Acoustic Wave Technology Research Articles

Effects of two kinds of surface acoustic wave disturbance systems on the synthesis of gold nanoparticles

In order to synthesize the gold nanoparticles (AuNPs) with uniform size and good morphology, two active disturbance systems based on surface acoustic wave (SAW) technology are presented and employed in the third stage (growth stage of crystal nuclei) of AuNPs liquid-phase synthesis. Through the optimization of SAW device, two kinds of SAW disturbance systems were designed and manufactured. For the orthogonal type SAW disturbance system, the concentration of synthesized AuNPs is the highest at Vpp = 5 V, but the size deviation of nanoparticles is a little larger. Meanwhile, for the rotary type SAW disturbance system, the concentration of synthesized AuNPs is significantly higher than the concentration of AuNPs synthesized in the orthogonal type SAW system. Moreover, the AuNPs synthesized by the rotary type SAW system are with more regular morphology and better monodispersity at Vpp = 35 V and f0 = 50 MHz. Therefore, rotary type SAW disturbance system has a better perturbation effect for the controllable synthesis of AuNPs.

Combining Mass Spectrometry, Surface Acoustic Wave Interaction Analysis, and Cell Viability Assays for Characterization of Shiga Toxin Subtypes of Pathogenic Escherichia coli Bacteria.

Shiga toxin (Stx)-producing Escherichia coli (STEC) and enterohemorrhagic E.coli (EHEC) as a human pathogenic subgroup of STEC are characterized by releasing Stx AB5-toxin as the major virulence factor. Worldwide disseminated EHEC strains cause sporadic infections and outbreaks in the human population and swine pathogenic STEC strains represent greatly feared pathogens in pig breeding and fattening plants. Among the various Stx subtypes, Stx1a and Stx2a are of eminent clinical importance in human infections being associated with life-threatening hemorrhagic colitis and hemolytic uremic syndrome, whereas Stx2e subtype is associated with porcine edema disease with a generalized fatal outcome for the animals. Binding toward the glycosphingolipid globotriaosylceramide (Gb3Cer) is a common feature of all Stx subtypes analyzed so far. Here, we report on the development of a matched strategy combining (i) miniaturized one-step affinity purification of native Stx subtypes from culture supernatant of bacterial wild-type strains using Gb3-functionalized magnetic beads, (ii) structural analysis and identification of Stx holotoxins by electrospray ionization ion mobility mass spectrometry (ESI MS), (iii) functional Stx-receptor real-time interaction analysis employing the surface acoustic wave (SAW) technology, and (iv) Vero cell culture assays for determining Stx-caused cytotoxic effects. Structural investigations revealed diagnostic tryptic peptide ions for purified Stx1a, Stx2a, and Stx2e, respectively, and functional analysis resulted in characteristic binding kinetics of each Stx subtype. Cytotoxicity studies revealed differing toxin-mediated cell damage ranked with Stx1a > Stx2a > Stx2e. Collectively, this matched procedure represents a promising clinical application for the characterization of life-endangering Stx subtypes at the protein level.

Acoustic tomography based on hybrid wave propagation model for tree decay detection

Acoustic wave technologies have been used in wood defect detection for many years. Various tomographic imaging algorithms have been proposed to construct two dimensional acoustic velocity maps that serve as the scientific evidence of tree’s internal condition. Many previously proposed algorithms were based on the assumption that acoustic waves propagate along straight rays in the cross sections of trees. To simulate the acoustic wave propagation more realistically, this paper proposed a tomographic imaging method based on a hybrid wave propagation model (HWPM) that includes two velocity inversion phases: straight-ray inversion and curved-ray inversion. The straight-ray inversion was first applied to obtain the preliminary velocity distribution, followed by the curved-ray inversion to refine the velocity distribution. A velocity correction factor was determined for each grid cell following each inversion iteration, and then was used to derive a new velocity value for each corresponding cell. The maximum and minimum velocity constraints were imposed on the newly-computed velocities, and some velocity constraints of grid cells were also imposed to address the nonuniqueness problem commonly existed in velocity inversion and generate a more accurate tomographic image. To evaluate the effectiveness of the hybrid inversion method, we conducted multipath acoustic wave testing on three short log sections (one sound and two with artificial defect) in the laboratory and four live trees in Yangzhou Slender West Lake Park, Jiangsu Province, China. Time-of-flight data was collected by PiCUS Tomograph tool and used to generate tomographic images with both Simultaneous iterative reconstruction technique (SIRT) and the proposed hybrid inversion method to make a comparison. Micro-drilling tests were conducted on the live trees to determine the internal condition and served as the basis for evaluating the tomographic images. Our results indicate that the hybrid wave propagation model is effective in constructing acoustic tomographic images that are reasonably accurate in detecting the internal defects of urban trees.

