Use Of Surface Acoustic Waves Research Articles

Pulsed surface acoustic waves accelerate wound healing and reveal new parameter limits for cell stimulation in vitro

The use of surface acoustic waves (SAW) in cell biology has gained high attention in the past years. Previous works show that SAW treatment of artificial wounds in vitro can accelerate wound healing by up to +135%. However, little is known about the mechanobiology behind these effects, and a stimulation has only been proven for continuous SAW signals so far. We here show that the stimulation efficacy observed in previous studies is preserved for pulsed stimuli applied to Madin-Darby canine kidney (MDCK-II) cells in wound healing assays on SAW chips at a resonance frequency f SAW = 160 MHz. Moreover, for a reproducible and reliable image analysis, we present the SegFormer-based deep learning algorithm Neural Cell Edge Detector for the cell edge segmentation and image binarization, that allows an automated determination of the stimulation efficacy. With these tools, we explore a wider range of applicable SAW intensities up to P in = 21 dBm (128 mW) with a maximum stimulation efficacy of E = 201%. We show that the order of magnitude of the stimulation effect is reproducible under the variation of SAW signal characteristics power P in, duty cycle D and pulse width τ, while the mean energy over time is constant. Below a distinct pulse duration limit τ = 100 ms, no direct stimulation effect was observed. From a mechanobiological point of view, these findings and time scales could narrow down the potentially triggered cellular mechanisms during the stimulation.

Deicing of Sessile Droplets Using Surface Acoustic Waves.

Deicing has significant relevance in various applications such as transportation, energy production, and telecommunication. The use of surface acoustic waves (SAWs) is an attractive option for deicing as it offers several advantages such as localized heating, in situ control, low power, and system integration for highly efficient deicing. Here, we report an understanding of the dynamics of deicing of microlitre volume water droplets (1 to 30 μL) exposed to low power (0.3 W) SAW actuation using an interdigitated electrode on a piezoelectric (LiNbO3) substrate. We study the time variation of the volume of liquid water from the onset of SAW actuation to complete deicing, which takes 2.5 to 35 s depending on the droplet volume. The deicing phenomenon is attributed to acoustothermal heating which is found to be greatly influenced by the loss of ice adhesion with the substrate and the acoustic streaming within the liquid water. Acoustothermal heating inside the droplet is characterized by the temperature distribution inside the droplet using infrared thermography, and acoustic streaming is observed using dye-based optical microscopy. A rapid enhancement in deicing is observed upon the detachment of ice from the substrate and the onset of acoustic streaming, marked by a sudden increase in the liquid water volume, droplet temperature, and heat transfer coefficient. The deicing time is found to increase linearly with droplet volume as observed from experiments and further verified using a theoretical model. Our study provides an improved understanding of the recently introduced SAW-based deicing technique that may open up the avenue for a suitable alternative to standard deicing protocols.

Use of Surface Acoustic Waves for Crack Detection on Railway Track Components—Laboratory Tests

The present work investigates the technical feasibility of a condition monitoring setup aiming at the detection of gauge corner cracks (aka head checks) in pearlitic railway rails, using a wayside (i.e., stationary) setup with surface acoustic waves (SAW) as its detection principle. The experimental SAW setup consists of a pitch-catch setup using piezo transducers equipped with comb adaptors to excite and measure narrowband Rayleigh waves with a center frequency of 1 MHz. SAW experiments were performed on a rail subjected to cyclic loading in a 1:1 wheel–rail test rig yielding the specific rolling contact fatigue, i.e., head checks. Elastodynamic finite integration technique (EFIT) simulations were performed to analyze the surface and bulk wave propagation in the rail and to predict the signals at specific receiver positions. SAW transmission and reflection scenarios at cracks were analyzed numerically via modelled variations of gauge corner crack configurations according to number of cracks (0–3) and depth (0, 0.5 mm and 1 mm). The numerical and the experimental results each show a clear correlation between the appearance and intensity of head check damage and the wave attenuation in transmission mode.

