT FROM AUTHOR]

In this paper, the flow and particle trajectories, induced by standing surface acoustic waves (SSAWs) in a poly-dimethylsiloxane microchannel, are investigated by establishing a two-dimensional cross-sectional model with the finite element method and improved boundary conditions. Extensive parametric studies are conducted regarding the channel height, ranging from 0.2 to 4.0 times the spacing of the repetitive vertical interference pattern, to investigate its influences on the flow field and microparticle aggregation. The first-order flow field is found to be related to the channel height, exhibiting a periodic spatial distribution and oscillatory variation in its amplitude as the height changes. We theoretically analyze the propagation mechanism of the acoustic waves in the vertical direction and thus determine the periodicity of the wave interference pattern. Furthermore, we find that the speed of the particle aggregation is a function of the channel height, so the channel height can be optimized to maximize the strength of the first-order flow field and thus minimize the time of particle aggregation. The optimum heights can reduce the aggregation time by up to 76%. In addition, the acoustophoretic motions of microparticles exhibit a spatially dependent pattern when the channel height becomes larger than a quarter of the wavelength of the SAW, which can be explained by the change in the ratio between the radiation force and the streaming drag force from position to position. Our findings provide guidelines to the design and optimization of SSAW-based acoustofluidic devices. [ABSTRACT FROM AUTHOR]

The efficient breakage of one cell or a concentration of cells for releasing intracellular material such as DNA, without damaging it, is the first step for several diagnostics or treatment processes. As the cell membrane is easy to bend but resistant to stretching, the exposure of the cell to a shear rate during a short period of time can be sufficient to damage the membrane and facilitate the extraction of DNA. However, how to induce high shear stresses on cells in small microliter volumes samples has remained an elusive problem. Surface acoustic waves operating at high frequencies can induce acoustic streaming leading to shear rates sufficient to cell lysis. Lysis induced by acoustic streaming in sessile droplets has been investigated in the past from the lysis efficiency point of view. However, the effects of the velocity field and shear rate induced by acoustic streaming on the lysis process remain unexplored. Here, we study the lysis of AC16 human cardiomyocytes in microliter droplets under the effect of the shear rate induced by acoustic streaming. It is identified that for a given shear rate, the extracted DNA is also affected by the actuation period which can be attributed to a cycling process that leads to an accumulation of damage on the cell membrane. [ABSTRACT FROM AUTHOR]

We present a comprehensive study using finite element numerical analysis of the acoustic localized phonons supported by a gold nanoridges dimer-based multilayer design. The latter consists in a SiO2-substrate over which a gold film covered with a thin polymer is deposited. We investigate first the mechanical eigen-modes analysis of a single monomer ridge, where we find flexural and compressional type modes in the sub-GHz frequency range. This is realized by either setting the ridge in a periodic structure, which enables to get the dispersion curve of the modes, or by considering an isolated system bounded by perfect matched layers, where we use the equivalent of the local density of states to track the modes. A good agreement is obtained between the two methods. Similarly, we find in case of the coupled dimer ridges hybridized modes, namely the flexural and compressional modes of a monomer split-up into in- and -out-of-phase type modes. We demonstrate efficient coupling between the monomer/dimer localized phonons with surface acoustic waves (SAWs) as the simulated transmission spectra show dips at the frequencies of the monomer/dimer eigenmodes. For symmetry reasons, some of the dimer modes are expected to be optomechanically active. The proposed SAW-based device is meant to help design acousto-optic modulators or ultrasensitive sensors. [ABSTRACT FROM AUTHOR]

This paper presents an advanced method that combines coupling-of-modes (COM) theory and the finite element method (FEM), which enables the quick extraction of COM parameters and the accurate prediction of the electroacoustic and temperature behavior of surface acoustic wave (SAW) devices. For validation, firstly, the proposed method is performed for a normal SAW resonator. Then, the validated method is applied to analysis of an I.H.P. SAW resonator based on a 29°YX−LT/SiO2/SiC structure. Via optimization, the electromechanical coupling coefficient (K2) is increased up to 13.92% and a high quality (Q) value of 1265 is obtained; meanwhile, the corresponding temperature coefficient of frequency (TCF) is −10.67 ppm/°C. Furthermore, a double-mode SAW (DMS) filter with low insertion loss and excellent temperature stability is also produced. It is demonstrated that the proposed method is effective even for SAW devices with complex structures, providing a useful tool for the design of SAW devices with improved performance. [ABSTRACT FROM AUTHOR]

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2D materials are considered as potential candidates for the next generation of optoelectronic materials. However, their optical absorption is typically weak due to thickness limitations, greatly restricting the photodetection capabilities of devices. To enhance the photoelectric gain of 2D materials or devices and improve detection sensitivity, various modulation methods such as strain, electric field, and magnetic field are commonly introduced. Among them, surface acoustic wave (SAW) represents a unique and effective modulation approach. In this study, photodetectors are fabricated based on few‐layer MoS2 on a SAW delay line on a LiTaO3 substrate. The interaction between SAW and MoS2 successfully manipulates the optoelectronic performance of the MoS2‐based devices. Under the influence of SAW, the dark current of the devices is significantly reduced by more than two orders of magnitude, while the photocurrent remains almost unchanged, resulting in excellent photoresponse performance. The devices provide a promising pathway for high‐performance optoelectronic applications and reveal a new possibility for acoustic devices in optoelectronics. [ABSTRACT FROM AUTHOR]

