Shear Horizontal Acoustic Wave Research Articles

High-Frequency and Spectrum-Clean Shear-Horizontal Acoustic Wave Resonators with AlN Overlay.

By bonding the sub-wavelength-thick lithium niobate (LiNbO3) layer to high-phase-velocity (vp) substrates, such as Si, the shear-horizontal (SH) modes no longer couple with the bulk modes leaking into substrates. As the propagation loss is no longer the major concern for these types of nonleaky SH wave devices, the YX-LiNbO3 with a low rotation angle providing ultra-large coupling coefficient (keff2) can be used. In addition, by overlaying a high-velocity layer such as AlN on top of LiNbO3/Si, the vp of the SH wave can be significantly enhanced at a small cost of keff2. By a careful design of the stack, both the wide-band spurious (Lamb wave) and near-band spurious (Rayleigh wave) are suppressed successfully. This paper focuses on the design of layered substrate not only to optimize its resonance characteristics—series frequency (fs), quality factor (Q), keff2, and temperature coefficient of frequency (TCF)—but also for eliminating the out-of-band spurious responses. The optimized substrate design demonstrates the minimal propagation loss, high fs of 3 GHz, large keff2 of 14.4% and a spurious-free response at 0–6 GHz. These novel nonleaky SH wave devices can potentially enable the low loss and wideband processing functions, which is promising for the 5G/6G radio frequency (RF) communication systems.

A Novel Surface Acoustic Wave Biosensor for Real-Time Monitoring of Cell Contractile Properties

Introduction Contraction of cardiomyocytes is a vital property of the heart and its assessment is significant for drug discovery. At present, many researches focus on the electrophysiology detection through microelectrode arrays (MEAs) [1-2]. However, mechanical properties of cardiomyocytes is also critical for many biological processes including cell growth, motility, division, differentiation, and tissue homeostasis [3]. Currently, the atomic force microscope (AFM) has been used to measure the contractile properties of cardiomyocytes. However, the AFM is only suitable for single cells and can only measure one cell at one time. Therefore, it’s necessary to develop a detection system that can monitor the contractile properties of cardiomyocyte in a real-time and dynamic way.Recently, the surface acoustic wave (SAW) sensor has been greatly developed as a well-performed mass sensing device for label-free immunoassay due to its attractive advantages, including real-time monitoring and simplicity of use [4]. In particular, the guided shear horizontal (SH) SAW sensor, which is also known as the Love Wave sensor, has shown its advantages in biosensor applications due to its high sensitivity and stability in the liquid phase [5]. Hence, SAW is a device capable of monitoring viscoelastic properties of a population of cells, which correlates with stiffness, in a non-invasive, label free and continuous manner up to several days to weeks.In this study, a Love Wave sensor was used to study the contractile properties of HL-1 cardiomyocytes, where changes in insertion loss and phase position of the sensor can reflect the mechanical changes (contraction and viscoelasticity). Different compounds were added to test the different effects on the contractile properties of HL-1 cardiomyocytes, and the signals were analyzed by principal component analysis (PCA). Method In this study, the Love Wave sensor is constructed based on a piezoelectric quartz substrate. Interdigitated transducers (IDTs) with Ti/Au (20/200 nm) are deposited to generate pure shear horizontal acoustic waves. The input and output IDTs electrodes consist of 50 split-finger pairs with a wavelength λ=28 μm, which determines the center frequency of the sensor to be about 160 MHz [4]. The distance between IDTs centers is 200λ and the acoustic aperture is 75λ. Afterwards, the IDTs patterned substrate is guided with a 3 μm SiO2 film deposited by plasma enhanced chemical vapor deposition (PECVD). Au layer (200 nm) is deposited on top of guiding layer to improve the cell attachment on the sensor surface.A polydimethylsiloxane (PDMS) chip was designed and used as the cell culturing chamber. The height and volume of this cavity are about 10 mm and 150 μL, respectively. A portable and miniaturized multi-channel Love Wave sensor detection system was developed to detect both the insertion loss and phase signals of sensors. And then, HL-1 cardiomyocytes with 10,000 cells were seeded on the sensor chip. To test the function of the detection system, isoprenaline (ISO) and verapamil (VRP) with different concentrations were used to induce changes in the contractile properties of HL-1 cells. Results and Conclusions VRP is a calcium channel antagonist that blocks the L-type calcium channel and prevents calcium influx into the cell, thereby decreasing the cardiomyocyte contraction force. With the addition of VRP solutions, the insertion loss of Love Wave sensors increased, and the magnitudes of insertion loss increased with the increase of VRP concentration. Our results indicated that the stiffness of living HL-1 cells decreased after VRP administration. Moreover, the higher the VRP concentration is, the softer the HL-1 cells are within the dosage range tested. In contrast to VRP, ISO is positive inotropic drug. After ISO treatment, HL-1 cells wrinkled due to the traction forces. Therefore, the higher the ISO concentration, the larger the traction force and the tighter is the contact of the cells with the sensor substrate, and the stiffer the cells. Moreover, the responses of SAW sensor treated by VRP and ISO could be distinguished by PCA.As far as we know, this is the first report that study the contractile properties of a cardiomyocytes cell line based on a SAW biosensor. The affection on cardiac contractility of different compounds can be monitored by recording the changes in insertion loss and phase position of the SAW sensor. Our results demonstrated that the SAW sensor is a potential new tool for in vitro cardiac contractility evaluation and has promising applications in drug discovery, safety screening and many other fields.