Enhanced acoustofluidic mixing in a semicircular microchannel using plate mode coupling in a surface acoustic wave device

In this study, we present enhanced acoustic mixing inside a semicircular microfluidic channel via acoustic streaming induced by acoustic plate modes (APMs) of a 500-μm-thick double-side polished lithium-niobate (LiNbO3) substrate. We demonstrated that the APMs supported by the LiNbO3 substrate can be excited by an interdigitated transducer (IDT) at higher frequencies, in addition to conventional surface acoustic waves (SAWs), and can generate stronger acoustic streaming flow (ASF) and stirring effects. Consequently, rapid and enhanced mixing processes were observed in the channel. We conducted full-wave modeling of the device with finite element (FE) simulation to elucidate the acoustic process and mixing behaviors of the APM-based approach. Subsequently, we fabricated the acoustofluidic device using a standard photolithographic process and a 3D-printed replica molding method. The measured excitation spectrum of SAW and APM agrees with the numerical prediction; additionally, experiments on mixing and 2 µm particle motion in the continuous channel flow validate the ability of the device to enhance micromixing using APM frequencies compared with that using SAWs in our device. Our approach enables distinctive APMs to be fully coupled to the SAW-based acoustofluidic platform, which potentially enables an integrated design for the use of SAW and APM frequencies, acoustic energy, and wave fields in a single system. Our results also suggest innovative applications of the conventional SAW acoustofluidic devices to extended frequency regimes via APMs without reducing the substrate thickness and IDT pitch.

The use of surface acoustic waves to evaluate of the near-surface layers of metal processed shot peening

1. Berezhnyts'ka MP, Kyrylenko SM, Paustovskii AV. Evaluation of residual stresses in bars subjected to surface hardening. Material Science. 1997;33(6): 851-861. https://doi.org/10.1007/BF0235.... CrossRef Google Scholar

Comb Filter Saw-Resonator Traveling Wave

Owing to the use of surface acoustic waves, the frequency range of this type of filter is expanded to the high frequency range and can reach several gigahertz. To implement filters on surface waves, piezoelectrics like a quartz plate are used. However, quartz is rarely used for the manufacture of broadband filters. Barium titanate or lithium niobate is commonly used.The difference in the operation of SAW filters from quartz or piezoceramic filters is that not a volumetric oscillation of the piezoelectric is used, but a wave propagating over the surface. In order to prevent body waves that could distort the frequency response, special constructive measures are taken. Most of the advantages of SAW devices are directly related to their physical structure: low weight and dimensions; linear (or defined by requirements) phase; shape factor approaching unity (very high squareness); exceptional out-of-band suppression; temperature stability. Since the center frequency and the shape of the frequency response are determined by the topology, they do not require complex settings in the equipment and cannot be upset during operation. Manufacturing technology compatible with semiconductor manufacturing allows them to be produced in large volumes with high reproducibility. Filtering devices on distributed components are considered. Since narrow band filters are constructed on surface - acoustic waves, there are difficulties in providing the vertex of the amplitude - frequency characteristic uniformity. When designing and creating new high-frequency electronics components, there is a need to reduce filter losses and harmonization. Offered the design and mathematical model of a comb filter based on a ring resonator of surface - acoustic waves and two waveguides on surface - acoustic waves, which are connected to a ring resonator at opposite points taking into account integral losses. This model helps to consider and calculate the propagation of waves inside the annular resonator in the light of losses. A topological scheme is described, which is described by the distribution of the energy of the signal and the coefficients of division. The division coefficients are represented as mathematical relations. The solutions of the amplitude and phase expressions by the method of successive approximations are presented. Reducing the loss in the filter and reducing the effect of the partition coefficient lead to an increase in the figure of merit of the ring resonator, which allows to take this into account when designing, since the characteristic moves to the range of higher damping values. We get a result that significantly reduces the bandwidth attenuation of the filter due to the loss reduction. The result obtained is described in the form of a linear circuit with feedback. The obtained characteristics are inherent in the comb filters, and the result is explained by the fact that the investigated structure is presented in the form of a linear circuit with delay and feedback. Also, it can be concluded that the advantages of the SAW are light weight and dimensions, temperature stability and relative ease of design and manufacture.

