Acoustic Wave Research Articles

Modeling Acoustic Attenuation, Sound Velocity and Wave Propagation in Lithium‐Ion Batteries via a Transfer Matrix

AbstractA simple 1D transfer matrix model of a battery is introduced and parametrized using harvested individual cell components at 0 % and 100 % SoC. This model allows for the calculation of group velocity and attenuation. The results of the model show good agreement with measured values, highlighting increased attenuation and group velocity at the resonances. This emphasizes the importance of selecting a suitable interrogation frequency for ultrasound investigations in lithium‐ion batteries. The model accurately replicates the observed weakening of resonances with increasing SoC. Additionally, it provides the basis to fit US spectroscopy data in the future, enabling immediate determination of component thickness and the Young's modulus of individual components, along with aiding in the identification aging effects of the anode and cathode materials. The model can visualize wave propagation within the battery. At certain frequencies, standing waves form which could be used in high‐intensity ultrasound applications targeted at individual cell components.

Effect of Regularized $$\kappa $$ Distribution and Polarization Force on the Dust Acoustic Waves in the Mesosphere Region

Effect of Regularized $$\kappa $$ Distribution and Polarization Force on the Dust Acoustic Waves in the Mesosphere Region

Acoustofluidic tweezers via ring resonance.

Ring resonator (RR) devices are closed-loop waveguides where waves circulate only at the resonant frequencies. They have been used in sensor technology and optical tweezers, but controlling micron-scale particles with optical RR tweezers is challenging due to insufficient force, short working distances, and photodamage. To overcome these obstacles, an acoustofluidic RR-based tweezing method is developed to manipulate micro-sized particles that can enhance particle trapping through the resonance interaction of acoustic waves with high Q factor (>3000), more than 20 times greater than traditional acoustic transducers. Particles can be precisely manipulated within the RR by adjusting the signal phase, with trapping amplified by enlarging the connected waveguide. Rapid particle mixing is achieved when particles are placed between the waveguide and RR. The signal path is strengthened by strategically positioning the RR in a two-dimensional plane. Acoustofluidic RR tweezers have immense potential for advancing applications in biosensing, mechanobiology, lab-on-a-chip, and cell-cell communication research.

First observational evidence of plasma waves in the martian magnetosheath jet

Abstract Mars Atmosphere and Volatile EvolutioN (MAVEN) mission reveals the existence of magnetosheath jets in the Martian plasma environment. The jets, which contrast with the surrounding plasma in the magnetosheath region, are transitory, locally limited plasma structures with high dynamic pressure. For the first time, MAVEN’s high-time resolution burst mode data are utilized to analyse plasma waves in these jets. Our investigation reveals the simultaneous presence of solitary waves, double layers, electron acoustic waves, and mirror modes. These waves in the Martian magnetosheath jets show similar wave characteristics to those observed in the Earth’s magnetosheath jets. These plasma wave observations will help us comprehend the genesis of jets in the Martian plasma environment as they are carriers of momentum and energy across different regions.

Near GHz Lithium Niobate Higher-Order Topological Nanomechanical Metamaterials.

Precise control over the localization of acoustic waves at microwave frequencies reveals new opportunities in emerging fields like quantum acoustics and spin mechanics. Conventional microwave acoustic resonators, engineered via phonon band structures, are prone to disturbances from fabrication defects, constraining their further development. Acoustic high-order topological insulators, known for their defect robustness and precise localization, have emerged as the preferred approach for developing high-performance resonators. However, the operating frequencies of existing acoustic high-order topological insulators have been limited to relatively low frequencies. Here, we present on-chip acoustic higher-order topological insulators (700-750 MHz) operating in the ultrahigh-frequency band, using lithium niobate nanomechanical metamaterials with smooth surfaces and sharp corners. By breaking the inversion symmetry of honeycomb lattices, higher-order valley Hall topological insulators featuring both odd-type and even-type corner states are constructed. Together, these advances promote the practical application of topological acoustics.

A novel gyroscope based on the slow surface acoustic wave in a phononic metamaterial.

