Input Transducer Research Articles

Electric energy output characteristics of polyvinylidene fluoride piezoelectric transducer under pulse stress: A simplified model

Because of its excellent performance, polyvinylidene fluoride (PVDF) transducers are commonly used to convert pulse kinetic energy into electrical energy. To quantify the relationship between the transducer's input pulse stress and output electrical energy, this study established a voltage output model by simplifying the pulse stress into a triangular pulse. Then, the model's reliability was verified through three experiments, and the causes of model deviations were determined. Subsequently, the influence of the transducer (area A and piezoelectric constant K), pulse stress (pulse rise time t1 and loading rate F1), and circuit (load resistance Rm and PVDF capacitance CP) on energy conversion were analyzed with the model. Results show A, K, and F1 are directly proportional to the maximum output voltage Vmax. As Rm increases, Vmax increases and gradually approaches the limit value, AKF1t1/CP. When the peak stress remains constant, the influence of t1 on Vmax is opposite to that of Rm. When CP is larger than t1/10Rm, reducing CP leads to Vmax increases, and the increasing rate is maximized as CP approaches t1/2Rm. This study clarifies the influence of key parameters in the harvester on its energy output characteristics, which is helpful for its optimizing design in different applications.

Исследование щелевой моды в структуре, включающей линию задержки и резонирующую пьезоэлектрическую пластину

The results of the experimental and theoretical study of a structure including a delay line based on a lithium niobate plate of Y-X cut with two interdigitated transducers for exciting and receiving an acoustic wave with the shear-horizontal polarization in the frequency range 1.5-2.2 MHz are presented. The plate thickness was 0.35 mm. A resonating lithium niobate plate was located above the delay line between the transducers with a certain gap. Resonating plates of Z-X, Y-X–140° and Y-X+155° crystallographic cuts were studied. When RF voltage was applied to the input transducer, pronounced resonant absorption peaks were observed on the frequency dependence of the insertion loss. It has been established that with increasing width of the gap between the plates, the depth of the resonance peaks monotonically decreases and the peaks smoothly disappears. Moreover, for most peaks, the quality factor decreases with increasing gap width. The theoretical analysis of such structures showed good agreement between the theoretical and the experimental results. The developed structure shows promise for its use for multiparameter analysis of various liquids

Mechanism study of aging oil demulsification and dehydration under ultrasonic irradiation

With the tertiary oil recovery in the oilfield, the content of aging oil emulsion with high water content and complex components has become more prevalent, so it is crucial for aging oil to break the emulsification. In this paper, the experimental laws of water content are explored under the conditions of different transducer input powers through the ultrasonic reforming of aging oil, and the microscopic topography, particle size, components, etc. of oil samples before and after the irradiation of ultrasound are characterized through the microscopic analysis, particle size analysis and component analysis and other ways. The results show that the oil samples achieve the effect of demulsification and dehydration in the presence of ultrasonic cavitation effect, with a maximum dehydration rate of 98.24 %, and that the dehydration rate follows an “M−type” trend with the increase of power. The results of microscopic and particle size analyses demonstrate that ultrasonic irradiation destabilizes the oil–water interfacial membrane, and causes droplets of different sizes to collide, agglomerate, and settle. It was also observed that the droplets of the emulsion system are more evenly distributed and the intervals are increased. Furthermore, we hypothesize that ultrasound may be less irreversible in demulsification and dehydration of aging oil.

Piezoelectric Microacoustic Metamaterial Filters.

We present the first microacoustic metamaterial filters (MMFs). The bandpass of the reported MMFs is not generated by coupling, electrically or mechanically, various acoustic resonances; instead, it originates from the passbands and stopbands of a chain of three acoustic metamaterial (AM) structures. These structures form an AM transmission line (AMTL) and two AM reflectors (AMRs), respectively. Two single metal strips serve as input and output transducers with a wideband frequency response. Since MMFs do not rely on resonators, they do not require high-resolution trimming or mass-loading steps to accurately tune the resonance frequency difference between various microacoustic resonant devices. These steps often involve finely controlling the thickness of a device layer, with resolutions that can be as low as a few Angstroms when building GHz filters. The acoustic bandwidth of MMFs is mostly determined by geometrical and mechanical parameters of their AM structures. MMFs necessitate external circuit components for impedance matching, in contrast to the existing microacoustic filters that often employ circuit components only to eliminate ripples within their passband. We have designed and constructed the first MMFs from a 400-nm-thick scandium-doped aluminum nitride (AlScN) film using a 30% scandium-doping concentration. These devices operate in the radio frequency (RF) range. We validated these devices' performance through finite-element modeling (FEM) simulations and through measurements of a set of fabricated devices. When matched with ideal circuit components, the built MMFs exhibit filter responses with a center frequency in the ultrahigh-frequency range, a fractional bandwidth (FBW) of ~2.54%, a loss of ~4.9 dB, an in-band group delay between 70 ± 25 ns, and a temperature coefficient of frequency (TCF) of ~22.2 ppm/° C.