Dipole states and coherent interaction in surface-acoustic-wave\xa0coupled phononic resonators

Manipulation of mechanical motion at the micro-scale has been attracting continuous attention, leading to the successful implementation of various strategies with potential impact on classical and quantum information processing. We propose an approach based on the interplay between a pair of localised mechanical resonators and travelling surface acoustic waves (SAW). We demonstrate the existence of a two-sided interaction, allowing the use of SAW to trigger and control the resonator oscillation, and to manipulate the elastic energy distribution on the substrate through resonator coupling. Observation of the vectorial structure of the resonator motion reveals the existence of two coupling regimes, a dipole-dipole-like interaction at small separation distance versus a surface-mediated mechanical coupling at larger separation. These results illustrate the potential of this platform for coherent control of mechanical vibration at a resonator level, and reciprocally for manipulating SAW propagation using sub-wavelength elements.

Measurement of coherent surface acoustic wave attenuation in polycrystalline aluminum

Attenuation of Rayleigh-type surface acoustic waves induced by grain-boundary scattering is studied experimentally and theoretically by an effective medium approach. A frequency domain opto-acoustic laboratory setup, capable of measuring a coherent Rayleigh wave response by emulating an ensemble average via spatial averaging, is presented. Measurements are conducted on polycrystalline aluminum at ultrasonic frequencies from 10 MHz to 130 MHz. A constant effective phase velocity of 2893 m s−1 is found below 80 MHz. The effective attenuation coefficient varies in the whole frequency range by nearly two orders of magnitude, and shows classical scattering behavior, comprising stochastic and geometric scattering regimes. A semi-analytical attenuation model is presented, valid below the geometric limit. The model incorporates the material’s spatial two-point correlation function obtained from metallurgical micrographs. Comparisons to experimentally obtained attenuation coefficients show good quantitative agreement, with differences in the frequency power-law dependence. This study attempts to elucidate microstructure induced surface acoustic wave attenuation experimentally by means of a statistical approach. The proposed method and the obtained findings contribute to the understanding of wave propagation in heterogeneous media, and promote the use of surface acoustic waves in non-destructive microstructure characterization.

Delivery of femtolitre droplets using surface acoustic wave based atomisation for cryo-EM grid preparation.

Cryo-Electron Microscopy (cryo-EM) has become an invaluable tool for structural biology. Over the past decade, the advent of direct electron detectors and automated data acquisition has established cryo-EM as a central method in structural biology. However, challenges remain in the reliable and efficient preparation of samples in a manner which is compatible with high time resolution. The delivery of sample onto the grid is recognized as a critical step in the workflow as it is a source of variability and loss of material due to the blotting which is usually required. Here, we present a method for sample delivery and plunge freezing based on the use of Surface Acoustic Waves to deploy 6-8 µm droplets to the EM grid. This method minimises the sample dead volume and ensures vitrification within 52.6 ms from the moment the sample leaves the microfluidics chip. We demonstrate a working protocol to minimize the atomised volume and apply it to plunge freeze three different samples and provide proof that no damage occurs due to the interaction between the sample and the acoustic waves.

Current Flow in the Bubble and Stripe Phases.

The spontaneous ordering of spins and charges in geometric patterns is currently under scrutiny in a number of different material systems. A topic of particular interest is the interaction of such ordered phases with itinerant electrons driven by an externally imposed current. It not only provides important information on the charge ordering itself but potentially also allows manipulating the shape and symmetry of the underlying pattern if current flow is strong enough. Unfortunately, conventional transport methods probing the macroscopic resistance suffer from the fact that the voltage drop along the sample edges provides only indirect information on the bulk properties because a complex current distribution is elicited by the inhomogeneous ground state. Here, we promote the use of surface acoustic waves to study these broken-symmetry phases and specifically address the bubble and stripe phases emerging in high-quality two-dimensional electron systems in GaAs/AlGaAs heterostructures as prototypical examples. When driving a unidirectional current, we find a surprising discrepancy between the sound propagation probing the bulk of the sample and the voltage drop along the sample edges. Our results prove that the current-induced modifications observed in resistive transport measurements are in fact a local phenomenon only, leaving the majority of the sample unaltered. More generally, our findings shed new light on the extent to which these ordered electron phases are impacted by an external current and underline the intrinsic advantages of acoustic measurements for the study of such inhomogeneous phases.