Limited to the direct modulation on the surface acoustic wave (SAW) by the rotation, the conventional SAW gyroscopes incur weak Coriolis effects and gyroscopic effects. In this paper, we innovatively utilize a phononic metamaterial (PM) operated at whispering-gallery modes (WGMs) as the vehicle for the Coriolis effect rather than SAW itself. The gyroscopic effects of this PM are investigated, and a new SAW gyroscope is subsequently proposed based on the slow SAW in PM. We show, combining theoretical modeling and finite element method simulation, that the rate of rotation can linearly induce the splitting of WGMs and modulate the phase velocity of SAW down to 4600 m/s (initial phase velocity of 5355 m/s); the direction of rotation results in the chiral symmetry of the PM vibration and the asymmetric distribution of the transmissive SAW. Besides, the proposed SAW gyroscope measures the angular velocity by detecting the phase shift resulting from rotation-dependent slow SAW in PM, obtaining a sensitivity of 0.016 deg/Hz when 50-cell PM. Compared with the existing SAW gyroscopes based on phase velocity modulation, the gyroscopic gain factor in this paper is enhanced by 430-1600 times. This work jumps out of the framework of directly modulating SAW in gyroscopes and provides an innovative scheme of the indirect modulations from the rotation-dependent PM on SAW, showing excellent performance and potential for angular velocity measurement in extreme environments.

Strain-dependent magnon transport in CoFe2O4/NiO/CoFe2O4 junctions induced by bulk acoustic waves

Strain-dependent magnon transport in CoFe2O4/NiO/CoFe2O4 junctions induced by bulk acoustic waves

Perfusion Process Intensification for Lentivirus Production Using a Novel Scale-Down Model.

Process intensification has become an important strategy to lower production costs and increase manufacturing capacities for biopharmaceutical products. In particular for the production of viral vectors like lentiviruses (LVs), the transition from (fed-)batch to perfusion processes is a key strategy to meet the increasing demands for cell and gene therapy applications. However, perfusion processes are associated with higher medium consumption. Therefore, it is necessary to develop appropriate small-scale models to reduce development costs. In this work, we present the use of the acoustic wave separation technology in combination with the Ambr 250 high throughput bioreactor system for intensified perfusion process development using stable LV producer cells. The intensified perfusion process developed in the Ambr 250 model, performed at a harvest rate of 3 vessel volumes per day (VVD) and high cell densities, resulted in a 1.4-fold higher cell-specific functional virus yield and 2.8-fold higher volumetric virus yield compared to the control process at a harvest rate of 1 VVD. The findings were verified at bench scale after optimizing the bioreactor set-up, resulting in a 1.4-fold higher cell-specific functional virus yield and 3.1-fold higher volumetric virus yield.

A Laterally Excited Bulk Acoustic Wave Resonator Based on LiNbO3 with Arc-Shaped Electrodes

High frequency and large bandwidth are growing trends in communication radio-frequency devices. The LiNbO3 thin film material is expected to become the preferred piezoelectric material for high coupling resonators in the 5G frequency band due to its ultra-high piezoelectric coefficient and low loss characteristics. The main mode of laterally excited bulk acoustic wave resonators (XBAR) have an ultra-high sound velocity, which enables high-frequency applications. However, the interference of spurious modes is one of the main reasons hindering the widespread application of XBAR. In this paper, a Z-cut LiNbO3 thin film-based XBAR with arc-shaped electrodes is presented. We investigate the electric field distribution of the XBAR, while the irregular boundary of the arc-shaped electrodes affects the electric field between the existing interdigital transducers (IDTs). The mode shapes and impedance response of the XBAR with arc-shaped electrodes and the XBARs with traditional IDTs are compared in this work. The fabricated XBAR on a 350 nm Z-cut LiNbO3 thin film with arc-shaped electrodes operating at over 5 GHz achieves a high effective electromechanical coupling coefficient of 29.8% and the spurious modes are well suppressed. This work promotes an XBAR with an optimized electrode design to further achieve the desired performance.

Acoustofluidic Tweezers Integrated with Droplet Sensing Enable Multifunctional Closed-Loop Droplet Manipulation.

Droplet manipulation technologies with surface acoustic waves attract significant attention for applications in fluid handling and bioanalysis. However, existing technologies face challenges in automation, precision, and functional integration, limiting broader applications. In this work, a highly integrated droplet-sensing acoustofluidic tweezer is developed, incorporating orthogonally arranged slanted finger interdigital transducers and a custom-designed control and detection circuit system. Using a single acoustic device, this tweezer enables switchable acoustic droplet manipulation and detection, providing multifunctional closed-loop manipulation of on-chip microliter-scale droplets. The platform takes advantage of the wideband frequency response characteristics of the transducers, along with an automated droplet detection algorithm, enabling high-precision detection of central positions, edge positions, contact diameters, and the number of droplets. With this feedback, automated closed-loop control of various droplet manipulation functions, including transportation, merging, mixing, splitting, and internal particle enrichment, is achieved for the first time on a single acoustic platform. This significantly enhances the precision, efficiency, and fault tolerance of the manipulation process. This droplet-sensing acoustofluidic tweezer provides an innovative acoustic solution for droplet manipulation technologies in fields such as fluid processing and biosensing, demonstrating significant application potential.