Finite Element Analysis of Laser-Generated Surface Acoustic Wave for Spinal Cord Tension Measurement

For patients with tethered cord syndrome (TCS), surgeons need accurate judgment of the tumor or bonding to be cut during the surgical procedures to release the spinal cord to normal tension. According to laser-generated surface acoustic wave (SAW) technology, using laser to irradiate the spinal cord with viscoelasticity to generate SAW, we can analyze the degree of traction in the spinal cord by the propagation conditions of SAW which is related to the physical and mechanical properties of the spinal cord surface. A finite element model was built in the environment of COMSOL Multiphasic. This simulation analyzed and verified the feasibility of laser-generated SAW technique for measuring spinal cord surface tension, and it will contribute to the development of the testing medical devices of spinal cord tension which enable doctors to achieve more accurate results during surgery.

A Novel Particulate Matter 2.5 Sensor Based on Surface Acoustic Wave Technology

Design, fabrication and experiments of a miniature particulate matter (PM) 2.5 sensor based on the surface acoustic wave (SAW) technology were proposed. The sensor contains a virtual impactor (VI) for particle separation, a thermophoretic precipitator (TP) for PM2.5 capture and a SAW sensor chip for PM2.5 mass detection. The separation performance of the VI was evaluated by using the finite element method (FEM) model and the PM2.5 deposition characteristic in the TP was obtained by analyzing the thermophoretic theory. Employing the coupling-of-modes (COM) model, a low loss and high-quality SAW resonator was designed. By virtue of the micro electro mechanical system (MEMS) technology and semiconductor technology, the SAW based PM2.5 sensor detecting probe was fabricated. Then, combining a dual-port SAW oscillator and an air sampler, the experimental platform was set up. Exposing the PM2.5 sensor to the polystyrene latex (PSL) particles in a chamber, the sensor performance was evaluated. The results show that by detecting the PSL particles with a certain diameter of 2 μm, the response of the SAW based PM2.5 sensor is linear, and in accordance with the response of the light scattering based PM2.5 monitor. The developed SAW based PM2.5 sensor has great potential for the application of airborne particle detection.

A Novel Rotation Speed Measurement Method Based on Surface Acoustic Wave

This paper presents an original passive wireless rotation speed measurement method based on surface acoustic wave (SAW) technology. A theoretical analysis was conducted on the principle of SAW rotation speed measurement and a numerical analysis on the SAW response energy pulses with different rotation angles and resonance frequencies was performed. Numerical calculation results showed that when the distance and the effective length of the antenna connected to SAWR vary with the rotation angle, the energy of acquired SAW response varies periodically. The rotation speed was estimated by searching the crossing points of the SAW response energy pulses and its mean value line. The SAW rotation speed measurement system was set up and the high performance SAW resonators were fabricated on a quartz substrate. The proposed measurement system was tested with a maximum error of 0.6 rpm, indicating that the system is capable of measuring rotation speeds from 10 to 100 rpm. Experimental results verified the validity and feasibility of presented rotation speed measurement method.

Coevaporation and structuring of titanium–aluminum alloy thin films

Intermetallic phases of binary material systems, such as TiAl, Ti3Al, RuAl, and Ni3Al have special physical properties such as a high oxidation resistance and low creep at high temperatures and a mechanical stability over wide temperature ranges. Due to new fields of application, such phases became increasingly important in the last two decades. In general, alloys can be sputtered very easily and reproducible. In surface acoustic wave (SAW) technology and microelectronics, the lift-off structuring technique is a fundamental process in the production of structured thin (<500 nm) metallic electrodes especially for low-cost fabrication of interdigital transducers (IDT). However, the structuring by standard lift-off technology only results in high quality IDTs for evaporated and not for sputtered layers. In order to investigate the intermetallic phases of the binary Ti-Al material system for IDT fabrication for SAW technology, a modified evaporator system for the simultaneous deposition of the low (Al) and the high (Ti) melting materials is presented.

