High-power Transducer Research Articles

A longitudinal-torsional mode ultrasonic needle for deep penetration into bone

This work presents a longitudinal-torsional (L-T) composite mode ultrasonic needle device for deep bone penetration. The L-T needle is a geometrically modified version of an L-mode needle whose efficacy as a prototype ultrasonic bone biopsy device has been previously demonstrated by the authors. Finite element analysis (FEA) aided in the design of the L-T needle, with the aim of maximising the achievable torsional displacement while matching the longitudinal displacement achieved by the L-mode needle. Experimental modal analysis (EMA) of the fabricated ultrasonic device was used to identify the modal parameters and validate the FEA model. Harmonic analysis then provided an insight into how the inherent nonlinearities of the high-power transducer are affected by incorporating the geometrical features that degenerate the L mode into an L-T mode. High power characterisation shows that the longitudinal displacement amplitude of the L-T mode needle is larger than that of the L-mode needle. Comparative penetration tests in fresh Wistar rat skull were evaluated by investigating cell death and cell survival. The region of statistically significant cell death was small for both devices, with the combined axial and shear motion of the L-T device causing increased osteocyte necrosis within this region. Nevertheless, the results suggest a promising environment for post-operative healing. It is shown how this technology offers a potential technique for a surgical approach to the petrous apex, an application that requires a deep penetration into bone.

FEM-based time-reversal technique for an ultrasonic cleaning application

Ultrasound provides a way to clean fouled pipes in industrial settings without interrupting the production. Ultrasonic clamp-on cleaners are used to clean pipes, but they typically cannot focus the cleaning power. This leads to insufficient cleaning results in cases where the fouling is localized to certain parts of the pipe.To solve this issue, we propose a finite-element method -based time-reversal (FEM-TR) technique for controlling the acoustic field produced by an ultrasonic clamp-on cleaner. We demonstrate by simulations and experimental validation that FEM-TR can be used to control the acoustic field in clamp-on cleaners featuring relatively few narrow-band and high-power transducers. The proposed method allows us to focus sound to arbitrary pre-selected locations inside the structure.

High-Pressure Low-Frequency Lateral Mode Phased-Array Transducer System for the Treatment of Deep Vein Thrombosis: An In Vitro Study.

Deep vein thrombosis (DVT) can lead to a fatal disease known as pulmonary embolism. Application of high-power ultrasound has been successful in studies to mechanically fragment the clots. Single-element ultrasound transducers were used in most of the studies. Challenges associated with phased arrays, such as high electrical impedance and element breakdown at high voltages, were addressed in the previous study, and a high-power 64-element transducer module was designed and fabricated. In this study, a cylindrical array of 16 modules with the frequency of 260 kHz was modeled and constructed for DVT thrombolysis. The maximum pressure, focal size, and steering ability of the array were examined. In vitro experiments were conducted to assess the performance of the array. The simulated pressure amplitude of 34 MPa at the depth of 55 mm (average femoral vein (FV) distance from the inner surface of the thigh) was in consistent with the experiments and satisfied the purpose of this study. Moreover, the employed module distribution resulted in a focal spot dimension of 2.4×2.8×7.3 mm3 (at the 75% pressure amplitude level) that can be confined in a human FV with the average diameter of 12 mm. In vitro experiments manifested a partial and complete clot breakdown at 11.5- and 15-MPa pressure at the focus. The design and engineering of the array system was succeeded in maintaining the desired pressure and focal size even when steered. The results presented in this study suggest the potential of the designed array system for clinical applications.

SPICE Modeling of a High-Power Terfenol-D Transducer Considering Losses and Magnetic Flux Leakage.

Of great importance is modeling for transducer design and application to predict its performance and simulate key characteristics. The equivalent circuit modeling (ECM), one of the most powerful tools, has been widely used in the transducer industry and academia due to its outstanding merits of low simulation cost and easy usage for multi-field simulation in both time and frequency domains. Nevertheless, most of the existing equivalent circuit models for Terfenol-D transducers normally ignore three material losses, namely elastic loss, piezomagnetic loss, and magnetic loss. Additionally, the magnetic leakage due to the intrinsic poor magnetic permeability of Terfenol-D is rarely considered into the piezomagnetic coupling. Both loss effects will produce substantial errors. Therefore, an improved SPICE model for a high-power Terfenol-D transducer considering the aforementioned three losses and magnetic flux leakage (MFL) is proposed in this article, which is implemented on the platform of LTspice software. To verify the usefulness and effectiveness of the proposed technique, a high-power Terfenol-D tonpilz transducer prototype with a resonance frequency of around 1 kHz and a maximum transmitting current response (TCR) of 187.1 dB/1A/ μ Pa is built and tested. The experimental results, both in the air and water of the transducer, are in excellent agreement with the simulated results, which well validates our proposed modeling methods.

