RNA-peptide binding and the effect of inhibitor and RNA mutation studied by on-line acoustic wave sensor

Acoustic wave devices of the transverse shear-wave type are becoming increasingly important in the study of biochemical binding events at the solid-liquid interface in real time. The operation of the sensor is based on the principle that perturbations occurring at the solid-liquid interface result in changes in the propagating characteristics of the acoustic wave. The binding of the human immunodeficiency virus-type 1 Tat protein to the transactivation-responsive RNA element has been studied using this sensor. Variable acoustic signals in terms of frequency and motional resistance changes are obtained when surface-immobilized RNA is challenged by different peptide fragments derived from Tat protein. The effect of peptide concentration and mutation in addition to the inhibition of RNA-peptide binding by neomycin has been investigated. The results of this study suggest that acoustic physics offers considerable potential for the screening of small-molecule interactions with nucleic acids.     

Adsorptions of plasma proteins and their elutabilities from a polysiloxane surface studied by an on-line acoustic wave sensor

Gold electrodes of thickness-shear mode acoustic wave sensors were modified with poly[(mercaptopropyl)methylsiloxane]. The flow-through adsorption of three major plasma proteins (human serum albumin, fibrinogen, and immunoglobulin G) was detected by acoustic network analysis. The elution of fibrinogen and albumin from coated and unmodified gold surfaces by sodium dodecyl sulfate was studied with respect to different adsorption times and protein concentrations. Both sequential and competitive adsorptions of the three proteins on polymer-modified surfaces of sensors were examined as were simultaneous adsorptions from binary and ternary mixtures. The experimental results confirm that the competitive behaviors of proteins in terms of adsorptive processes are explained by factors other than displacement phenomena.     

Emission of a surface acoustic wave by an internal acoustic wave propagating near the surface

It was observed that the propagation of an internal acoustic wave near a surface is accompanied by the excitation of a surface acoustic wave directed at an angle to the internal wave. Pis’ma Zh. Tekh. Fiz. 24, 57–61 (September 26, 1998)     

基于ZnO半导体纳米线膜的声表面波型紫外探测器

针对传统半导体光电探测器件结构的宽带隙半导体紫外探测器可测信号弱的问题,提出了一种基于ZnO纳米线膜的声表面波型紫外探测器.该探测器利用ZnO纳米线膜的强紫外光电响应特性和声表面波器件的灵敏的声电相互作用机制,将采用高纯锌粉的热蒸发氧化工艺制备的纤锌矿型ZnO纳米线制作在已有声表面波小波传感器上.利用光致发光谱研究发现,由于低维激子限域效应和表面效应,所制作ZnO纳米线敏感膜中的紫外光电效应优于外延ZnO半导体薄膜;同时,基于ZnO纳米线膜的声表面波式紫外探测器在紫外光辐照下该探测器的中心频率减小,损耗增大.实验研究表明该器件能够实现长波紫外光的高灵敏度探测.     

Characteristics of MgxZn1-xO thin film bulk acoustic wave devices

Piezoelectric thin film zinc oxide (ZnO) and its ternary alloy magnesium zinc oxide (Mg/sub x/Zn/sub 1-x/O) have broad applications in transducers, resonators, and filters. In this work, we present a new bulk acoustic wave (BAW) structure consisting of Al/Mg/sub x/Zn/sub 1-x/O/n/sup +/-ZnO/r-sapphire, where Al and n/sup +/ type ZnO serve as the top and bottom electrode, respectively. The epitaxial Mg/sub x/Zn/sub 1-x/O films have the same epitaxial relationships with the substrate as ZnO on r-Al/sub 2/O/sub 3/, resulting in the c-axis of the Mg/sub x/Zn/sub 1-x/O being in the growth plane. This relationship promotes shear bulk wave propagation that affords sensing in liquid phase media without the dampening effects found in longitudinal wave mode BAW devices. The BAW velocity and electromechanical coupling coefficient of Mg/sub x/Zn/sub 1-x/O can be tailored by varying the Mg composition, which provides an alternative and complementary method to adjust the BAW characteristics by changing the piezoelectric film thickness. This provides flexibility to design the operating frequencies of thin film bulk acoustic wave devices. Frequency responses of devices with two acoustic wave modes propagating in the specified structure are analyzed using a transmission line model. Measured results show good agreement with simulation.     