Influence of plate acoustic waves on electronic transport in nanowires

The acoustoelectric effect is the generation of a acoustoelectric current in a non-biased device by a piezoactive acoustic wave. This effect has recently attracted the attention of researchers as a possible method to control the motion of massive objects in the quantum regime. We suggest using this effect for development of highly sensitive nanoelectronic sensors. The sensitivity could be increased through the use of modulation mode of operation based on the acoustic pilot signal and the transition from quasi-stationary measurement to measurement at the modulation frequency. The acoustic delay line based on shear-horizontal acoustic wave of zero order (SH0) with resonant frequency 3.25 MHz in Y-X LiNbO3 plate was produced. The nanostructure consisting of nanowire with size 20 nm × 180 nm was placed in the center between IDTs. The current–voltage characteristics of this nanowire in the presence and absence of the acoustic wave were meazured by a picoampermeter. The analysis has shown that the presence of piezoactive acoustic wave is influenced by electric current in a nanowire.

Perturbation Analysis of a Multiple Layer Guided Love Wave Sensor in a Viscoelastic Environment.

Surface acoustic wave sensors have the advantage of fast response, low-cost, and wireless interfacing capability and they have been used in the medical analysis, material characterization, and other application fields that immerse the device under a liquid environment. The theoretical analysis of the single guided layer shear horizontal acoustic wave based on the perturbation theory has seen developments that span the past 20 years. However, multiple guided layer systems under a liquid environment have not been thoroughly analyzed by existing theoretical models. A dispersion equation previously derived from a system of three rigidly coupled elastic mass layers is extended and developed in this study with multiple guided layers to analyze how the liquid layer’s properties affect the device’s sensitivity. The combination of the multiple layers to optimize the sensitivity of an acoustic wave sensor is investigated in this study. The Maxwell model of viscoelasticity is applied to represent the liquid layer. A thorough analysis of the complex velocity due to the variations of the liquid layer’s properties and thickness is derived and discussed to optimize multilayer Surface acoustic wave (SAW) sensor design. Numerical simulation of the sensitivity with a liquid layer on top of two guided layers is investigated in this study as well. The parametric investigation was conducted by varying the thicknesses for the liquid layer and the guided layers. The effect of the liquid layer viscosity on the sensitivity of the design is also presented in this study. The two guided layer device can achieve higher sensitivity than the single guided layer counterpart in a liquid environment by optimizing the second guided layer thickness. This perturbation analysis is valuable for Love wave sensor optimization to detect the liquid biological samples and analytes.