A holistic physics-informed neural network solution for precise destruction of breast tumors using focused ultrasound on a realistic breast model

<p>This study presented a novel approach for the precise ablation of breast tumors using focused ultrasound (FUS), leveraging a physics-informed neural network (PINN) integrated with a realistic breast model. FUS has shown significant promise in treating breast tumors by effectively targeting and ablating cancerous tissue. This technique employs concentrated ultrasonic waves to generate intense heat, effectively destroying cancerous tissue. In previous finite element method (FEM) models, the computational demands of handling extensive datasets, multiple dimensions, and discretization posed significant challenges. Our PINN-based solution operated efficiently in a mesh-free domain, achieving remarkable accuracy with significantly reduced computational demands, compared to conventional FEM techniques. Additionally, employing PINN for estimating partial differential equations (PDE) solutions can notably decrease the enormous number of discretized elements needed. The model employed a bowl-shaped acoustic transducer to focus ultrasound waves accurately on the tumor location. The simulation results offered detailed insights into each step of the FUS treatment process, including the generation of acoustic waves, the targeting of the tumor, and the subsequent heating and ablation of cancerous tissue. By applying a 3.8 nm displacement amplitude of transducer input pulse at a frequency of 1.1 MHz for 1 second, the temperature at the focal point elevated to 38.4 ℃, followed by another 90 seconds of cooling time, which resulted in significant necrosis of the tumor tissues. Validation of the PINN model's accuracy was conducted through FEM analysis, aligning closely with real-world FUS therapy scenarios. This innovative model provided physicians with a predictive tool to estimate the necrosis of tumor tissue, facilitating the customization of FUS treatment strategies for individual breast cancer patients.</p>

Focusing Reflected Ultrasound Using Boundary Element Model for Mid-Air Tactile Presentation.

Ultrasound focusing with curved reflectors has various advantages in mid-air tactile presentation. First, tactile sensations can be presented from various directions without placing a large number of transducers. It also avoids conflicts in the arrangement of transducer arrays with optical sensors and visual displays. Furthermore, the blurring of the focus can be suppressed. We propose a method for focusing reflected ultrasound by solving the boundary integral equation for the sound field on a reflector divided into elements. This method does not require a prior measurement of the response to each transducer at the tactile presentation point, as in the previous method. It enables real-time focusing on arbitrary locations by formulating the relationship between the transducer input and the reflected sound field. This method also enhances the focus intensity by incorporating the tactile presentation's target object into the boundary element model. Numerical simulations and measurements showed that the proposed method could focus ultrasound reflected from a hemispherical dome. A numerical analysis was also performed to determine the region where focus generation with sufficient intensity was possible.

Review of Surface Acoustic Wave Sensors for the Detectionand Identification of Toxic Environmental Gases/Vapours

Detection and identification of toxic environmental gases have assumed paramount importance precisely in the defense, industrial and civilian security sector. Numerous methods have been developed for the sensing of toxic gases in the environment ever since surface acoustic wave (SAW) technology came into existence. Such SAW sensors called electronic nose (E-Nose) sensor use the frequency response of a delay line/resonator. SAW device is focused and given importance. The selective coating between input and output interdigital transducers (IDTs) in the SAW device is responsible for corresponding changes in operating frequency of the device for a specific gas/vapour absorbed from the environment. A suitable combination of well-designed SAW delay lines with selective coatings not only help to improve sensor sensitivity and selectivity but also leads to the minimization of false frequency alarms in the E-Nose sensor. This article presents a comprehensive review of design, development, simulation and modelling of a SAW sensor for potential sensing of toxic environmental gases.

Multi-plane Diffractive Acoustic Networks.

