Transducer Design Research Articles

Theoretical modeling, verification, and application study on a novel bending-bending coupled piezoelectric ultrasonic transducer

Commercialized ultrasonic algae removal systems generally adopt multiple Langevin ultrasonic transducers to produce omnidirectional ultrasound radiation, leading to complex configuration and control systems, low efficiency, high energy consumption, and high cost. In order to ease these issues, a novel bending-bending coupled piezoelectric ultrasonic transducer is proposed, theoretically modeled, and experimentally investigated in this study. Two groups of piezoelectric ceramics with dual polarization zones are sandwiched between two metal blocks, which are used to produce two orthogonal and identical bending vibration modes. With the coupling of the two bending vibration modes, the proposed sandwich piezoelectric transducer can produce omnidirectional ultrasonic irradiation for algae removal, which can greatly simplify the configuration and control system of ultrasonic algae removal system, lower energy consumption, and improve removal efficiency. A novel transfer matrix model of describing the bending-bending coupled vibration is first created for the combined piezoelectric element with dual polarization zones by simultaneously considering its electrical and mechanical properties. Then an electromechanical coupling model of the proposed transducer is developed to reveal its dynamic behavior. In addition, the vibration characteristics of the transducer prototype are tested, in order to verify the feasibility of the transducer design and operating principle and to confirm the correctness of the developed electromechanical coupling model. Finally, an application study is carried out to evaluate the algae removal effect of the proposed transducer prototype. At ultrasonic intensities of 0.014 W/mL and 0.021 W/mL, the algal removal rate, respectively, reached 45.83% and 63.27% when the ultrasonic irradiation time was 60 min, presenting efficient algae removal effect. Compared to the traditional Langevin ultrasonic transducers, the proposed transducer can achieve omni-directional ultrasonic radiation, greatly simplifying the structure and drive circuit of the ultrasonic algae removing system. It has a good application prospect in the field of environmental protection and water purification.

Design of Planar Array Transducers Based on Connected 1–3 Piezoelectric Composites

To improve the transmission performance and preparation of a transducer array, two planar array transducers based on connected 1–3 piezoelectric composites as a matrix were designed. Each transducer contained 25 array elements with a gap of 1 mm between them. The length, width and height of each array element were 1 mm, 26 mm and 5 mm, respectively. Two kinds of array transducers were tested through finite element simulation and experiments. The array transducer prototype was fabricated based on two kinds of composite materials, and the fabrication cycle was short. Our results show that the maximum transmission voltage response of the two-phase 1–3 full array driver is up to 179 dB at 200–400 kHz and the acoustic radiation intensity can be increased by up to 22% compared with the traditional splicing transducer array. It is suitable for short-range target positioning and measurement. Moreover, in the single element mode, the beam of the three-phase 1–3 transducer has no sidelobe and a single element −3 dB beam width of up to 91°. Furthermore, the beam width of the two-phase 1–3 type is 54°, and the acoustic radiation breadth is improved by 40.6%. The three-phase 1–3 type array transducer has the characteristics of concentrated acoustic transmission energy of the whole array, and its −3 dB beam width is 3.5°. The beam width decreased by 12.5%, indicating that the three-phase 1–3 type transducer is suitable for short-range target detection and perception. The two array transducers have their own advantages in transmitting the voltage response and beam width, which must be selected on the basis of the requirements of practical applications.

Characterization of Giant Magnetostrictive Materials Using Three Complex Material Parameters by Particle Swarm Optimization

Complex material parameters that can represent the losses of giant magnetostrictive materials (GMMs) are the key parameters for high-power transducer design and performance analysis. Since the GMMs work under pre-stress conditions and their performance is highly sensitive to pre-stress, the complex parameters of a GMM are preferably characterized in a specific pre-stress condition. In this study, an optimized characterization method for GMMs is proposed using three complex material parameters. Firstly, a lumped parameter model is improved for a longitudinal transducer by incorporating three material losses. Then, the structural damping and contact damping are experimentally measured and applied to confine the parametric variance ranges. Using the improved lumped parameter model, the real parts of the three key material parameters are characterized by fitting the experimental impedance data while the imaginary parts are separately extracted by the phase data. The global sensitivity analysis that accounts for the interaction effects of the multiple parameter variances shows that the proposed method outperforms the classical method as the sensitivities of all the six key parameters to both impedance and phase fitness functions are all high, which implies that the extracted material complex parameters are credible. In addition, the stability and credibility of the proposed parameter characterization is further corroborated by the results of ten random characterizations.