Simulation of surface acoustic wave motor with spherical slider

The operation of a surface acoustic wave (SAW) motor using spherical-shaped sliders was demonstrated by Kurosawa et al. (1994). It was necessary to modify the previous simulation models for usual ultrasonic motors because of this slider shape and the high frequency vibration. A conventional ultrasonic motor has a flat contact surface slider and a hundredth driving frequency; so, the tangential motion caused by the elasticity of the slider and stator with regard to the spherical slider of the SAW motor requires further investigation. In this paper, a dynamic simulation model for the SAW motor is proposed. From the simulation result, the mechanism of the SAW motor was clarified (i.e., levitation and contact conditions were repeated during the operation). The transient response of the motor speed was simulated. The relationships between frictional factor and time constant and vibration velocity of the stator and the slider speed were understood. The detailed research regarding the elastic deformation caused by preload would be helpful to construct an exact simulation model for the next work.     

Spatial localization of stress-perturbing wave generated by anelectromagnetic acoustic transducer

A new apodization of electromagnetic acoustic transducer has been proposed to generate the stress perturbing wave, which has a spatially localized magnitude distribution. According to the acoustoelastic effect, a stress perturbing wave radiated into metals gives rise to an ultrasound velocity change that corresponds to the deviation of the stress in the metal. In ultrasonic measurements, it is desirable to use a narrow beam in order to obtain a high resolution. A transducer has been constructed which has a Sinc function apodization. To compare with other types of electromagnetic acoustic transducers, including a Limited Bessel-type transducer, numerical simulations are performed. It is shown that the proposed transducer provides the optimum characteristics of the spatially localized magnitude distribution. Furthermore, experimental results are presented to confirm the numerical predictions     

Quantitative imaging of Rayleigh wave velocity with a scanning acoustic microscope

An acoustic microscope operating with impulse excitation has been used to perform measurements of the Rayleigh wave velocity by measuring the time difference between the direct reflected signal and the Rayleigh wave signal. The accuracy and precision of the methodology have been examined by performing measurements at a single location on an elastically isotropic sample of E6 glass. The accuracy of the Rayleigh wave velocity measurement has been determined to be better than 0.5%. The measured Rayleigh wave velocity of (3035±5) m/s differs by 0.3% from measurements reported in the literature for a similar sample, using two different techniques. The methodology has been extended to acquire the Rayleigh wave velocity while raster scanning the sample to develop a quantitative velocity image. The background noise in the Rayleigh wave velocity image has been investigated by mapping the velocity on elastically isotropic E6 glass. Possible reasons for background noise in the images is discussed. The methodology has been extended to acquire quantitative Rayleigh wave velocity images on Ti-6Al-4V. The contrast in the images is attributed to the variation of the Rayleigh wave velocity in individual grains or regions. Applicability of the technique to investigate crystallographic texture in materials is discussed     

声表面波滤波器的离散Green函数分析法

日本学者Hashimoto提出栅格有效介电常数和离散Green函数,并结合有限元方法分析了短路金属栅阵中声表面波的传输特性。由此开发了相应的Fortran应用程序。国际上许多从事声表面波器件的研发公司都使用该程序设计他们的产品。以Rayleigh波在128°YX-LiNbO3基片、铝金属栅中传播为例,给出根据Hashimoto程序运算的结果,读取禁带下边缘和禁带上边缘所对应的相对频率的数值,代入COM理论色散关系的数学表达式中,该表达式的图形就是由COM理论色散关系而确定的波数色散曲线,以提取耦合模参数。     

带声学放大器的行波热声发动机声阻抗特性

通过分析带有声学放大器的行波热声发电系统中直线发电机的电-力-声类比图,发现直线发电机的最佳工作状态与行波热声发动机的输出声阻抗特性相关。采用DeltaEC软件计算带有声学放大器的行波热声发动机（以下简称系统）的输出声阻抗特性。计算结果发现,输出声阻抗虚部X_a为-1×10⁷ Pa·s·m^-3时,系统的最大输出声功率545.47 W,最大热声转换效率为7.2%;当输出声阻抗虚部X_a在-3.9×10⁶~-1×10⁷ Pa·s·m^-3之间变化,实部R_a在1.37×10⁶~2.31×10⁷ Pa·s·m^-3之间时,等效位移在1.89~6 mm之间变化,符合直线发电机的位移要求;结合输出声阻抗对压力与体积流率的相位差及系统工作频率的影响,发现声阻抗实部R_a应在1.37×10⁶~2.31×10⁷ Pa·s·m^-3之间,声阻抗虚部X_a在-7.5×10⁶~-1.0×107 Pa·s·m^-3之间时,系统具有较好的工作状态。     