Sensor based on the slot acoustic wave for the non-contact analysis of the bacterial cells – Antibody binding in the conducting suspensions

The possibilities of using the acoustic sensor based on the slot mode in the delay line with a shear horizontal acoustic wave of zero order for the contactless analysis of the bacterial cells-antibody binding in the conducting suspensions were investigated. In this sensor, the suspension container, the bottom of which was made of the lithium niobate plate, was located above the delay line with the given width of the gap. The excitation of the slot mode in such a structure led to the appearance of the sharp resonant peaks on the frequency dependence of the insertion loss of the delay line. It has been established that the specific interaction of the bacterial cells with the antibodies in the suspensions with the different electrical conductivity leads to a change in the depth and frequency of the resonant peaks in the frequency dependence of the insertion loss of the sensor. The dependences of the changes in the depth and frequency of the resonant peaks on the conductivity of the buffer solution with the different cell concentrations were determined for the specific interaction of the “bacterial cells – antibodies”. The possibility of the use of the slot mode in the sensor to analyze the bacterial cells with the help of the antibodies in the suspensions with an initial conductivity of 5–20 μS/cm is shown. The advantage of the novel sensor is that its design allows the easy and high-quality cleaning the container from the spent cell suspension separately from the delay line.

Influence of electrical boundary conditions on profiles of acoustic field and electric potential of shear-horizontal acoustic waves in potassium niobate plates

The profiles of an acoustic field and electric potential of the forward and backward shear-horizontal (SH) acoustic waves of a higher order propagating in X-Y potassium niobate plate have been theoretically investigated. It has been shown that by changing electrical boundary conditions on a surface of piezoelectric plates, it is possible to change the distributions of an acoustic field and electric potential of the forward and backward acoustic waves. The dependencies of the distribution of a mechanical displacement and electrical potential over the plate thickness for electrically open and electrically shorted plates have been plotted. The influence of a layer with arbitrary conductivity placed on a one or on the both plate surfaces on the profiles under study, phase and group velocities of the forward and backward acoustic waves in X-Y potassium niobate has been also investigated. The obtained results can be useful for development of the method for control of a particle or electrical charge movement inside the piezoelectric plates, as well a sensor for definition of the thin film conductivity.

Wide Band Low Noise Love Wave Magnetic Field Sensor System

We present a comprehensive study of a magnetic sensor system that benefits from a new technique to substantially increase the magnetoelastic coupling of surface acoustic waves (SAW). The device uses shear horizontal acoustic surface waves that are guided by a fused silica layer with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these so-called Love waves follows the magnetoelastically-induced changes of the shear modulus according to the magnetic field present. The SAW sensor is operated in a delay line configuration at approximately 150 MHz and translates the magnetic field to a time delay and a related phase shift. The fundamentals of this sensor concept are motivated by magnetic and mechanical simulations. They are experimentally verified using customized low-noise readout electronics. With an extremely low magnetic noise level of ≈100 pT/sqrt{{rm{Hz}}}, a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. A range of additional measures to further increase the sensitivity are investigated with simulations.

The biological acoustic sensor to record the interactions of the microbial cells with the phage antibodies in conducting suspensions

The acoustic biological sensor for the analysis of the bacterial cells in conducting suspension was developed. The sensor represented the two channel delay line based on the piezoelectric plate of Y-X lithium niobate thick of 0.2mm. Two pairs of the interdigital transducers (IDT) for the excitation and reception of shear horizontal acoustic wave of zero order (SH0) in each channel were deposited by the method of photolithography. One channel of the delay line was electrically shorted by the deposition of thin aluminum film between IDTs. The second channel remained as electrically open. The liquid container with the volume of 5ml was fixed on the plate surface between IDTs by the glue, which did not cause the additional insertion loss. For the first time the influence of the conductivity of the cell suspension on the registration of the specific and nonspecific interactions of the bacterial cells with phage-antibodies (phage-Abs) was studied by means of the developed sensor. The dependencies of the change in insertion loss and phase of the output signal on the conductivity of the buffer solution at specific/nonspecific interactions for the electrically open and shorted channels of the delay line were obtained. It was shown that the sensor successfully registered the interactions of microbial cells with phage-Abs in the range of the conductivity of 2–20 μS/cm on the model samples A. brasilense Sp245 – specific phage-Abs. The sensor in the time regime of the operation fast reacted on the specific/nonspecific interaction and the time of the stabilization of the output parameters did not exceed 10min.