Effect of Geometrical Parameters On Sensitivity And Volume Of Dual Octal Ring

Force transducer is one of the load cell which is used to measure force or weight, pressure etc. various types of transducers are manufacturing for various applications. But most of strain gauge type of transducer is used. In current research, optimization of octagonal type of force transducer design is carried out by maximizing sensitivity and minimizing the volume. Force transducer is analyze with the help of finite element method and find the critical parameters, its effect also as sensitivity and volume. Response surface methodology is used for experimental set up. For performance of all parameters analysis of variance is carried out and multi-objective optimization is also performed.

Embedded dual PZT-based monitoring for curing of concrete

Monitoring the hardening of concrete during construction, is important to ensure proper strength gain and timely removal of formwork without compromising safety. Existing non-destructive testing (NDT) techniques mostly require sophisticated equipment and technical expertise, which makes it less applicable for field monitoring. Alternatively, lead zirconate titanate (PZT)-based electromechanical impedance (EMI) technique is under research, as an option for monitoring the hydration of concrete. The current study proposes a transducer design using an innovative configuration of PZT patches on metal plate, which enables segregation of flexural and axial modes while measuring EMI. The resultant peaks are more prominent, making its variation easier to track. The effectiveness of this configuration is studied by embedding the smart piezoelectric-based plate in the concrete during casting and recording the electromechanical admittance throughout the curing period. The frequency shift of the first flexural/axial peak, is a good indicator of the strength gain during this period. This has been verified for ordinary Portland cement (OPC) and fly ash-based geopolymer (GP). The results show that the frequency shift curve follows the isothermal calorimetry curves beyond the main hydration peak.

Electronic targeting of brain stimulation: design and validation of a 5-coil multi-locus TMS transducer

Electronic targeting of brain stimulation: design and validation of a 5-coil multi-locus TMS transducer

A Type of EMAT for Simultaneous Detection of Two Components of Rayleigh Wave

A new design of electromagnetic acoustic transducer (EMAT) is proposed for simultaneous measurement of in-plane and out of plane displacement components of Rayleigh wave. The EMAT consists of nine magnets and two meander-line-coils (MLCs). There almost only exists vertical or horizontal magnetic field at some specific positions in the magnetic field generated by the EMAT. By adjusting the interval between adjacent conductors and the position of conductors, the conductors in one coil are almost only in the vertical magnetic field and the conductors in the other coil are almost only in the horizontal magnetic field. Therefore, the two coils in this EMAT will almost only react with in-plane and out of plane displacements respectively. With this EMAT, repeated positioning or large area is not required during the measurement process. In addition, this EMAT can measure the two displacement components simultaneously without calculation. Meanwhile, this EMAT is much more sensitive to the ultrasonic waves for the magnetic field generated by the EMAT is enhanced. The measurement results of this EMAT are consistent with those of conventional EMATs, which indicates that the measurement results are accurate and reliable.

Design and Fabrication of a Stacked Three-Phase Piezoelectric Composites Ring Array Underwater Ultrasound Transducer.

A stacked three-phase piezoelectric composites ring array underwater ultrasound transducer was developed in this paper. The circular structure of three-phase piezoelectric composite with a large open angle was improved based on the 1-3 piezoelectric composites. The structure size of the transducer’s sensitive component was designed by using ANSYS simulation software, and the single-ring samples of three-phase piezoelectric composites with different thicknesses were fabricated. Based on the bandwidth broadening theory of multimode coupled vibration, the piezoelectric composite ring-shaped sensitive component was fabricated by the piezoelectric composite curved-surface-forming process. According to the design structure of the transducer, the stacked three-phase piezoelectric composites ring array underwater ultrasound transducer was processed. The experimental results show that the maximum transmission voltage response is 154 dB, the open angle of the horizontal beam reaches 360°, and the bandwidth of −3 dB is 86 kHz. The developed transducers achieved a high frequency, broadband, and large open angle to radiate sound waves.

Electrochemical Tilt Sensors With Symmetric Concentric Electrode Pairs

This paper presented the principle, design, fabrication, and characterization of Molecular Electronic Transducer (MET) single-axis tilt sensors. The proposed sensor has a circular channel deposited with symmetric concentric electrode pairs and half-filled with a liquid electrolyte. Such inclination-dependent liquid level is detected by the differential current from the electrochemical reaction at the two symmetric concentric electrode pairs. In order to reduce the form factor, an organic solvent is added to the aqueous electrolyte to lower the surface tension force. Limited by the liquid motion and reaction rate, the sensors are capable to measure tilt angle under static conditions only. From the tilt angle stepping experiments, the performance of the proposed tilt sensors is characterized and compared. The sensors’ response time is dominated by the electrochemical equilibrium arrival time. They can achieve a low discrimination threshold of 0.016° and a short time constant of 0584s within the ±85° measurement range with a power consumption of less than 0.1mW. Compared to previously reported MET tilt sensors with a parallel swirl electrode configuration, the signal-to-noise ratio and response time are improved significantly.