Evaporative self-assembly assisted synthesis of polymeric nanoparticles by surface acoustic wave atomization

We demonstrate a straightforward and rapid atomization process driven by surface acoustic waves that is capable of continuously producing spherical monodispersed submicron poly-ε-caprolactone particle aggregates between 150 and 200?nm, each of which are composed of nanoparticles of 5-10?nm in diameter. The size and morphologies of these particle assemblies were determined using dynamic light scattering, atomic force microscopy and transmission electron microscopy. Through scaling theory, we show that the larger particle aggregates are formed due to capillary instabilities amplified by the acoustic forcing whereas the smaller particulates that form the aggregates arise due to a nucleate templating process as a result of rapid spatially inhomogeneous solvent evaporation. Minimization of the free energy associated with the evaporative process yields a critical cluster size for a single nucleus in the order of 10?nm, which roughly corresponds with the dimensions of the sub-50?nm particulates.     

海底沉积物声波现场测试和有限差分数值模拟研究

利用基于Biot理论的高阶交错网格有限差分算法,模拟了声源在不同位置条件下激发声波的传播,重点讨论了纵波和各种转换波的声场,并与我国某海域地区海底沉积层的现场测试数据进行了对比。研究结果表明,海底沉积层中的纵波具有明显的频散现象,这种频散现象与理论预期结果相吻合,而且由Biot理论得到的纵波频散规律和现场测试结果有较好的一致性,但对于纵波的衰减,二者符合得不好,这是因为Biot理论模型的假设条件和海底沉积层的差别较大造成的。计算声场显示,当声源放置在海水中时,在沉积层中产生三种转换波;当声源放置在沉积层中时,在沉积层中产生了多种类型的波。在某些条件下,海底沉积层中的横波速度低于慢纵波速度。     

Evaluation of film adhesion to substrates by means of surface acoustic wave dispersion

For thin film structures acoustically classified as slow-on-fast systems, modeling and evaluation of their interfacial condition are known to be very complex and difficult due to dispersion and multi-mode excitation of acoustic waves. This paper presents a quantitative model and a reliable measurement procedure established for adhesion evaluation of such film structures. An effective interface model employing a virtual intermediate layer is utilized for the dispersion prediction of the surface acoustic wave, which is affected by various interfacial conditions. Through acoustic microscopy experiments, this model presents a potential method to classify the bonding condition. Comparisons with a destructive scratch test and an acoustic imaging verify the failure mode of the film structure.     

Detection of gravity wave signals with drift of the geometric dimensions of the detector

A technique for thermal compensation of drift in the resonator length in a gravity wave detector is described. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 59–61, June, 2008.     

The characterization of sputtered polycrystalline aluminum nitrideon silicon by surface acoustic wave measurements

Polycrystalline aluminum nitride films were deposited on Si₃ N₄ coated (100) silicon substrates by the reactive sputtering method. We have carried out experiments to evaluate the effect of AlN material parameters on the SAW characteristics. The SAW transducers were fabricated by forming interdigitated Al electrodes on top of the AlN films and transmission measurements made over the frequency range from 50 MHz to 1.5 GHz. The SAW characteristics were correlated with material parameters of crystallite orientation, grain size, surface morphology and oxygen concentration. A key material parameter affecting the SAW characteristics was found to be the preferred degree of crystallite orientation with the c-axis normal to the plane of the substrate. The better oriented the AlN grains, the stronger the SAW response, the higher the SAW phase velocity, and the lower the insertion and propagation losses over the entire frequency range of measurement. Above 500 MHz the propagation losses of the well oriented films followed a frequency squared dependence only slightly higher than the reported values for the best epitaxial films. The coupling factors deduced from the transducer characteristics are in the upper range of values reported by Tsubouchi for epitaxial AlN films deposited on the basal plane of sapphire. There was a strong correlation between the X-ray diffraction intensity from the (002) planes and the oxygen content in the films     

Growth of A1N piezoelectric film on diamond for high-frequency surface acoustic wave devices