Investigation of interaction of shear horizontal surface acoustic wave with controlled electroinduced domain structure

In recent years, there has been great interest in developing different kinds of phononic crystals (PCs) with advanced ultrasound properties. In this study, we examined the possibility of creating a periodic domain structure controlled by an external electric field. The electric field was induced using crossed electrodes on the surface of a LiTaO3 single crystal. We investigated the domain formation process, in which the external electric field was smaller than the coercive electric field, and spontaneous polarization is not inverted. We proposed a new type of surface acoustic wave device and studied the parameters of interaction of a low-velocity shear horizontal acoustic wave with an electroinduced domain structure. This new kind of acoustic device allows the study of various ultrasound effects and the development of advanced controllable acoustoelectronic devices.

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.

Gasoline identifier based on SH0 plate acoustic waves

The present paper is devoted to the development of gasoline identifier based on zero order shear-horizontal (SH0) acoustic wave propagating in piezoelectric plate. It has been found that the permittivity of gasoline is increased when its octane number rises. The development of such identifier is experimentally demonstrated to be possible.

Shear horizontal acoustic waves propagating along two isotropic solid plates bonded with a non-dissipative adhesive layer: Effects of the rough interfaces

The aim of this paper is to provide an analytical contribution which presents the application of shear-horizontal (SH)-guided waves for the characterisation of a bi-layered structure which consists of two isotropic plates adhesively bonded using a non-dissipative thin layer of glue. The thickness of the layer of glue is assumed to be non-negligible, and the interfaces between this layer of glue and the plates are both assumed to be roughened (parallel ridges with complex shape and depth profiles). The basis of the theoretical approach is an extension of the integral formulation, in the frame of SH modal couplings due to the roughness, which has been developed previously for SH-wave propagation over a single plate with a rough surface. This approach assumes that the average roughness height is a small fraction of the thicknesses of the waveguides (the plates) everywhere. The changes, due to the roughness, in the characteristics of the fields created by a harmonic source set at the entrance edge of the structure are expressed through the mapping of the displacement and stress perturbations. Preliminary tests of the effectiveness of the model are given; they rely on the phase-matching effects of periodic profiles and pseudo-random experimental profile.

In-House Development of Shear Horizontal Acoustic Waves Based Sensitive Sensors for Bacterial Pathogens Detection

Surface acoustic wave can be generated at the free surface of an elastic solid. Interdigital transducers (IDTs) are fabricated on the piezoelectric substrate surface that will act as electrical input and output port. When appropriate AC voltage stimulus is applied to the input transducer, surface acoustic wave will be produced. The output or receiving port will detect the incident surface acoustic wave and convert it back to a suitably filtered electrical once. For this property, surface acoustic based devices were initially developed for the telecommunication purpose such as signal filters and resonators. SAW based devices have been modified to be sensors later on from for gas detections and have been moving towards biological detections recently for its ultra-sensitivity to surface perturbation. The main component of this device is the IDTs. Recently, there are several methods to produce IDTs; Ultra-Violet (UV), deep UV lithography, Electron beam (e-beam) lithography and X-ray lithography. Although, these methods can produce very fine and accurate electrodes in term of submicron size but the costs are extremely expensive. Thus, this paper will discuss the conventional CMOS method which is much more economical to produce the applicable IDTs for the bacterial pathogens sensing purpose. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based types is used in this paper as it is most suitable for the liquid based application as it has the advantage of acoustic energy is not being radiated into liquid.