Passive Downhole Pressure Sensor Based on Surface Acoustic Wave Technology.

A passive surface acoustic wave (SAW) pressure sensor was developed for real-time pressure monitoring in downhole application. The passive pressure sensor consists of a SAW resonator, which is attached to a circular metal diaphragm used as a pressure transducer. While the membrane deflects as a function of pressure applied, the frequency response changes due to the variation of the SAW propagation parameters. The sensitivity and linearity of the SAW pressure sensor were measured to be 8.3 kHz/bar and 0.999, respectively. The experimental results were validated with a hybrid analytical–numerical analysis. The good results combined with the robust design and packaging for harsh environment demonstrated it to be a promising sensor for industrial applications.

A SAW wireless sensor network platform for industrial predictive maintenance

Predictive maintenance predicts the system health, based on the current condition, and defines the needed maintenance activities accordingly. This way, the system is only taken out of service if direct evidence exists that deterioration has actually taken place. This increases maintenance efficiency and productivity on one hand, and decreases maintenance support costs and logistics footprints on the other. We propose a system based on wireless sensor network to monitor industrial systems in order to prevent faults and damages. The sensors use the surface acoustic wave technology with an architecture composed of an electronic interrogation device and a passive sensor (without energy at the transducer) which is powered by the radio frequency transmitted by the interrogation unit. The radio frequency link transfers energy to the sensor to perform its measurement and to transmit the result to the interrogation unit—or in a description closer to the implemented, characterize the cooperative target cross section characteristics to recover the physical quantity defining the transducer material properties. We use this sensing architecture to measure the temperature of industrial machine components and we evaluate the robustness of the method. This technology can be applied to other physical parameters to be monitored. Captured information is transmitted to the base station through multi-hop communications. We also treat interferences involved in both interrogator to interrogator and sensor to interrogator communications.

Multimode filter composed of single-mode surface acoustic wave/bulk acoustic wave resonators

This paper discusses the possibility of realizing multimode filters composed of multiple single-mode resonators by using radio frequency surface and bulk acoustic wave (SAW/BAW) technologies. First, the filter operation and design principle are given. It is shown that excellent filter characteristics are achievable by combining multiple single-mode resonators with identical capacitance ratios provided that their resonance frequencies and clamped capacitances are set properly. Next, the effect of balun performance is investigated. It is shown that the total filter performance is significantly degraded by balun imperfections such as the common-mode rejection. Then, two circuits are proposed to improve the common-mode rejection, and their effectiveness is demonstrated.

Validation of Acoustic Wave Induced Traumatic Brain Injury in Rats

Background: This study looked to validate the acoustic wave technology of the Storz-D-Actor that inflicted a consistent closed-head, traumatic brain injury (TBI) in rats. We studied a range of single pulse pressures administered to the rats and observed the resulting decline in motor skills and memory. Histology was observed to measure and confirm the injury insult. Methods: Four different acoustic wave pressures were studied using a single pulse: 0, 3.4, 4.2 and 5.0 bar (n = 10 rats per treatment group). The pulse was administered to the left frontal cortex. Rotarod tests were used to monitor the rats’ motor skills while the water maze test was used to monitor memory deficits. The rats were then sacrificed ten days post-treatment for histological analysis of TBI infarct size. Results: The behavioral tests showed that acoustic wave technology administered an effective insult causing significant decreases in motor abilities and memory. Histology showed dose-dependent damage to the cortex infarct areas only. Conclusions: This study illustrates that the Storz D-Actor effectively induces a repeatable TBI infarct, avoiding the invasive procedure of a craniotomy often used in TBI research.