Theoretical and Empirical Verification of Electrical Impedance Matching Method for High-Power Transducers

In our prior study, a systematic approach was used to devise Langevin transducers for high-power applications where the energy efficiency was not considered in the design criteria. In this paper, the impedance matching methods are thus proposed to evaluate what matching topology is appropriate for their use. Both the series inductor scheme and low pass filter composed of a series inductor and shunt capacitor are examined as matching circuits. According to MATLAB simulation, the resonance frequency is seen at 36.79 kHz due to a series L circuit, and its associated impedance is reduced by 70.45% from that of its non-matching condition. The measured resonance frequency is 36.77 kHz and the corresponding impedance is decreased by 59.52%. Furthermore, the acoustic pressure is measured to determine the effect of the matching circuit on the transducer’s actual behavior. The transducer with a series L circuit shows more efficient matching results, 2.28 kPa of positive acoustic pressure is emitted without matching and 3.35 kPa is emitted with a series L element, respectively. As a result, this study demonstrates how to evaluate the influence of matching circuits by using our customized approach rather than commercial SPICE programs, as well as how to experimentally verify the acoustic behavior of high-power Langevin transducers.

Loss Characterization of Giant Magnetostrictive Material Under Compressive Stress

The properties of giant magnetostrictive material (GMM) are very sensitive to external compressive stress. Knowledge of these key properties is of essential importance in practical applications such as high-power underwater transducers. Although the parameters of GMM have been extensively studied, characterization and analysis of magnetic, elastic, and piezoelectric losses under different compressive stresses are rarely reported due to the difficulty in experimentally realizing the ideal mechanical free or clamped boundary conditions. In this study, we designed a longitudinal transducer for complex parameters characterization of GMM. We successfully characterize the key three losses in GMM using a multi-degree-of-freedom (MDOF) lumped parameter equivalent circuit model (LECM), meticulously incorporating the surface contact damping, stiffness, and structural losses. MDOF LECM provides a novel idea for loss characterization of GMM under compressive stress. In contrast to prior-art parameters characterization based on the distributed parameter equivalent circuit model (DECM), the proposed characterization based on MDOF LECM shows apparent superiority in terms of global sensitivity. The intensive losses of GMM for ten-time characterizations show high stability and are all positive. Statistical analysis of intensive losses’ dependency on the compressive stress is performed. A longitudinal transducer is designed for experimental verification. Finally, 95% prediction and confidence intervals for the variation trend of the intensive losses in relationship with compressive stress are obtained.

Study on heat pipe heat dissipation of high-power ultrasonic transducer

In order to solve the problems of frequency shift, efficiency decline and life shortening caused by temperature rise in the working process of high-power ultrasonic transducer, the technology of heat pipe is employed for enhancing heat dissipation of the ultrasonic transducer. A new type of high-power transducer with heat pipe heat dissipation (HPUT) is proposed in this study. The heat pipe radiator adopts the form of a copper–water-composite wick, and installs straight fins on the condensation section to enhance heat dissipation. Six heat pipe radiators are embedded in the front cover plate of the transducer close to the piezoelectric ceramic and evenly arranged along the circumference of the transducer. The vibration characteristics, radiated sound field characteristics and heat dissipation characteristics of the HPUT are compared with those of traditional Langevin ultrasonic transducer (TLUT) through simulations and experiments. Results manifest that compared with the TLUT, the HPUT has much lower operation temperature (reduced by 60% in this study), much smaller resonant frequency shift (reduced by 75% in this study) and the higher vibration amplitude (increased by 25% in this study). This study will contribute to the development of high-power ultrasonic transducer which has potential application value in many industrial fields.

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.

A Novel Coupled Piezoelectric Micromachined Ultrasonic Transducer Based on Piston Mode.