The dynamic behavior of solid Si targets irradiated by nanosecond laser pulses is computationally studied with transient, thermοmechanical three-dimensional finite element method simulations. The dynamic phase changes of the target and the generation and propagation of surface acoustic waves around the laser focal spot are provided by a finite element model of a very fine uniformly structured mesh, able to provide high-resolution results in short and long spatiotemporal scales. The dynamic changes in the Si material properties until the melting regime are considered, and the simulation results provide a detailed description of the irradiated area response, accompanied by the dynamics of the generation and propagation of ultrasonic waves. The new findings indicate that, due to the low thermal expansion coefficient and the high penetration depth of Si, the amplitude of the generated SAW is small, and the time and distance needed for the ultrasound to be generated is higher compared to dense metals. Additionally, in the melting regime, the development of high nonlinear thermal stresses leads to the generation and formation of an irregular ultrasound. Understanding the interaction between nanosecond lasers and Si is pivotal for advancing a wide range of technologies related to material processing and characterization. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Lab on a Chip," which focuses on devices and applications at the micro- and nanoscale. It includes information about the articles featured in the issue, as well as details about the journal's editorial staff and submission guidelines. The journal aims to publish significant and original work related to miniaturization and technological advancements in various fields. The article titled "Murakami Lab" is a scientific journal published by The Royal Society of Chemistry in 2023. The journal discusses a chip called "Chip 2023" developed by the Murakami Lab. The chip is described as having potential applications in various fields. The article provides specific details about the chip's features and capabilities. [Extracted from the article]

Although several lysis methods are available, biomedical applications are pushing the demand for miniaturised systems and thus for new ways to lyse cells in small volumes. In this work, we demonstrate in-droplet cell lysis of AC16 human cardiomyocyte cells in 20 μL droplets using high frequency surface acoustic waves. The acoustic streaming leads to high shear flow creating porous or breaking the cell membrane and releasing intracellular material. Contrary to previous work where the lysis efficiency is measured by a cell-permeant dye that can be used to determine cell viability, here we propose to quantify the DNA extracted from the cells as a measure of the lysis efficiency. This reagent-free method provides a valuable cell lysis alternative for many biological and biomedical applications, particularly for the development of point-of-care platforms. [ABSTRACT FROM AUTHOR]

Exhaled human breath analysis has great potential for the diagnosis of diseases in non-invasive way. The 13C-Urea breath test for the diagnosis of Helicobacter pylori infection indicates the ammonia concentration of 50–400 ppb in the breath. This work successfully developed a surface acoustic wave (SAW) resonator based on graphene/polypyrrole composite films decorated by gold nanoparticles (AuNPs–G/PPy) with sensitivity and selectivity to detect ammonia in parts-per-billion concentrations, which is promising for the accurate diagnosis of H. pylori infection. XRD, EDS, and SEM characterized the AuNPs–G/PPy nanocomposites, providing comprehensive insights into their structural, compositional, and morphological properties. The gas-sensing capabilities of the fabricated SAW sensors were extensively investigated, focusing on their response to NH3 gas at ambient temperature. The concentration of ammonia gas was effectively quantified by monitoring the frequency shift of the SAW device. Notably, our developed SAW sensor demonstrated outstanding sensitivity, selectivity, repeatability, and reproducibility for 50–1000 ppb NH3 in dry air. The excellent sensing performance of the AuNPs–G/PPy hybrid composite film can be attributed to the synergistic effects of graphene's superior conductivity, the catalytic properties of gold nanoparticles, and the conductivity sensitization facilitated by electron-hole recombination on the polypyrrole surface. [ABSTRACT FROM AUTHOR]

Surface acoustic wave (SAW) devices are promising for chemical and biological sensing applications. This work studies the basic operating principles and the physical behaviors of the "Rayleigh"-SAW and the "Shear Horizontal (SH-)" bulk acoustic wave (BAW), particularly in relation to the chemisorption process. A complete 3D delay line SAW model is developed and performed by the finite element analysis, and a methodology was introduced for characterizing the transmission characteristics (S21) of these devices. Notably, our investigation unveils an intriguing phenomenon in the behavior of SH-BAW in response to loading mass. We observed an anomalous shift in the central frequency, which increases as the chemical adsorbate concentration rises. Leveraging these insights, we designed and constructed a SAW-based gas sensor, and the vinyl-terminated polydimethylsiloxane was synthesized for the detection of chloroform, a challenging pollutant to identify. Through a comparative study, we illustrate distinct responses of Rayleigh-SAW and SH-BAW devices to accumulated loading mass and gaseous contaminants. These experimental results validate and corroborate our simulations. This work demonstrates a unique mass-loading effect exhibited by SH-BAW devices, which differs from the existing theories. These findings offer the opportunity to refine and enhance models for accurately describing the functionality of delay line SAW sensors, thereby contributing to improved sensor reliability. [ABSTRACT FROM AUTHOR]

Sonoporation refers to the formation of tiny transient pores in cell plasma membranes by using ultrasound to increase the permeability to bioactive materials. Recently, the Sonoporation technique has been widely researched in cell treatment applications, such as gene transfection. However, due to the random distribution of microbubbles, it is challenging to perform controllable and precise localized sonoporation of a target cell. In this work, a device based on the surface acoustic wave is developed to achieve a selective manipulation and cavitation of microbubbles. The device consists of a pair of microbubble positioning slant‐finger interdigital transducers (SFITs) for moving a selected microbubble in a two‐dimensional plane. Meanwhile, another narrow‐frequency‐band SFIT is integrated into the device for local cavitation control of the same microbubble. As a result, a microbubble can be transported orthogonal to and along the acoustic transmission path by continuously adjusting the input frequency and relative phase. Upon reaching the target cell, the selected microbubble can be cavitated without exciting other microbubbles, resulting in local sonoporation. The resolution of phase‐based positioning and frequency‐based transportation are 8.3 and 7.0 µm with 45° and 10 kHz settings, respectively. [ABSTRACT FROM AUTHOR]