Smart Cell Culture Systems: Integration of Sensors and Actuators into Microphysiological Systems.

Technological advances in microfabrication techniques in combination with organotypic cell and tissue models have enabled the realization of microphysiological systems capable of recapitulating aspects of human physiology in vitro with great fidelity. Concurrently, a number of analysis techniques has been developed to probe and characterize these model systems. However, many assays are still performed off-line, which severely compromises the possibility of obtaining real-time information from the samples under examination, and which also limits the use of these platforms in high-throughput analysis. In this review, we focus on sensing and actuation schemes that have already been established or offer great potential to provide in situ detection or manipulation of relevant cell or tissue samples in microphysiological platforms. We will first describe methods that can be integrated in a straightforward way and that offer potential multiplexing and/or parallelization of sensing and actuation functions. These methods include electrical impedance spectroscopy, electrochemical biosensors, and the use of surface acoustic waves for manipulation and analysis of cells, tissue, and multicellular organisms. In the second part, we will describe two sensor approaches based on surface-plasmon resonance and mechanical resonators that have recently provided new characterization features for biological samples, although technological limitations for use in high-throughput applications still exist.

Enhancement of plant leaf transpiration with effective use of surface acoustic waves: effect of wave frequency.

Water transport in vascular plants provides remarkable opportunities for various engineering applications due to its highly efficient and powerless transportability. Several previous studies were conducted to regulate the biological responses of plants using noninvasive audible or ultrasound waves. However, the control mechanism of acoustic stimuli applied to plants has not been investigated yet. Thus, the practical application of these stimuli to real plants still exhibits technological limitations. This study experimentally investigated the effects of surface acoustic wave (SAW) frequency on plant transpiration to understand the acoustic-activated leaf transpiration and utilize the advantages of SAW. We captured consecutive images of the enhanced water transport in the test plant (Epipremnum aureum) by SAW at three different frequencies (10, 15, and 20 MHz). The dye solution at 15 MHz SAW presented the highest intensity value after 40 min of SAW stimulation. The excitation areas for 15 and 20 MHz SAWs were decreased to 42.3% and 22.6%, respectively, compared with that of 10 MHz SAW. The transpiration rates were directly measured to compare water transport enhancement quantitatively when different SAW frequencies were applied to the same plant leaves. The water transport in the leaves was maximized at 15 MHz SAW, regardless of excitation area.

Методы обработки и регистрации биосигналов для задач медицинской диагностики

In radio engineering signal processing methods are widely used including spectral, correlation, wavelet analyses, etc. These methods are effectively used in processing the biosignals of a human organism for medical diagnostic purposes. Methods for analyzing and producing electromagnetic and acoustic fields in various media and systems are also commonly used. These methods are promising and useful also in studying a human organism. The article presents the main results from the research work carried out by the staff of the MPEI National Research University’s Chair of Radio Engineering Fundamentals aimed at development and use of radio engineering methods in the field of processing and recording biosignals for medical diagnostic purposes. The article outlines the works on studying the heart electric field in electrocardiology devoted to reconstructing an equivalent electric heart generator from the signals recorded by multichannel electrocardiographic leads and coordinates of electrodes placed on the human trunk surface. The results from studying the human trunk inhomogeneous model in terms of the effect the chest internal inhomogeneities have on the distribution of surface potentials are presented. Matters concerned with separation of biorhythm signals are considered under the conditions when the organism vital activity signals are simultaneously generated by several quasi-periodic processes, with the signal of interest weakly manifesting itself. A methodology for assessing the level of emotional stress by conducting a cross-correlation analysis of heart and respiration rhythms is described. Matters concerned with constructing and analyzing the characteristics of temperature sensors implanted in the body with the use of surface acoustic waves are discussed.