Acoustic holograms are able to control pressure fields with high spatial resolution, enabling complex fields to be projected with minimal hardware. This capability has made holograms attractive tools for applications including manipulation, fabrication, cellular assembly, and ultrasound therapy. However, the performance benefits of acoustic holograms have traditionally come at the cost of temporal control. Once a hologram is fabricated, the field it produces is static and cannot be reconfigured. Here, we introduce a technique to project time-dynamic pressure fields by combining an input transducer array with a multi-plane hologram, which is represented computationally as a diffractive acoustic network (DAN). By exciting different input elements in the array, we can project distinct and spatially-complex amplitude fields to an output plane. We numerically show that the multi-plane DAN outperforms a single-plane hologram, while using fewer total pixels. More generally, we show that adding more planes can increase the output quality of the DAN for a fixed number of degrees of freedom (pixels). Finally, we leverage the pixel efficiency of the DAN to introduce a combinatorial projector that can project more output fields than there are transducer inputs. We experimentally demonstrate that a multi-plane DAN could be used to realize such a projector.

Nanostructured Silicon-Based Surface Acoustic Wave Sensor for CO2 Gas Detection

Surface acoustic wave (SAW) gas sensors with nanostructured material-based sensing layers are desirable in gas sensing owing to their high sensitivity, and their fast response and recovery time. In this work, a novel SAW gas sensor with a nanostructured silicon (Si)-based sensing layer with four pairs of aluminum-based input and output interdigital transducer (IDT) is developed and fabricated. A finite-element analysis (FEA) is used to determine the sensitivity while varying the height of the nanostructured Si. As a proof of concept, the SAW sensor is tested for carbon dioxide (CO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}$ </tex-math></inline-formula> ) gas concentrations, ranging from 500 to 2000 ppm. The results demonstrate that the developed SAW sensor with a nanostructured Si-based sensing layer showed a maximum frequency shift of 4.62177 kHz with a response and a recovery time of 31 and 40.5 s, respectively, for a 2000-ppm CO2 gas concentration. The developed nanostructured Si as a sensing layer for the SAW gas sensor demonstrated higher sensitivity than previously reported devices and has promising potential to be used as a sensing layer for next-generation MEMS SAW gas sensors.

High-Performance SAW Device Based on Zinc-Oxide Substrate With Electric Field Regulating Graphene Film Conductivity for Signal Amplifier

In this study, a high-performance surface acoustic wave (SAW) device based on a multi-layer graphene amplifier is proposed, which is mainly composed of a zinc-oxide (ZnO) substrate, an interdigital transducer (IDT) input, a graphene sensing layer, metal electrodes and a fork finger transducer output. The sensor uses graphene’s unique band structure and the electron transport properties of the high mobility of the carrier with extremely small temperature influence to amplify the signal of the SAW caused by the sensing signal, thereby improving the sensitivity of the SAW sensor. The influence of graphene variable conductivity controlled by the uniform electric field on SAW amplifier devices in the near field is studied and analyzed. A small size surface acoustic wave device is fabricated with microelectromechanical system (MEMS) technology. The results show that the resonant frequency of the sensor is about 72 MHz, and the maximum amplification performance is 36 dB/cm. It is found that the SAW amplifier proposed in ZnO piezoelectric crystals exhibits superior performance in graphene-based SAW amplifiers.

Multimode Design and Piezoelectric Substrate Anisotropy Use to Improve Performance of Acoustic Liquid Sensors.

Using acoustic wave modes propagation in piezoelectric plates loaded with conductive liquids, peculiarities of the mode-liquid acoustoelectric interaction are studied. It is found that (i) in contrast to bulk and surface acoustic waves propagating in piezoelectric semiconductors, the acoustoelectric attenuation of the modes is not symmetric in respect to its maximum, (ii) a large increase in attenuation may be accompanied by a small decrease in phase velocity and vice versa, (iii) the peculiarities are valid for “pure” (without beam steering) and “not pure” (with beam steering) modes, as well as for modes of different orders and polarizations, and (iv) conductivity of test liquid increases electromagnetic leakage between input and output transducers, affecting results of the measurements. To decrease the leakage, the liquid should be localized between transducers, outside the zone over them. If so, the mode sensitivity may be as large as 8.6 dB/(S/m) for amplitude and 107°/(S/m) for phase. However, because of comparable cross-sensitivity towards viscosity and dielectric permittivity, modes with selective detection of liquid conductivity are not found.

Possibilities of Reliable Ultrasonic Detection of Subwavelength Pipework Cracks

An occurrence of cracks in pipework could lead to potentially very dangerous malfunction in some critical engineering systems such as power plants. There is a clear trend of replacing traditional manual testing with non-invasive in-situ methods that should detect crack formation in its early stage. Such as approach would enable replacing of unhealthy pipe components during the regular periodic outages. Ultrasonic testing is known to be a rather mature and reliable technology. However, it suffers from serious problems in detection of the cracks of subwavelength size. This paper attempts to soften aforementioned problems by investigating the influence of a duration of the unipolar excitation signal on the achieved resolution. In addition, the transducer input electricalimpedance of NDT transmitter was measured by using different excitation pulses and their levels and the results are compared with those obtained using traditional frequency sweeping method at low excitation levels. Finally, use of some advanced signal processing algorithms that might lead to the automatic detection of subwavelength voids, in scenarios with low signal-to-noise ratio, is discussed.