Input-output analysis of fluid–structure interaction to optimize stone breakage in burst-wave lithotripsy

Burst-wave lithotripsy is a non-invasive treatment of kidney stones using short pulses of focused ultrasound. In this talk, we present the use of input-output analysis to optimize the design and control of a multi-element array transducer to achieve optimal stone breakage. The analysis is based on a linear fluid-structure coupled system that maps the acoustic forcing from individual elements to the stress in a stone of assumed shape, size, and composition. We determine the optimal frequency and optimal distribution of the phase and amplitude across the aperture by maximizing a cost function that represents the strain energy in stone. The optimal parameters are obtained by applying a state-of-the-art, randomized singular value decomposition (SVD) to the discrete linear operator. The results show that carefully controlling the relative phase and amplitude between elements can increase the strain energy (by 2-3 times in certain cases) compared to a uniform distribution under the same input energy. This suggests that the stone fragmentation can be accelerated or performed with lower energy for safer treatment. The improvement is interpreted and validated by combining high-fidelity simulations with high-speed camera images of crack formation in model stones from in vitro- experiments. [Work supported by NIH, Grant No. P01-DK043881.]

Introduction to the Technical Committee on Engineering Acoustics

This talk will introduce ongoing work in the Technical Committee on Engineering Acoustics (TCEA) of the Acoustical Society of America, which is one of the most diverse Technical Committees of the Society. Engineering Acoustics encompasses the theory and practice of creating tools to generate and investigate acoustical phenomena and then to apply the knowledge of acoustics to practical utility. This includes the design and modeling of acoustical and vibrational transducers, arrays, and transduction systems in all media and frequency ranges. It is also concerned with the design of acoustical instrumentation, metrology, and the calibration of those systems. It further considers all aspects of measurement, fabrication, and computational techniques as they relate to acoustical phenomena and their utility. The talk will provide an introduction of a broad range of research topics in TCEA, with specific highlights on exciting new areas of research.

Efficient electromagnetic transducers for spin-wave devices

This paper presents a system-level efficiency analysis, a rapid design methodology, and a numerical demonstration of efficient sub-micron, spin-wave transducers in a microwave system. Applications such as Boolean spintronics, analog spin-wave-computing, and magnetic microwave circuits are expected to benefit from this analysis and design approach. These applications have the potential to provide a low-power, magnetic paradigm alternative to modern electronic systems, but they have been stymied by a limited understanding of the microwave, system-level design for spin-wave circuits. This paper proposes an end-to-end microwave/spin-wave system model that permits the use of classical microwave network analysis and matching theory towards analyzing and designing efficient transduction systems. This paper further compares magnetostatic-wave transducer theory to electromagnetic simulations and finds close agreement, indicating that the theory, despite simplifying assumptions, is useful for rapid yet accurate transducer design. It further suggests that the theory, when modified to include the exchange interaction, will also be useful to rapidly and accurately design transducers launching magnons at exchange wavelengths. Comparisons are made between microstrip and co-planar waveguide lines, which are expedient, narrowband, and low-efficiency transducers, and grating and meander lines that are capable of high-efficiency and wideband performance. The paper concludes that efficient microwave-to-spin-wave transducers are possible and presents a meander transducer design on YIG capable of launching varvec{lambda = 500},nm spin waves with an efficiency of − 4.45 dB and a 3 dB-bandwidth of 134 MHz.

Weighted differential evolution heuristics for improved multilayer piezoelectric transducer design

Piezoelectric transducers are designed for wide applications of underwater sonar, energy harvesting, biomedical and nondestructive testing in terms of higher sensitivity and broad bandwidth. Multilayer transducers have well-known advantages of higher sensitivity and thus can be optimized by varying layer thicknesses of active material. The present study deals with mathematical optimization of multilayer transducers exploiting weighted differential evolution (WDE) based computational heuristics for optimized piezoelectric transducer design while satisfying the constraint of constant total thickness. Fitness evaluation is carried out on the basis of one dimensional model (ODM) for simple multilayer, multilayer with bondlines and transducer with bondlines and matching for piezoelectric materials including PZT5h, PMN-PT and piezocomposite with PMN-PT for different loading media. WDE exploited along with ODM for the transducer models has demonstrated the efficacy, reliability and applicability of the proposed scheme. Comparative study of the proposed WDE-ODM with its counterparts including simulated annealing, genetic algorithms, and particle swarm optimization, reveal better performance in terms of accuracy, complexity and convergence metrics for different number of layers for simple transducers. Applicability of WDE-ODM on piezoelectric structures with bondlines, and matching layers has also been accessed and validated.