Measuring transducer of angular displacements using phase raids of the surface acoustic waves electric field

The phase method for angular displacement unambiguous measurement based on the use of surface acoustic waves (SAW) devices is proposed and theoretically grounded.To eliminate any ambiguity of phase measurements, the construction of acousto-electronic angular displacement transducer using phase incursion of several SAW on the surface of the piezoelectric circular waveguide at different frequencies is proposed. The information parameters that determine the position of SAW receiver are measured at these frequencies.The rating of potential metrological parameters of the 3-frequency angular displacement transducer in the range 0…..360 degrees with the formation of precise, intermediate and rough measurement scales is carried out. The use of phase incursion on the surface of the piezoelectric waveguide electric field of three SAW at different frequencies taking by moving SAW receiver allows to form precise, intermediate and rough measurement scales in accordance with 11, 6 and 5 binary digits representing the measurement results.The experimental test results of models of a 3-frequency generator block, an amplifying-selective block and a 3-frequencies angular displacement transducer containing circular piezoelectric waveguide with a radius of 15 mm based on zinc oxide-fused quartz structure over which displaces a circular sectional SAW receiver are presented. The amplitude of the SAW receiver output signal varies exponentially depending on a gap between the piezoelectric waveguide surface and SAW receiver. It requires high precision of transducer manufacturing to ensure parallel to the acoustic line surface movement of receiver thus eliminating the influence of the phase velocity dispersion of the surface acoustic wave as a result of the SAW receiver electric field perturbation on the accuracy of measurements. Grading characteristics of angular displacement transducer are linear. The coefficients of angular displacement transformation on the precise scales are 0.54, 0.55 and 0.56 electric degrees/arcsec in the central frequencies of 69.52, 70.62 and 71.69 MHz. At the same time, the resolution and angular displacements measurement error on the precise scale are respectively less than 0.5 arcsec and 1.5 arcsec.The test results of model based on piezoelectric waveguide of zinc oxide-fused quartz structure confirm the possibility of creating highly sensitive angular displacements transducers with a resolution and accuracy properties that are close to the parameters of inductosyns, photoelectric transducers and laser interferometers. However, it may have considerably less weight and dimensions, cost and complexity of construction.Ref. 20, fig.6.

Chemical-free lysis and fractionation of cells by use of surface acoustic waves for sensitive protein assays.

We exploit the mechanical action of surface acoustic waves (SAW) to differentially lyse human cancer cells in a chemical-free manner. The extent to which cells were disrupted is reported for a range of SAW parameters, and we show that the presence of 10 μm polystyrene beads is required to fully rupture cells and their nuclei. We show that SAW is capable of subcellular fractionation through the chemical-free isolation of nuclei from whole cells. The concentration of protein was assessed in lysates with a sensitive microfluidic antibody capture (MAC) chip. An antibody-based sandwich assay in a microfluidic microarray format was used to detect unlabeled human tumor suppressor protein p53 in crude lysates, without any purification step, with single-molecule resolution. The results are digital, enabling sensitive quantification of proteins with a dynamic range >4 orders of magnitude. For the conditions used, the efficiency of SAW-induced mechanical lysis was determined to be 12.9% ± 0.7% of that for conventional detergent-based lysis in yielding detectable protein. A range of possible loss mechanisms that could lead to the drop in protein yield are discussed. Our results show that the methods described here are amenable to an integrated point-of-care device for the assessment of tumor protein expression in fine needle aspirate biopsies.

Ultrasonically assisted deposition of colloidal crystals

Colloidal particles are a versatile physical system which have found uses across a range of applications such as the simulation of crystal kinetics, etch masks for fabrication, and the formation of photonic band-gap structures. Utilization of colloidal particles often requires a means to produce highly ordered, periodic structures. One approach is the use of surface acoustic waves (SAWs) to direct the self-assembly of colloidal particles. Previous demonstrations using standing SAWs were shown to be limited in terms of crystal size and dimensionality. Here, we report a technique to improve the spatial alignment of colloidal particles using traveling SAWs. Through control of the radio frequency power, which drives the SAW, we demonstrate enhanced quality and dimensionality of the crystal growth. We show that this technique can be applied to a range of particle sizes in the μm-regime and may hold potential for particles in the sub-μm-regime.