This article presents a piezoelectric micromachined ultrasonic transducer (pMUT) modified with a piston diaphragm term as piston diaphragm pMUT (PD-pMUT). The transmission sound pressure level (SPL) and the frequency bandwidth of the modified transducer can be remarkably improved by adding a piston diaphragm on the central circular diaphragm. In this work, a lumped model, an acoustic resonance model, and an equivalent circuit model are established to study the multiresonance mechanism. The second resonance peak is contributed by the interference acoustic wave generated between the circular and piston diaphragms. This work demonstrated a simulated far-field average SPL up to 132.2 dB in the single modified piston diaphragm structure and a 28.1%-6-dB frequency bandwidth by theoretical analysis and parameter optimization. The bandwidth is 3.31 times of the traditional pMUT with aluminum nitride (AlN) in air. In addition, the PD-pMUT has a -6-dB frequency bandwidth of up to 66%, which is 1.4 times of traditional pMUT in the liquid-coupled operation. The proposed PD-pMUT provides a new approach for the application of high transmission power and broad bandwidth transducers.

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.

"HIFU Beam:" A Simulator for Predicting Axially Symmetric Nonlinear Acoustic Fields Generated by Focused Transducers in a Layered Medium.

"HIFU beam" is a freely available software tool that comprises a MATLAB toolbox combined with a user-friendly interface and binary executable compiled from FORTRAN source code (HIFU beam. (2021). Available: http://limu.msu.ru/node/3555?language=en). It is designed for simulating high-intensity focused ultrasound (HIFU) fields generated by single-element transducers and annular arrays with propagation in flat-layered media that mimic biological tissues. Numerical models incorporated in the simulator include evolution-type equations, either the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation or one-way Westervelt equation, for radially symmetric ultrasound beams in homogeneous and layered media with thermoviscous or power-law acoustic absorption. The software uses shock-capturing methods that allow for simulating strongly nonlinear acoustic fields with high-amplitude shocks. In this article, a general description of the software is given along with three representative simulation cases of ultrasound transducers and focusing conditions typical for therapeutic applications. The examples illustrate major nonlinear wave effects in HIFU fields including shock formation. Two examples simulate propagation in water, involving a single-element source (1-MHz frequency, 100-mm diameter, 90-mm radius of curvature) and a 16-element annular array (3-MHz frequency, 48-mm diameter, and 35-mm radius of curvature). The third example mimics the scenario of a HIFU treatment in a "water-muscle-kidney" layered medium using a source typical for abdominal HIFU applications (1.2-MHz frequency, 120-mm diameter, and radius of curvature). Linear, quasi-linear, and shock-wave exposure protocols are considered. It is intended that "HIFU beam" can be useful in teaching nonlinear acoustics; designing and characterizing high-power transducers; and developing exposure protocols for a wide range of therapeutic applications such as shock-based HIFU, boiling histotripsy, drug delivery, immunotherapy, and others.

A high frequency, power, and efficiency diaphragm acoustic-to-electric transducer for thermoacoustic engines and refrigerators.

A high frequency, power, and efficiency diaphragm transducer is described for use with thermoacoustic engines and refrigerators. It uses a tube acting in compression and extension as the primary spring so that the mechanical resonant frequency is around 500 Hz. A high-frequency transducer results in more compact and higher power density thermoacoustic engines, refrigerators, and heat pumps. The tube spring furthermore constitutes a part of the pressure vessel so that the alternator is outside the pressure vessel, thereby simplifying transducer construction and reducing mass. The hermetically sealed transducer operates entirely without wear or lubricants, leading to a long maintenance-free lifetime. We present in situ efficiency measurement results at the full power operating frequency and temperature of the transducer. Despite the high operating frequency, the transducer efficiency is better than that of other transducers previously used in thermoacoustic systems. Accelerated fatigue test results on tube spring coupons justify the long-life claims. The exceptional stiffness of the primary spring in this transducer leads to the unusual need to consider stretch in additional transducer structural components. We present a multi-mass, lumped-element, coupled oscillator model of the transducer and discuss thermoacoustic system design using this model.

Large polarization and record-high performance of energy storage induced by a phase change in organic molecular crystals.