Sensitivity Analysis of a Portable Wireless PCB-MEMS Permittivity Sensor Node for Non-Invasive Liquid Recognition.

Dielectric characteristics are useful to determine crucial properties of liquids and to differentiate between liquid samples with similar physical characteristics. Liquid recognition has found applications in a broad variety of fields, including healthcare, food science, and quality inspection, among others. This work demonstrates the fabrication, instrumentation, and functionality of a portable wireless sensor node for the permittivity measurement of liquids that require characterization and differentiation. The node incorporates an interdigitated microelectrode array as a transducer and a microcontroller unit with radio communication electronics for data processing and transmission, which enable a wide variety of stand-alone applications. A laser-ablation-based microfabrication technique is applied to fabricate the microelectromechanical systems (MEMS) transducer on a printed circuit board (PCB) substrate. The surface of the transducer is covered with a thin layer of SU-8 polymer by spin coating, which prevents it from direct contact with the Cu electrodes and the liquid sample. This helps to enhance durability, avoid electrode corrosion and contamination of the liquid sample, and to prevent undesirable electrochemical reactions to arise. The transducer’s impedance was modeled as a Randles cell, having resistive and reactive components determined analytically using a square wave as stimuli, and a resistor as a current-to-voltage converter. To characterize the node sensitivity under different conditions, three different transducer designs were fabricated and tested for four different fluids, i.e., air, isopropanol, glycerin, and distilled water—achieving a sensitivity of 1.6965 +/− 0.2028 εr/pF. The use of laser ablation allowed the reduction of the transducer footprint while maintaining its sensitivity within an adequate value for the targeted applications.

Dual-Use Transducer for Ultrasound Imaging and Pulsed Focused Ultrasound Therapy.

Pulsed focused ultrasound (pFUS) uses short acoustic pulses delivered at low duty cycle and moderate intensity to noninvasively apply mechanical stress or introduce disruption to tissue. Ultrasound-guided pFUS has primarily been used for inducing cavitation at the focus, with or without contrast agents, to promote drug delivery to tumors. When applied in tandem with contrast agents, pFUS is often administered using an ultrasound imaging probe, which has a small footprint and does not require a large acoustic window. The use of nonlinear pFUS without contrast agents was recently shown to be beneficial for localized tissue disruption, but required higher ultrasound pressure levels than a conventional ultrasound imaging probe could produce. In this work, we present the design of a compact dual-use 1-MHz transducer for ultrasound-guided pFUS without contrast agents. Nonlinear pressure fields that could be generated by the probe, under realistic power input, were simulated using the Westervelt equation. In water, fully developed shocks of 42-MPa amplitude and peak negative pressure of 8 MPa were predicted to form at the focus at 458-W acoustic power or 35% of the maximum reachable power of the transducer. In absorptive soft tissue, fully developed shocks formed at higher power (760 W or 58% of the maximum reachable power) with the shock amplitude of 33 MPa and peak negative pressure of 7.5 MPa. The electronic focus-steering capabilities of the array were evaluated and found to be sufficient to cover a target with dimensions of 19 mm in axial direction and 44 mm in transversal direction.

Transfer matrix modeling on a longitudinal-bending coupled piezoelectric transducer with single-phase excitation: Analysis and verification.

Surface-bonded type piezoelectric transducers have the advantages of simple structure, easy miniaturization, and flexible designand have been widely employed as the stator of ultrasonic motors. In order to simplify the control system, a surface-bonded type single-phase excited piezoelectric transducer operating in the longitudinal-bending coupling vibration is proposed, modeled, and validated in this study. Using the asymmetrical excitation effect, the longitudinal-bending coupled vibration is generated in the proposed piezoelectric transducer only applied with a single-phase electrical signal, leading to the production of the elliptical motion at its driving tip. The proposed transducer holds the advantages of compact structure, simple control system, and low manufacturing costs. The transfer matrix method, which is an efficient and fast semi-analytic computation solution, is employed to develop a dynamic model for the proposed transducer in this study in order to provide a general modeling method for surface-bonded type piezoelectric transducers operating with the longitudinal-bending coupled vibration. A novel longitudinal-bending coupled vibration transfer matrix is created first for surface-bonded type piezoelectric composite element. Then, a general semi-analytical electromechanical coupling model is developed to analyze dynamic behaviors of the proposed piezoelectric transducer. Finally, experimental validation is carried out on the prototype of the proposed piezoelectric transducer and compared with the calculation results using the developed transfer matrix model. Experimental results matched well with the calculation results, which confirmed the correctness of the transducer designand verified the feasibility of the developed transfer matrix model. The proposed piezoelectric transducer presents the potential application for linear ultrasonic motors.