Frequency-based detection of female Aedes mosquito using surface acoustic wave technology: Early prevention of dengue fever

The increasing cases of dengue fever (DF) and dengue hemorrhagic fever (DHF) in the last decade have been reported worldwide. These conditions have led to huge economic loses and health complications. At present, no direct cure for DF and no efficient device to control or detect the Aedes mosquitoes that cause DF are available. Therefore, the fabrication of a device will reduce the probability of get infection since it works as a warning system, to exterminate Aedes mosquitoes as soon as discovered, and to evacuate the location until it be treated. This paper is the first to report the detection of the female Aedes mosquito in human habitations using a surface acoustic wave (SAW) sensor. The feasibility of an acoustic-based device that records differences in signals and noise levels from different mosquito species has been demonstrated in instructing frequency differences to detect female mosquitoes. The SAW sensor response was investigated with simulated and real Aedes mosquito signals. Decreased resonant peak amplitude was obtained with different wingbeat frequencies. The S11 magnitude was reduced by 0.6dB and 1.25dB with female and male Aedes mosquitoes, respectively. Furthermore, the SAW sensor exhibited good sensitivity in low sound pressure environments between 40 and 55dB, making it suitable for use inside an average home.

SAW Sensors for Chemical Vapors and Gases.

Surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identify new opportunities and needs for additional research in this area moving into the future.

Surface Acoustic Wave Technology and Its Application

This paper introduces briefly the structures, specifications and applications of surface acoustic wave (SAW) sensors, as well as the progresses in the related studies. The SAW sensors include Rayleigh wave, shear horizontal acoustic plate wave, Love wave and Lamb wave sensors. The application fields are classified according to the functions into physical sensors and chemical/biological sensors; the former can be performed more easily, but the latter homes special functions and so needs to be studied in more details based on the practical conditions. The SAW sensors have very high sensitivity and wide applications due to the velocities and phase of SAW are sensitive to the parameter changes of environments.

The influence of barrier layers (SiO2, Al2O3, W) on the phase formation and stability of RuAl thin films on LGS and CTGS substrates for surface acoustic wave technology

In order to achieve a higher thermal stability of RuAl thin films on LGS (La3Ga5SiO14) and CTGS (Ca3TaGa3Si2O14) substrates and to prevent an oxidation with Oxygen originating from the substrates various barrier layers (SiO2, Al2O3, W) are tested. The RuAl-barrier films were annealed at 800 °C for 10 h under high vacuum conditions. An analysis of the phase formation as well as of changes in the chemical composition of the RuAl film and the substrate reveals a strong dependence of the quality of the RuAl film on the applied barrier layer. In the case of Al2O3 a reaction between RuAl and the substrates takes place. The application of W films is challenging because of the high stresses which are present in the layer stack. However, SiO2 films act successfully as diffusion barriers.

High frequency surface acoustic wave resonator-based sensor for particulate matter detection

This paper describes the characterization of high frequency Surface Acoustic Wave Resonator based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent SAWR sensitivity to be tailored to the size of particles, thus making these types of sensors good candidates for PM10, PM2.5 and ultrafine particle (UFP) sensing. Our initial characterisation demonstrated a typical SAWR frequency shift of 60Hz in response to a deposition of ca. 0.21ng of 0.75μm-sized gold particles (∼50 particles) on the sensor surface. Sensor responses to different sized particles, such as ∼30μm diameter silicon, gold (diameters of ∼0.75μm and ∼20μm), ∼8μm fine sugar, PTFE (∼1μm and ∼15μm), ∼4μm talcum powder, and ∼2μm molybdenum powder were evaluated, and an average mass sensitivity of 275Hz/ng was obtained. Based on the results obtained in this study we believe that acoustic wave technology has great potential for application in airborne particle detection. Moreover, acoustic resonator devices can be integrated with CMOS interface circuitry to obtain sensitive, robust, low-power and low-cost particle detectors for a variety of applications including outdoor environmental monitoring.

Molecularly Imprinted Polymer Integrated with a Surface Acoustic Wave Technique for Detection of Sulfamethizole.