Acoustic and acousto-optic properties of Ga10Ge15Te75 glass

The acoustic and acousto-optic (AO) properties of the Ga10Ge15Te75 glass, which is promising for creation of AO devices operating with the near and middle infrared optical radiation, are studied. In this paper, the experimental results for the longitudinal and shear acoustic waves phase velocities and the AO figure of merit (M2) in case of isotropic diffraction by these waves are presented. All measurements are carried out for the 3.39 µm optical wavelength. The obtained M2 magnitudes turned out to be close to 1000·10–15s3/kg that significantly exceeds the typical values observed in germanium (Ge) crystal – the basic material for middle infrared AO devices fabrication. The experimentally determined longitudinal acoustic wave attenuation coefficient for 100 MHz ultrasound frequency turns out to be 1.32 ± 0.05 cm-1. Finally, the acoustic and AO properties of telluride based glasses with the close chemical composition, namely Ga10Ge15Te75, Si25Te75 and Ge25Se15Te60 glasses, are compared.

An Effective Discontinuous Galerkin Method for Solving Acoustic Wave Equations in Heterogeneous Media

Abstract A discontinuous Galerkin (DG) method is introduced for solving 2D and 3D first-order velocity-pressure acoustic wave propagation problems in heterogeneous media. First, acoustic equations are reformulated into a first-order hyperbolic system, which can be integrated into the framework of the DG method. Then, we introduce an effective numerical flux in DG spatial discretization, which preserves physical laws on both sides of interfaces with discontinuous material parameters. It is compared with both the classic Lax-Friedrichs flux and the exact upwind flux, with the latter derived from solving the Riemann problem and satisfying the Rankine-Hugoniot condition. The comparison reveals that while our flux is formally similar to the classic local Lax-Friedrichs flux, its numerical behavior is analogous to the exact upwind flux. The primary advantage of this method lies in its simplicity and straightforward computation yet can maintain physical continuity conditions near interfaces with discontinuous material parameters. Several numerical experiments of acoustic wave propagation in 2D and 3D heterogeneous media are carried out, illustrating the effectiveness of this method.

High-Performance SAW-Based Microfluidic Actuators Composed of Sputtered Al–Cu IDT Electrodes

To realize highly sensitive SAW devices, novel Al–Cu thin films were developed using a combinatorial sputtering system. The Al–Cu sample library exhibited a wide range of chemical compositions and electrical resistivities, providing valuable insights for selecting optimal materials for SAW devices. Considering the significant influence of electrode resistivity and density on acoustic wave propagation, an Al–Cu film with 65 at% Al was selected as the IDT electrode material. The selected Al–Cu film demonstrated a resistivity of 6.0 × 10−5 Ω-cm and a density of 4.4 g/cm3, making it suitable for SAW-based microfluidic actuator applications. XRD analysis revealed that the Al–Cu film consisted of a physical mixture of Al and Cu without the formation of Al–Cu alloy phases. The film exhibited a fine-grained microstructure with an average crystallite size of 7.5 nm and surface roughness of approximately 6 nm. The SAW device fabricated with Al–Cu IDT electrodes exhibited excellent acoustic performance, resonating at 143 MHz without frequency shift and achieving an insertion loss of −13.68 dB and a FWHM of 0.41 dB. In contrast, the Au electrode-based SAW device showed significantly degraded acoustic characteristics. Moreover, the SAW-based microfluidic module equipped with optimized Al–Cu IDT electrodes successfully separated 5 μm polystyrene (PS) particles even at high flow rates, outperforming devices with Au IDT electrodes. This enhanced performance can be attributed to the improved resonance characteristics of the SAW device, which resulted in a stronger acoustic radiation force exerted on the PS particles.

Injection locking in DC-driven spintronic vortex oscillators via surface acoustic wave modulation

Control of the microwave signal generated by spin-transfer torque oscillators (STOs) is crucial for their applications in spin wave generation and neuromorphic computing. This study investigates injection locking of a DC-driven vortex STO using surface acoustic waves (SAWs) to enhance the STO’s signal and allow for its synchronization with external inputs. We employ a simplified model based on Thiele’s formalism and highlight the role of vortex deformations in achieving injection locking. Micromagnetic simulations are conducted to validate our theoretical predictions, revealing how the locking bandwidth depends on SAW amplitude, as well as on the amplitude and direction of an applied external field. Our findings are pivotal for advancing experimental research and developing efficient low-power synchronization methods for large-scale STO networks.