Dielectrics that undergo electric-field-induced phase changes are promising for use as high-power electrical energy storage materials and transducers. We demonstrate the stepwise on/off switching of large polarization in a series of dielectrics by flipping their antipolar or canted electric dipoles via proton transfer and inducing simultaneous geometric changes in their π-conjugation system. Among antiferroelectric organic molecular crystals, the largest-magnitude polarization jump was obtained as 18 μC cm−2 through revisited measurements of squaric acid (SQA) crystals with improved dielectric strength. The second-best polarization jump of 15.1 μC cm−2 was achieved with a newly discovered antiferroelectric, furan-3,4-dicarboxylic acid. The field-induced dielectric phase changes show rich variations in their mechanisms. The quadruple polarization hysteresis loop observed for a 3-(4-chlorophenyl)propiolic acid crystal was caused by a two-step phase transition with moderate polarization jumps. The ferroelectric 2-phenylmalondialdehyde single crystal having canted dipoles behaved as an amphoteric dielectric, exhibiting a single or double polarization hysteresis loop depending on the direction of the external field. The magnitude of a series of observed polarizations was consistently reproduced within the simplest sublattice model by the density functional theory calculations of dipole moments flipping over a hydrogen-bonded chain or sheet (sublattice) irrespective of compounds. This finding guarantees a tool that will deepen our understanding of the microscopic phase-change mechanisms and accelerate the materials design and exploration for improving energy-storage performance. The excellent energy-storage performance of SQA was demonstrated by both a high recoverable energy-storage density Wr of 3.3 J cm−3 and a nearly ideal efficiency (90%). Because of the low crystal density, the corresponding energy density per mass (1.75 J g−1) exceeded those derived from the highest Wr values (∼8–11 J cm−3) reported for several bulk antiferroelectric ceramics , without modification to relaxor forms.

New insights into the mechanical pre-stressing of piezotransducers

Although pre-stressing is a requirement for the operation of a high-power piezo transducers, its impact on the model, the performance and the design of such devices is still not yet fully covered in the literature. This work attempts to bridge this gap by analyzing how the components of the Butterworth-Van Dyke model, the resonances, electrical impedances, electromechanical coupling factor, mechanical losses, and the tuning inductance are determined as a function of mechanical pre-stress. We have employed the Butterworth Van-Dyke model to study piezoelectric transducers tightened with a range of pre-stressing levels (12.2–60.1 MPa). As expected, the experimental results indicate that the components of the Butterworth-Van Dyke model are dependent upon the mechanical pre-stressing. The conclusions point out that, under mechanical pre-stressing levels between a threshold value and 60.1 MPa, the transducers used in this work tend to stabilize and enhance their performances. Also, upon stabilization, the transducers can be tuned with a constant inductance, which may also aid the design of ultrasonic systems. Overall, this work contributes to the definition of pre-stressing levels and its relationship with the length of the transducer, the mechanical losses, and the tuning.

The temperature rise characteristics analysis and experiment of GMA

The giant magnetostrictive actuator (GMA) with giant magnetostrictive material (GMM) as the core component has wide applications in the field of precision drive and control. In this paper, through the analysis of the GMA coil, the loss and temperature rise characteristics of the GMA have been studied. Then, COMSOL Multiphysics software has been used to model the heat source distribution of the GMM actuator, and the factors affecting the working temperature of the GMM rod have been analyzed. Finally, based on the use requirements of the GMA, magnetic field, and internal temperature distribution characteristics, the heat dissipation scheme of the coil is proposed, and the experimental platform of the GMA with a thermal compensation function is built to verify the temperature characteristics and thermal compensation effect. Studying the internal temperature distribution law of the GMA not only has a guiding significance for the temperature control of the actuator and the design of the cooling system but also reduces the influence of the coil thermal effect on the performance of the transducer and lays the foundation for making full use of the GMM’s potential in high-power transducers.

Relationship between composition and electromechanical properties of CuO-doped textured PYN-PMN-PT ceramics

This study reports the effects of composition and the presence of residual template particles on the electromechanical properties of random and textured CuO-doped Pb(Yb1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics. Fully textured PYN-PMN-PT ceramics were produced with [001]-oriented barium titanate (BT) particles. The strain of all textured compositions was improved by 40–82 %, and the coercive field was increased by −1 kV/cm relative to ceramic compositions. Textured 20PYN-46PMN-34PT ceramics had the best combination of properties including a high Ec of 9.8 kV/cm and a low strain hysteresis of 8.5 %. Rayleigh analysis of textured PYN-PMN-PT ceramics showed that more rhombohedral compositions have greater strain because of improved extrinsic and intrinsic contributions to the piezoelectric response. These results demonstrate that textured PYN-PMN-PT is a promising material for high power transducers, however compositions must be sufficiently on the rhombohedral side of the morphotropic phase boundary to compensate for the phase-shifting effects of residual stresses from residual BT template particles.