The synergistic effect of combining molecular imprinting and surface acoustic wave (SAW) technologies for the selective and label-free detection of sulfamethizole as a model antibiotic in aqueous environment was demonstrated. A molecularly imprinted polymer (MIP) for sulfamethizole (SMZ) selective recognition was prepared in the form of a homogeneous thin film on the sensing surfaces of SAW chip by oxidative electropolymerization of m-phenylenediamine (mPD) in the presence of SMZ, acting as a template. Special attention was paid to the rational selection of the functional monomer using computational and spectroscopic approaches. SMZ template incorporation and its subsequent release from the polymer was supported by IR microscopic measurements. Precise control of the thicknesses of the SMZ-MIP and respective nonimprinted reference films (NIP) was achieved by correlating the electrical charge dosage during electrodeposition with spectroscopic ellipsometry measurements in order to ensure accurate interpretation of label-free responses originating from the MIP modified sensor. The fabricated SMZ-MIP films were characterized in terms of their binding affinity and selectivity toward the target by analyzing the binding kinetics recorded using the SAW system. The SMZ-MIPs had SMZ binding capacity approximately more than eight times higher than the respective NIP and were able to discriminate among structurally similar molecules, i.e., sulfanilamide and sulfadimethoxine. The presented approach for the facile integration of a sulfonamide antibiotic-sensing layer with SAW technology allowed observing the real-time binding events of the target molecule at nanomolar concentration levels and could be potentially suitable for cost-effective fabrication of a multianalyte chemosensor for analysis of hazardous pollutants in an aqueous environment.

Molecularly imprinted polymer film interfaced with Surface Acoustic Wave technology as a sensing platform for label-free protein detection

Molecularly imprinted polymer (MIP)-based synthetic receptors integrated with Surface Acoustic Wave (SAW) sensing platform were applied for the first time for label-free protein detection. The ultrathin polymeric films with surface imprints of immunoglobulin G (IgG-MIP) were fabricated onto the multiplexed SAW chips using an electrosynthesis approach. The films were characterized by analyzing the binding kinetics recorded by SAW system. It was revealed that the capability of IgG-MIP to specifically recognize the target protein was greatly influenced by the polymer film thickness that could be easily optimized by the amount of the electrical charge consumed during the electrodeposition. The thickness-optimized IgG-MIPs demonstrated imprinting factors towards IgG in the range of 2.8–4, while their recognition efficiencies were about 4 and 10 times lower toward the interfering proteins, IgA and HSA, respectively. Additionally, IgG-MIP preserved its capability to recognize selectively the template after up to four regeneration cycles. The presented approach of the facile integration of the protein-MIP sensing layer with SAW technology allowed observing the real-time binding events of the target protein at relevant sensitivity levels and can be potentially suitable for cost effective fabrication of a biosensor for analysis of biological samples in multiplexed manner.

Simulation study and guidelines to generate Laser-induced Surface Acoustic Waves for human skin feature detection

Abstract Despite the seriously increasing number of people contracting skin cancer every year, limited attention has been given to the investigation of human skin tissues. To this regard, Laser-induced Surface Acoustic Wave (LSAW) technology, with its accurate, non-invasive and rapid testing characteristics, has recently shown promising results in biological and biomedical tissues. In order to improve the measurement accuracy and efficiency of detecting important features in highly opaque and soft surfaces such as human skin, this paper identifies the most important parameters of a pulse laser source, as well as provides practical guidelines to recommended proper ranges to generate Surface Acoustic Waves (SAWs) for characterization purposes. Considering that melanoma is a serious type of skin cancer, we conducted a finite element simulation-based research on the generation and propagation of surface waves in human skin containing a melanoma-like feature, determine best pulse laser parameter ranges of variation, simulation mesh size and time step, working bandwidth, and minimal size of detectable melanoma.

Effect of initial stress on propagation behaviors of shear horizontal waves in piezoelectric/piezomagnetic layered cylinders

An analytical approach is taken to investigate shear horizontal wave (SH wave) propagation in layered cylinder with initial stress, where a piezomagnetic (PM) material thin layer is bonded to a piezoelectric (PE) cylinder. Two different material combinations are taken into account, and the phase velocities of the SH waves are numerically calculated for the magnetically open and short cases, respectively. It is found that the initial stress, the thickness ratio and the material performance have a great influence on the phase velocity. The results obtained in this paper can offer fundamental significance to the application of PE/PM composite media or structure for the acoustic wave and microwave technologies.