Emerging Trends in Integrated Digital Microfluidic Platforms for Next-Generation Immunoassays

Technologies based on digital microfluidics (DMF) have made significant advancements in the automated manipulation of microscale liquids and complex multistep processes. Due to their numerous benefits, such as automation, speed, cost-effectiveness, and minimal sample volume requirements, these systems are particularly well suited for immunoassays. In this review, an overview is provided of diverse DMF manipulation platforms and their applications in immunological analysis. Initially, droplet-driven DMF platforms based on electrowetting on dielectric (EWOD), magnetic manipulation, surface acoustic wave (SAW), and other related technologies are briefly introduced. The preparation of DMF is then described, including material selection, fabrication techniques and droplet generation. Subsequently, a comprehensive account of advancements in the integration of DMF with various immunoassay techniques is offered, encompassing colorimetric, direct chemiluminescence, enzymatic chemiluminescence, electrosensory, and other immunoassays. Ultimately, the potential challenges and future perspectives in this burgeoning field are delved into.

Analysis of Multivariable Sensor Responses to Multi-Analyte Gas Samples in the Presence of Interferents and Humidity.

This work presents an adaptive sensor signal-processing approach to enable quantification, using a single gas sensor or a small sensor array, of multianalyte mixtures of aromatic hydrocarbons in the presence of various interferents and humidity for environmental-monitoring applications. Dynamic sensor responses are analyzed by extracting multivariable sensing parameters to provide necessary sensitivity and selectivity. This is achieved by integrating the Levenberg-Marquardt-modified, exponentially weighted, recursive-least-squares-estimation (LM-modified EW-RLSE) algorithm and principal-component analysis (PCA). Achieving measured detection limits as low as 3 μg/L (≤1 ppm by volume) for 6 target analytes, the system exhibits excellent PCA cluster separation for all analytes in the mixtures, with reliable identification and accurate quantification, even in the presence of various interferents. Concentration errors of approximately ±5% are obtained for mixtures containing up to 6 BTEX compounds (including chemical isomers) and up to 4 interferents. Additionally, the study investigates the impact of humidity on the polymer/plasticizer-coated shear-horizontal surface acoustic wave (SH-SAW) sensors, demonstrating accurate concentration estimation in a relative humidity range from dry nitrogen to 65%. This sensing-and-multivariate-signal-processing approach is a promising candidate for reliable environmental monitoring in real-world applications.

A Sensitive Frequency Band Study for Distributed Acoustical Sensing Monitoring Based on the Coupled Simulation of Gas–Liquid Two-Phase Flow and Acoustic Processes

The sensitivity of gas and water phases to DAS acoustic frequency bands can be used to interpret the production profile of horizontal wells. DAS typically collects acoustic signals in the kilohertz range, presenting a key challenge in identifying the sensitive frequency bands of the gas and water phases in the production well for accurate interpretation. In this study, a gas–water two-phase flow–acoustic coupling model for a horizontal well is developed by integrating a gas–water separation flow model with a pipeline acoustic model. The model simulates the sound pressure level (SPL) and amplitude variations of acoustic waves under different flow patterns, spatial locations, and gas–water ratio schemes. The results demonstrate that within the same flow pattern, an increase in the gas–water ratio significantly elevates acoustic amplitude and SPL peaks within the 5–50 Hz frequency band. Analysis of oil field DAS data reveals that the amplitude response range for stages with a lower gas–water ratio falls within 5–10 Hz, whereas stages with a higher gas–water ratio exhibit an amplitude response range of 10–50 Hz.

The Peculiarities of Acoustic Normal Waves Propagation in Thin Porous Sheets of Thermally Expanded Graphite