Computational analysis of the influence of the perforated plate on sandwich transducer in sound radiation performance

To improve the acoustic radiation performance of the sandwich transducer, a perforated plate is added to the radiation end of the transducer. The improved effect of the addition of a perforated plate on acoustic radiation performance of the transducer is studied. First, based on electromechanical equivalence principle, when a perforated plate is attached to a piston vibrator, the expressions of the vibration velocity of radiation surfaces, directivity index (DI) and radiated sound power are derived. Thus, the influences of the perforated plate on the sound radiation performance of the piston vibrator are analyzed. Then, the perforated plate is attached to the radiation surface of a sandwich transducer, and the electromechanical equivalent circuit of the transducer is established. Thus, the input impedance at the radiation end, vibration velocity and sound pressure level (SPL) of the transducer are derived. Further, the SPL of the transducer is calculated and the influences of the perforated plate on the transducer acoustic radiation performance with or without a matching layer are studied. And, the influences of the perforated plate on acoustic radiation performance of different operating frequency transducers are analyzed. Finally, the influences of the perforated plate structural parameters on the SPL of transducer are studied. The results show that the perforated plate with appropriate parameters could further improve the impedance matching between the input impedance and the radiation impedance at the radiation end of the transducer, thus the radiated SPL could be improved maximally. The research method is expected to applied in high-power transducer design.

Design of low-frequency broadband flextensional transducers based on combined particle swarm optimization and finite element method

For designing underwater acoustic transducers, it is usually very difficult and time-consuming to determine multiple parameters simultaneously. Therefore, a novel design method that combines the particle swarm optimization (PSO) and finite element method (FEM) is proposed for low-frequency broadband flextensional transducers (FTs). This method can optimize multiple structural dimensions simultaneously and maximize the bandwidth performance of FTs efficiently. The validity of the PSO-FEM approach was verified by the optimization design and experiments of a class IV FT. Compared with previously reported design methods of FTs, this method is more efficient and avoids tedious operations. This work also provides a powerful and handy tool for the design of other underwater acoustic transducers.

Analysis and Design of Single-Phase Unidirectional Transducers with High Directivity

Electrode-width-controlled (EWC) single-phase unidirectional transducers (SPUDT) contribute to reduction of insertion loss of surface acoustic wave (SAW) devices due to their strong unidirectional properties. In this work, we propose a method to optimize the unidirectionality of EWC-SPUDT based on our research results that the unidirectionality of the EWC-SPUDT cell is strongly related to its reflectivity and its unidirectional angle. Furthermore, in order to ensure strong unidirectionality to achieve low insertion loss, a simulator based on the finite element method (FEM) is used to study the relationship between geometrical configuration of the EWC-SPUDT cell and its reflection coefficient, as well as its transduction coefficient. Simulation results indicate that the reflection coefficient of the optimized EWC-SPUDT cell composed of 128° YX lithium niobite (LiNbO3) substrate and Al electrodes with thickness of 0.3μm reaches the optimal value of 5.17% when the unidirectional angle is designed to be −90°. A SAW delay line is developed with the optimized EWC-SPUDT cell without weighing, and the simulation results are verified by experiments. The experimental results show that the directivity exceeds 30 dB at the center frequency and the insertion loss is just 6.7 dB.

Inverse Design of Near-Field Transducer for Heat-Assisted Magnetic Recording Using Topology Optimization

Heat-assisted magnetic recording (HAMR) is one of the next generation technologies in data storage that can increase the areal density to beyond 1.5 Tb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Near-field transducer (NFT) is a key component of the HAMR system that locally heats the recording medium by concentrating light below the diffraction limit using surface plasmons. In this work, we use density-based topology optimization for inverse design of NFT for a desired temperature profile in the recording medium. We first perform an inverse thermal calculation to obtain the required volumetric heat generation (electric field) for a desired temperature profile. Then an inverse electromagnetic design of NFT is performed for achieving the desired electric field. NFT designs for both generating a small heated spot size and a heated spot with desired aspect ratio in recording medium are demonstrated.