Investigation of SH-Wave Fundamental Modes in Piezoelectromagnetic Plate: Electrically Closed and Magnetically Closed Boundary Conditions

It is theoretically considered the propagation (first evidence) of new dispersive shear-horizontal (SH) acoustic waves in the piezoelectromagnetic (magnetoelectroelastic) composite plates. The studied two-phase composites (BaTiO3-CoFe2O4 and PZT-5H-Terfenol-D) possess the piezoelectric phase (BaTiO3, PZT-5H) and the piezomagnetic phase (CoFe2O4, Terfenol-D). The mechanical, electrical, and magnetic boundary conditions applied to both the upper and lower free surfaces of the plate are as follows: the mechanically free, electrically closed, and magnetically closed surfaces. As a result, the fundamental modes of two new dispersive SH-waves recently discovered in book [Zakharenko, A.A. (2012) ISBN: 978-3-659-30943-4] were numerically calculated. It was found that for large values of normalized plate thickness kd (k and d are the wavenumber and plate half-thickness, respectively) the velocities of both the new dispersive SH-waves can approach the nondispersive SH-SAW velocity of the piezoelectric exchange surface Melkumyan (PEESM) wave. It was also discussed that for small values of kd, the experimental study of the new dispersive SH-waves can be preferable in comparison with the nondispersive PEESM wave. The obtained results can be constructive for creation of various technical devices based on (non)dispersive SH-waves and two-phase smart materials. The new dispersive SH-waves propagating in the plates can be also employed for nondestructive testing and evaluation. Also, it is obvious that the plates can be used in technical devices instead of the corresponding bulk samples for further miniaturization.

Fundamental modes of new dispersive SH-waves in piezoelectromagnetic plate

Fundamental modes of new dispersive shear-horizontal (SH) acoustic waves propagating in the (6 mm) piezoelectromagnetic plate are studied. These SH-waves can propagate when the following boundary conditions are exploited for both the upper and lower surfaces of the plate: (1) when the surfaces are mechanically free, electrically and magnetically closed and (2) when the surfaces are mechanically free, electrically and magnetically open. The SH-waves depend on the electromagnetic wave speed \(V_{\rm EM} =1/ {\sqrt {(\varepsilon\mu)}}\) and can only exist when the electromagnetic constant \(\alpha \ne 0\). The calculations (first evidence) were performed for the PZT-5H–Terfenol-D which is a composite with a large value of α. The limit cases of large values of α (α2 = 0.5eμ, α2 = 0.9eμ, and α2 = 0.99eμ) are studied because they satisfy the limitation condition of α2 < eμ.

Theoretical consideration of high‐sensitivity biosensor using shear horizontal acoustic waves in layered structures

AbstractRealization of high‐sensitivity biosensors is required. Acoustic wave‐based biosensors are promising because of their ability to detect immunoreactions. In this paper, a shear horizontal (SH) acoustic wave in layered structures, namely, the Love wave, is discussed on the basis of numerical calculations. To generate the Love wave, a 36YX‐LiTaO3 was chosen as a piezoelectric substrate. SiO2, polymer, and gold were chosen as guiding layer materials. First, the phase velocity and propagation loss were calculated as a function of the layer thickness. Then, an additional mass layer was loaded on the guiding layer to simulate bio‐layer deposition. Simulation results indicate that a highly sensitive biosensor was realized by using a gold guiding layer. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(4): 27–;32, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10417

Improved SHSAW transduction efficiency using grating and uniform electrode guiding