Surface acoustic waves in the testing of layered media. The waves’ sensitivity to variations in the properties of the individual layers

Research on the use of surface acoustic waves for the nondestructive testing of layered media is reviewed. A model to describe horizontally polarized surface acoustic waves in layered anisotropic (monoclinic) media is constructed. A modified transfer-matrix method is developed to obtain a solution. Non-canonical type waves with horizontal transverse polarization are investigated. Dispersion curves are constructed for a multilayer composite in contact with an anisotropic half-space. It is shown that the variation of the physical characteristics and the geometry of any of the internal layers leads to a variation in the dispersion curves. This opens up the possibility of using dispersion analysis for the nondestructive testing of the properties of the individual layers.

Evaluating surface hardened steels by laser-acoustics

The use of surface acoustic waves was studied as a means of evaluating surface-hardened steels. Four different grades of steel, 42CrMo4, C45, X153CrMoV12.1 and 90MnCrV8, were laser hardened up to a depth of 1.5 mm. The construction of a laser acoustic handheld probe enabled the measurement of the propagation velocity of the surface acoustic waves on large components. The measurement yields the velocity of the surface acoustic wave depending on frequency in a range from 1 to 10 MHz. The varying frequency enables the surface acoustic waves to penetrate varying depth of the material. It was investigated, if the hardening depth and the surface hardness can be deduced from this measurement. This methodology rests on the assumption that the velocity of the acoustic wave varies, if the microstructure of the steel is hardened by a martensitic transformation. Test samples were also annealed up to 620 °C to vary the hardness of the laser hardened zone. This was performed to investigate if the acoustic wave velocity correlates with the hardness. The sensitivity of the acoustic method, which can be used to determine the hardening depth and the hardness, depends on two aspects: 1. the amount of the effect of the martensitic hardening on the wave velocity of the steel and 2. the accuracy of the velocity that can be measured. A generalized dispersion curve was calculated using the theory of the surface acoustic wave to deduce the hardening depth from the velocity. Establishing this curve requires two measurements; the measurement of the wave velocities in the hardened and non-hardened steel. Using this methodology, it was found that the hardening depth could be determined with an error not higher than 15%.

Use of surface acoustic waves to reduce pain and discomfort related to indwelling nasogastric tube

Nasogastric intubation, one of the most widely utilized therapeutic procedures in medical practice, is associated with trauma, pain, and discomfort, which can occur both at insertion and during the indwelling phase. Although lubricating jelly is useful during the insertion phase, insertion can still cause great discomfort. Furthermore, the jelly is rapidly absorbed and therefore is unable to decrease the friction between the tissues and the tube during the indwelling phase of the nasogastric tube. The aim of this study was to test a device, the NG-Shield, that generates surface acoustic waves on the surfaces of the nasogastric tube to reduce contact time and thus friction between the nasogastric tube and body tissues. Twenty-four healthy volunteers were enrolled in a single-center, crossover, blinded study, in which a nasogastric tube was inserted and left indwelling for 6 hours. Throughout the indwelling period the device was activated and deactivated alternately every hour, and the volunteers were questioned every hour about their pain and discomfort levels as well as grading pain and discomfort upon insertion and removal of the nasogastric tube. Pain and discomfort levels were compared between active and nonactive phases of the device. The activated NG-Shield was found to reduce both pain and discomfort significantly in both the nose and throat throughout the indwelling phase. The NG-Shield is a safe and effective device for reducing pain and discomfort associated with an indwelling nasogastric tube.

Experimental research of non-uniformly quenched steel using surface acoustic waves

In the work results of research of sound velocity and attenuation of non-uniformly quenched high carbon steel are presented. Measurements were made by point source/point receiver technique with use of surface acoustic waves on frequency of 4.75 MHz. Features of behavior of sound velocity and attenuation in the quenching field was found. Correlation between sound velocity and attenuation and microhardness and phase composition of the sample was established. Work supported by RFBR.