Variable Coefficient Magnetic Energy Losses Calculation Model for Giant Magnetostrictive Materials

Accurate calculation of magnetic energy losses for magnetostrictive material is a necessary step in designing high-power magnetostrictive transducer. In this article, based on the losses separation formula and measured data of Terfenol-D, the changing trends of the losses coefficients are investigated. An improved magnetic energy losses calculation method with variable coefficients is established. The measured and calculated values of magnetic energy losses at different frequencies and flux densities of driving magnetic field are compared and analyzed. The results show that the calculation method can accurately calculate the magnetic energy losses at higher frequencies (1-20 kHz). The average error between the calculated and the measured values is 4.32%. This research can provide theoretical and experimental guidance for the higher frequency applications of magnetostrictive materials.

Textured Mn-doped PIN-PMN-PT Ceramics: Harnessing Intrinsic Piezoelectricity for High-power Transducer Applications

Mn-doped PIN-PMN-PT ceramics were 90% [001]C textured by reactive templated grain growth (RTGG) with 5 vol% BaTiO3 microplatelets. Hardened properties such as high coercive field (EC) of 14 kV/cm, low dielectric loss (tan δ) of 0.37-0.66%, and high QM of 496 were obtained. Textured Mn-doped ceramics have TC of 219 °C, and a two times greater low-field d33* of 846 pm/V than random ceramics. Rayleigh analysis of textured PIN-PMN-PT ceramics shows that Mn-doping reduces the relative extrinsic contribution of the piezoelectric response to the strain behavior from 38% to 18% (at 4 kV/cm) by reducing irreversible domain wall motion. Mn-doping also reduced the overall strain response of PIN-PMN-PT, but crystallographic texturing increased the intrinsic piezoelectric response of the lattice as evidenced by the increase in d33 (Berlincourt) from 283 pC/N in random ceramics to 341 pC/N in textured ceramics. These results demonstrate that textured Mn-doped PIN-PMN-PT ceramics are excellent candidates for high-power transducer applications.

High-Power Phased-Array Transducer Module for the Construction of a System for the Treatment of Deep Vein Thrombosis.

Blood clot can be disintegrated by high-intensity focused ultrasound alone through inertial cavitation. There are limitations in using single-element ultrasound transducers for this purpose such as lack of steerability and control of the focus in terms of shape and location. Phased-array transducers being able to rapidly scan over the clots can alleviate this problem. A full 3-D control of the ultrasound beam can be achieved by 2-D electronically steerable arrays. However, the required high-pressure amplitude has not been possible with such arrays. In this work, a 2-D 64-element fully populated phased-array transducer module was designed and fabricated for the high-pressure amplitude required for deep vein thrombosis (DVT). Lateral coupling was considered for the transducer design to decrease the electrical impedance and eliminate the need for electrical matching circuit. PZT-4 with a thickness of 0.35 mm, an element surface area of [Formula: see text] mm, and a length of 6 mm showed a mean electrical impedance of 60.4 ± 11.5 measured for each transducer element facilitating effective electric power transfer from the driving electronics. No breakdown was observed when the voltage was increased gradually to 180 ± 3 Vpp. Operation at 180 Vpp was found to be safe over 10,000 repetitions without reduction in the power, resulting in the average pressure amplitude of 1.01 ± 0.09 MPa at 2 mm from the element surface. These pressure amplitude values indicate that an array of eight modules (80 [Formula: see text] mm) is required to reach to the pressure amplitude needed for DVT. Such arrays are practical with the current technology.

The electro-acoustic output behavior and thermal stability of 1–3 piezoelectric composite transducers applied to FUS surgery

For 1–3 piezoelectric composite high-power transducers applied to FUS surgery, avoiding the electro-acoustic output performance fluctuating with the temperature is an important task. In this work, 1–3 type piezocomposites were fabricated with dice and fill method. The PZT4 piezoceramic was used as active phase, and mica powder modified epoxy resin E51 was used as passive phase: the mass ratio of the epoxy and mica powder was 10:x. Those composites were evaluated for power transducer applications with air backing and without front layer. The effect of mica powder modified polymer filler on the electro-acoustic output behavior and thermal stability of the transducer were detailed investigated. The results show that mica power could increase the storage modulus and the toughness of the polymer. As a result, an elevated kt of 0.7 was observed when the adding amount was 50 wt%. The electro-acoustic conversion efficiency (ηea) of the transducer substantial increased to 81–83% and with good thermal stability when x = 1–5. The research results show that adding mica powder in the filler materials was one of the potential methods to prepare high-power piezocomposite transducer.