Pure shear-horizontal surface acoustic wave (SHSAW) devices have been increasingly considered for liquidphase and biosensing applications because of their ability to operate under liquid-loaded conditions and intrinsic sensitivity to mass, stiffness, viscosity, and electrical perturbations occurring at the device/fluid interface. Typically, the SHSAW is weakly guided by a free surface boundary condition (BC) or may not even exist for some materials and orientations, such as the quartz ST-90° orientation considered in this work. For a surrounding free surface BC, the interdigital transducer (IDT) typically generates strong shear-horizontal bulk acoustic waves (SHBAWs) relative to SHSAW. For that reason, guiding structures, e.g., dense and/or thick electrodes in periodic or uniform configurations, are incorporated into the design and placed between IDTs in delay-line devices to increase the ratio of transduced SHSAW power to IDT input power, ηSHSAW. The degree of ηSHSAW improvement depends on the thickness, composition, and geometry of the guiding structure. In previous work, the authors evaluated ηSHSAW using hybrid finite and boundary element method (FEM/BEM) models, but were limited to cases of stress-free or finite-thickness-grating surrounding surfaces. This work extends the analysis to the important boundary condition case of uniform finite-thickness electrode guiding, which is typically employed in liquid-phase and biosensor applications. To integrate the uniform electrode guiding structure with the SHSAW device analysis, a combined finite-length uniform electrode structure followed by an additional quarter-wavelength electrode was considered. In this work, it is shown that adjusting the quarter-wavelength electrode's film thickness and length allows cancellation of the SHSAW reflection from the edge discontinuity. As a result, the finite-length uniform guiding electrode can be treated as if it extends to infinity, and ηSHSAW can be easily obtained. In addition, the finite thickness of all electrodes is considered in the calculations. To verify the model, an IDT with uniform guiding electrodes was simulated and compared with the experimental results of a fabricated and tested device. The simulations predict SHSAW excitation directivity of 9 dB by the IDT, which is experimentally confirmed to within 0.8 dB.

Theoretical Consideration of High-Sensitive Biosensor Using Shear Horizontal Acoustic Waves in Layered Structures

Realization of high sensitive biosensors is required. As an acoustic wave based biosensor can detect immunoreactions, it is expected for applying the biosensor. In this paper, a shear horizontal (SH) acoustic wave in layered structures, namely Love wave, is discussed on the basis of numerical calculations. For generating the Love wave, a 36YX-LiTaO3 is chosen as a piezoelectric substrate. Also, SiO2, polymer, and gold are chosen as guiding layer materials. First, phase velocity and propagation loss are calculated as a function of layer thickness. Then, an additional mass layer is loaded on the guiding layer for simulating bio-layer deposition. The simulated results indicate that high sensitive biosensor is realized by using gold guiding layer.

Change in piezoelectric boundary acoustic wave characteristics with overlay and metal grating materials

This paper describes how the characteristics of shear-horizontal type piezoelectric boundary acoustic waves (PBAWs) change with combination of different overlay and metal grating materials. It is shown that PBAWs are supported in various structures provided that highly piezoelectric material(s) are employed as structural member(s). For verification, numerical simulation of different material combinations is done. The results are in good agreement with the qualitative prediction. That is, large electromechanical coupling factor K(2) is obtainable when materials having small mass densities shear modulus c(44) and shear velocity VBS; and materials having extremely large shear modulus c(44) are chosen, respectively, for overlay and metallic grating. When YX-LiNbO(3) is assumed as a substrate, for example, the best choice seems to be SiO(2) and Au for overlay and metallic grating, respectively. Although metals with extremely large rho and c(44) such as W and Ta offer large K(2), they may not be acceptable for practical PBAW applications because of their large electric resistivity.

High frequency shear horizontal plate acoustic wave devices

It has been shown recently that shear horizontal acoustic waves propagating in piezoelectric plates whose thickness h is much less than the acoustic wavelength λ possess a number of attractive properties for use in sensor and signal processing applications. In order to exploit the potential benefits of these waves, however, one needs to fabricate devices on very thin plates. We have developed a suitable fabrication method which can be used to realize devices on such thin plates. In this method, the device is first fabricated on a plate of normal thickness (approximately 500 μm) and the substrate is then lapped from the back side to reduce the thickness. The technique has been utilized to realize devices on plates of thickness less than 70 μm. A shear horizontal plate acoustic wave (SH-PAW) delay line of fundamental resonant frequency greater than 25 MHz and insertion loss less than 7 dB has been realized on a 60 μm thick Y – cut, X – propagation lithium niobate substrate. The device also shows strong response near the third harmonic frequency of 75 MHz.