Development and validation of low-intensity pulsed ultrasound systems for highly controlled in vitro cell stimulation

This work aims to describe the development and validation of two low-intensity pulsed ultrasound stimulation systems able to control the dose delivered to the biological target. Transducer characterization was performed in terms of pressure field shape and intensity, for a high-frequency range (500 kHz to 5 MHz) and for a low-frequency value (38 kHz). This allowed defining the distance, on the beam axis, at which biological samples should be placed during stimulation and to exactly know the intensity at the target. Carefully designed retaining systems were developed, for hosting biological samples. Sealing tests proved their impermeability to external contaminants. The assembly/de-assembly time of the systems resulted ~3 min. Time-domain acoustic simulations allowed to precisely estimate the ultrasound beam within the biological sample chamber, thus enabling the possibility to precisely control the pressure to be transmitted to the biological target, by modulating the transducer's input voltage. Biological in vitro tests were also carried out, demonstrating the sterility of the system and the absence of toxic and inflammatory effects on growing cells after multiple immersions in water, over seven days.

Evaluating the impact of acoustic impedance matching on the airborne noise rejection and sensitivity of an electrostatic transducer

To capture sound from solid mediums, such as the human body or musical instruments, transducers designed for airborne sound pickup are typically used. Acoustic impedance mismatches between the medium and transducer decrease the energy captured and increase noise corruption. Here, we demonstrate the improved sensitivity and airborne noise rejection of an electrostatic transducer with an acoustic impedance matched to the medium of interest. The transducer produces an electrical response when mechanical vibrations compress the distance between an elastomer with patterned microstructures and a charged electret film. Using a statistical model generated through an I-optimal design of experiments, the elastomer is fabricated with a specific polymer and concentration of nanoparticles to possess a targeted acoustic impedance. Transducers containing elastomers with impedances in the range of 1 to 2.2 MRayls are assembled and characterized on simulators emulating the human body and a wooden instrument. The noise rejection is quantified using the coherence between the captured transducer signal and the simulated ambient noise. Sensitivities are similarly characterized by comparing the transducer signal and input simulator signal. With an impedance closely matched to the medium of interest, the transducer demonstrates a 2V/N sensitivity and 35 dB SNR improvement compared to an airborne transducer.

Printed Acoustic Sensor for Low Concentration Volatile Organic Compound Monitoring

Printed electronics employing flexible substrate offers prospective features for various applications such as, tactile sensing, energy harvesting, wearable electronics and acoustic wave sensors. In this work, an acoustic FPW (flexural plate wave) sensor is printed on thin and flexible PZT-PDMS (lead zirconate titanate-poly dimethyl siloxane) composite film with silver ink. The prototype FPW resonator has a resonant frequency of 22.65 MHz with an attenuation of -1.552 dBm. Gravimetric mass sensitivity of the sensor was measured by applying PDMS layers in between the input and output interdigital transducers (IDTs). The mass sensitivity was measured to be -7.8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /g. The sensor is highly responsive to VOCs (volatile organic compounds) with PDMS as a sensing layer. Gas sensitivities with acetic acid and toluene concentrations were measured to be 0.66 and 160.63 kHz/ppm, respectively. The limit of detection for acetic acid and toluene were 10.9 and 0.03 ppm, respectively. Further, the sensor shows good repeatability and response time with both the VOCs. The thermal stability and high piezoelectric charge coefficient of PZT-PDMS composite compared to other piezoelectric composite and polymer substrates are advantageous for the flexible printed sensor. The reported FPW gas sensor shows potential for low concentration measurement of VOCs.