Thermally expanded graphite belongs to a new class of graphite materials with unique physical, chemical and mechanical properties. Acoustic wave velocity is one of the most important characteristics for study of porous materials including thin porous sheets of thermally expanded graphite. In this paper peculiarities of symmetric mode S0 Lamb wave propagation and SH-wave with horizontal polarization in sheets of thermally expanded graphite are experimentally investigated. To determine their velocities a differential measurement scheme on the base of a low-frequency acoustic flaw detector DIO1000 LF and specialized piezoelectric transducers with dry point contact was used. Additionally the longitudinal wave velocity in direction of sheet thickness was determined using piezoelectric transducers based on polyvinylidene fluoride. Indicatrices of normal wave velocities in the rolling plane were plotted and it was shown that the maximum acoustic anisotropy is characteristic for the S0-mode. The velocity minimum corresponds to the longitudinal direction of the rolling plane in which the maximum elongation of gas pores was observed. Influence of thickness and density of thermally expanded graphite sheets on the velocities of normal waves was investigated and presence of the thickness range where the minimum velocity values were observed due to the maximum inhomogeneity of layers formed in the rolling process. Method for determination of dynamic elastic moduli of porous thermally expanded graphite sheets using experimentally measured velocities of normal waves was proposed. It was shown that in the longitudinal direction of the rolling plane the Poisson's ratio took negative values which allow to attribute the specified material to auxetics ones.

Behavior recognition algorithm based on a dual-stream residual convolutional neural network

Abstract In the process of behavior recognition, the recognition operation may be carried out in various environments such as sunny, cloudy, and night. Since traditional recognition algorithms are judged by identifying the pixels of the image, the intensity of the light will affect the image. The brightness and contrast of the display thus interfere with the recognition results. Therefore, traditional algorithms are easily affected by the lighting environment around the recognition object. To improve the accuracy and recognition rate of the behavior recognition algorithm in different lighting environments, a convolutional neural network (CNN) algorithm using a dual-stream method of time flow and spatial flow is studied here. First, we collect behavioral action data sets and preprocess the data. The core of the behavior recognition algorithm of the dual-stream residual CNN is to use the time stream and the spatial stream to fuse behavioral features and eliminate meaningless data features. After processing Perform feature selection on the data, select the acoustic wave and light-sensing features of the data, and finally, use the extracted features to classify and identify using the two-stream residual CNN and the traditional behavior recognition method. The behavior recognition algorithm based on the dual-stream residual CNN was tested on the data of four groups of people. For the behavioral feature map with a data volume of 50, the behavior recognition algorithm of the dual-stream residual CNN was effective in various environments under different lighting conditions. The recognition accuracy can reach 83.5%, which is 12.3% higher than the traditional. The behavior recognition algorithm of the dual-stream residual CNN takes 17.25 s less than the conventional recognition algorithm. It is concluded that behavior recognition based on dual-stream residual CNNs can indeed improve the recognition accuracy and recognition speed in environments with different lighting conditions than traditional behavior recognition.

Analysis of Influence of Excitation Source Direction on Sound Transmission Loss Simulation Based on Alloy Steel Phononic Crystal

As a type of locally resonant phononic crystal, alloy steel phononic crystals have achieved notable advancements in vibration and noise reduction, particularly in the realm of low-frequency noise. Their exceptional band gap characteristics enable the efficient reduction of vibration and noise at low frequencies. However, the conventional transmission loss (TL) simulation of finite structures remains the benchmark for plate structure TL experiments. In this context, the TL in the XY-direction of phononic crystal plate structures has been thoroughly investigated and analyzed. Given the complexity of sound wave incident directions in practical applications, the conventional TL simulation of finite structures often diverges from reality. Taking tungsten steel phononic crystals as an example, this paper introduces a novel finite element method (FEM) simulation approach for analyzing the TL of alloy steel phononic crystal plates. By setting the Z-direction as the excitation source, the tungsten steel phononic crystal plate exhibits distinct responses compared to excitation in the XY-direction. By combining energy band diagrams and modes, the impact of various excitation source directions on the TL simulations is analyzed. It is observed that the tungsten steel phononic crystal plate exhibits a more pronounced energy response under longitudinal excitation. The TL map excited in the Z-direction lacks the flat region present in the XY-direction TL map. Notably, the maximum TL in the Z-direction is 131.5 dB, which is significantly lower than the maximum TL of 298 dB in the XY-direction, with a more regular peak distribution. This indicates that the TL of alloy steel phononic crystals in the XY-direction is closely related to the acoustic wave propagation characteristics within the plate, whereas the TL in the Z-direction aligns more closely with practical sound insulation and noise reduction engineering applications. Therefore, future research on alloy steel phononic crystal plates should not be confined to the TL in the XY-direction. Further investigation and analysis of the TL in the Z-direction are necessary. This will provide a novel theoretical foundation and methodological guidance for future research on alloy steel phononic crystals, enhancing the completeness and systematicness of studies on alloy steel phononic crystal plates. Simultaneously, it will advance the engineering application of alloy steel phononic crystal plates.