Diamond films are very desirable for application to SAW devices because of their high acoustic wave velocity, which allows the extending of the frequency limit of operation at a given interdigital transducer line-width resolution. Use of high-quality AIN as the piezoelectric layer in conjunction with diamond is also desirable because of its high SAW velocity--the highest among all piezoelectric materials--together with its excellent electrical, mechanical, and chemical properties. The problems arising in the growth of A1N films on diamond have prevented, until now, the use of this combination of materials. In this paper we present recent results on the growth of highly oriented, low-stressed A1N films on diamond. SAW propagation on A1N/diamond has been theoretically investigated together with electromechanical coupling for both the Rayleigh and the Sezawa modes. The theoretical calculations show that high SAW velocities are achievable with good coupling efficiencies. Under proper conditions very large piezoelectric couplings are predicted--k2 = 2.2 and 4% for the Rayleigh and the Sezawa wave, respectively--comparable to those observed in strongly piezoelectric single crystals such as LiNbO3, but with SAW velocities approximately two-fold higher. Experiments performed on A1N/diamond/Si SAW test devices have shown good agreement between experimental results and theoretical predictions and demonstrate the feasibility of SAW devices based on this technology.     

Simulation of acoustic wave propagation in dispersive media with relaxation losses by using FDTD method with PML absorbing boundary condition

We present a method to incorporate the relaxation dominated attenuation into the finite-difference time-domain (FDTD) simulation of acoustic wave propagation in complex media. A dispersive perfectly matched layer (DPML) boundary condition, which is suitable for boundary matching to such a dispersive media whole space, is also proposed to truncate the FDTD simulation domain. The numerical simulation of a Ricker wavelet propagating in a dispersive medium, described by second-order Debye model, shows that the Ricker wavelet is attenuated in amplitude and expanded in time in its course of propagation, as required by Kramers-Kronig relations. The numerical results also are compared to exact solution showing that the dispersive FDTD method is accurate and that the DPML boundary condition effectively dampens reflective waves. The method presented here is applicable to the simulation of ultrasonic instrumentation for medical imaging and other nondestructive testing problems with frequency dependent, attenuating media.     

Surface acoustic wave properties of proton-exchanged LiNbO3 waveguides with SiO2 film

Surface acoustic wave (SAW) properties of proton-exchanged (PE) z-cut lithium niobate (LiNbO3) waveguides with silicon dioxide (SiO2) film layers were investigated using octanoic acid. The distribution of hydrogen measured by secondary ion mass spectrometry (SIMS) showed a step-like profile, which was assumed to be equal to the waveguide depth (d). The SiO2 film was deposited on z-cut LiNbO3 waveguide by radio frequency (rf) magnetron sputtering. We investigated the important parameters for the design of SAW devices such as phase velocity (Vp), insertion loss (IL) and temperature coefficient of frequency (TCF) by a network analyzer using thin-film aluminum interdigital transducer electrodes on the upper SiO2 film surface. The experimental results showed that the Vp of SAW decreased slightly with the increase of h/lambda, where h was the thickness of SiO2 films and lambda was the wavelength. The IL of SAW increased with increased h/lambda. The TCF of SAW calculated from the frequency change of the output of SAW delay line showed an evident decrease with the increase of h/lambda. The TCF for PE z-cut LiNbO3 was measured to be about -54.72 ppm/degreees C at h/lambda = 0.08. It revealed that the SiO2 films could compensate and improve the temperature stability as compared with the TCF of SAW on PE samples without SiO2 film.     

Operation mechanism of double-mode surface acoustic wave filters with pitch-modulated IDTs and reflectors

One of the authors (KH) previously proposed pitch-modulated interdigital transducers (IDTs) and reflectors for developing low-loss and wideband longitudinally coupled double-mode SAW (DMS) filters. This paper discusses how a wide and flat passband is realized by applying the pitch-modulated IDTs and reflectors to DMS filters. It is shown that the pitch-modulated structure enables one to adjust the location of multiple resonance frequencies simultaneously by varying an effective reflective position with frequency. That is, the IDTs are pitch-modulated so that the outer portion has slightly larger pitch than the inside, and the pitch of the outermost reflectors is made largest. Accordingly, higher-order SAW resonances occur between the two pitch-modulated IDTs. The outer portion of each IDT acts as a reflector, and the inner portion is mainly responsible for SAW excitation. Lower-order SAW resonances occur between the two reflectors.