Experimental Evaluation and Kinetic Analysis of Direct-Contact Ultrasonic Fabric Drying Process

Abstract Over the past two decades, due to the rising energy prices and growing awareness about climate change, significant efforts have been devoted to reducing the energy consumption of various home appliances. However, the energy efficiency of clothes dryers has little improvement. Recent innovations in the direct-contact ultrasonic fabric drying technique offer new opportunities for energy saving. In this technique, high-frequency mechanical vibrations generated by the ultrasonic transducer are utilized to atomize water from a fabric in the liquid form, which demonstrates great potential for reducing energy use and drying time of the fabric drying process. Here, for the first time, fabric drying kinetics under different direct-contact ultrasonic drying conditions were investigated experimentally and analytically. The drying processes of four kinds of fabrics were experimentally tested under different ultrasonic transducer vibration frequency (115, 135, and 155 kHz) and input power (1.2, 2.5, and 4.4 W) conditions. According to the experimental data, five different kinds of models were applied to quantify the drying kinetics of fabrics during direct-contact ultrasonic drying. The models not only incorporated the transducer parameters but also the parameters related to the nature of fabric. Our evaluation results of model prediction performance demonstrated that the two empirical models, i.e., the Weibull model and the Gaussian model, were superior to the three semi-theoretical models for anticipating the drying kinetics of fabrics under direct-contact ultrasonic drying. Furthermore, the Weibull model is more suitable for practical energy-efficient direct-contact ultrasonic fabric drying applications compared with the Gaussian model.

Research of Pulse Signals Mutual Influence in Polysphygmography of Radiary Arteries

The independence estimation results of synchronously recorded pulse signals in distal parts of human radial arteries are presented in this paper. The study is carried out by the methods of structural-functional and simulation modeling in approximation of an equivalent planar movement of the biological object structural elements. Their elastic characteristics are taken into account using by electromechanical analogies. The correctness of the proposed mathematical model of pulse signals at transducer input is confirmed experimentally. The experimental studies are carried out using a device that represents piezoelectric and piezoresistive transducers connected in series (mechanically). The stiffness and the operating frequency range of the device are equal to 5217 ± 430 N/m and 0.04–32 Hz, respectively. Measurement results for a pulse signal of the piezoelectric transducer (pelot diameters are equal to 6 and 8 mm) and the piezoresistive force sensor show that in the range of transducer to zone surface pressing up to 2 N, the length of arteries areas, forming pulse signals, does not exceed 13 mm and is situated within zones accepted in oriental medicine.

Focused Ultrasound Assistance to the MOS Gas Sensor System.

It is known that the ultrasound-assisted metal oxide semiconductor (MOS) gas sensor system can improve the sensitivity and lower detection limit (LDL) of a MOS gas sensor. The existing ultrasound-assisted MOS gas sensor system employs the standing-wave ultrasonic field. As the size of the sensing element is much smaller than that of the ultrasonic field, energy utilization rate of the ultrasonic subsystem has been very poor. In this work, we propose a method to raise the energy utilization rate, and the limit-sensing properties of the ultrasound-assisted MOS gas sensor system, which utilizes the focused ultrasound generated by a low-frequency ultrasonic transducer with a concave radiation face. By placing the sensing element at the focal region, the electric power input of the ultrasonic transducer can be decreased by about 50% for the same sensing response. Moreover, the maximum sensitivity can be increased by 45%, and the LDL can be decreased by 50% by the new method.

Quantifying macro- and microscale alignment of carbon microfibers in polymer-matrix composite materials fabricated using ultrasound directed self-assembly and 3D-printing

Aligning microfibers along a user-specified direction is important to fabricate polymer-matrix composite materials with tailored properties, including anisotropic electrical and thermal conductivity and high strength-to-weight ratio. Building on our earlier work, we employ ultrasound directed self-assembly to align carbon microfibers along user-specified directions in photopolymer resin and use stereolithography to cure the resin and 3D print composite materials. We quantify macro- and microscale alignment of microfibers in the matrix as a function of weight fraction and dimensionless ultrasound transducer separation distance and input power. Multiple regression analysis expresses microfiber alignment as a function of the fabrication process parameters and shows that microscale alignment is primarily determined by microfiber weight fraction, whereas macroscale alignment is a function of microfiber weight fraction, dimensionless ultrasound transducer separation distance and input power. Relating microfiber alignment to the fabrication process parameters is a crucial step towards 3D-printing polymer-matrix composite materials with tailored material properties.

Application of Markov process/mathematical modelling in analysing communication system reliability

PurposeThe purpose of this paper is to analyse the main components of a wireless communication system, e.g. input transducer, transmitter, communication channel and receiver on the basis of their interconnection for evaluating the various reliability measures for the same.Design/methodology/approachMarkov process and mathematical modelling is used to formulate a mathematical model of the considered system (on the basis of various failures/repairs).FindingsReliability of the wireless communication system with respect to its components failure is obtained and explained with the graphs. Also, critical components of the system are identified with the aid of sensitivity analysis. At last, mean time to failure with variation in various failures is obtained.Originality/valueIn the present paper, a mathematical model based on the working of the wireless communication system has been developed. Conclusions in this paper are good references for the improvement in the same.