Piezoelectric Composite Transducers Research Articles

Design, fabrication, and characterization of 1–3 piezoelectric composite air-coupled ultrasonic transducers with micro-membrane filter matching layer

Air-coupled ultrasonic transducers are widely used in various fields of nondestructive material characterization. This paper presents the fabrication and performance characterization of 1–3 piezoelectric composite air-coupled ultrasonic transducers operating at frequencies ranging from 400 kHz to 600 kHz. The transducers are fabricated using a dice-and-fill method with PZT-5 as the active material. A double-layer matching strategy is employed, utilizing hollow glass microsphere filled epoxy resin as the first matching and bonding layer. Additionally, micro-membrane filters with different pore sizes are used as the second matching layer. Thermoplastic adhesive TPU is utilized to bind the micro-membrane filter and the first matching layer. Due to the low acoustic impedance of the hollow glass microsphere filled epoxy resin and micro-membrane filter, acoustic impedance mismatch is reduced. Finite element simulation is used to determine the optimal ceramic volume fraction and ceramic pillar height of the 1–3 piezoelectric composites. When the pore size of the micro-membrane filter is 0.8 μm, the transducer achieves the lowest two-way insertion loss of −56.86 dB and the highest −6 dB bandwidth of 15.6 %, making it feasible for through mode applications.

Prediction of directivity characteristics of piezoelectric macro-fiber composite interdigital transducers: a semi-analytical approach

The employment of guided waves for structural health monitoring applications has attracted substantial attention in recent years. Piezoelectric transducers are frequently employed in these systems for elastic wave generation and acquisition. Their dynamic properties, i.e., direction-dependent frequency characteristics, are an important feature for designing a reliable monitoring strategy. Although analysis of the transducer directivity pattern can be performed using finite element models, these usually tend to be computationally very expensive, especially, for parametric and optimization studies. In this paper, a semi-analytical methodology is proposed that can predict the far-field responses of complex transducers of arbitrary shape and structure mounted on elastic plates. The approach reported here couples analytical far-field predictions with a local FE model evaluating the traction field generated by the transducer. Thus, the FE model captures the near-field responses, while the analytical part predicts the far-field responses. The implementation of this semi-analytical method requires development of analytical and numerical frameworks. The former includes computation of dispersion curves of the inspected plate, the stress and displacement profiles of wave modes and the excitability curves, while the latter includes estimation of the traction field between the transducer and the plate using the FE model. Owing to the popularity of piezoelectric macro-fiber composite (MFC) interdigital transducers, in this paper, we apply the proposed method to simulate the directivity patterns of the MFC IDTs of different configurations. To validate the reliability of the proposed method the simulated patterns are compared with experimental results obtained using Laser Doppler Vibrometer (LDV).

A High-Performance Flexible Hydroacoustic Transducer Based on 1-3 PZT-5A/Silicone Rubber Composite.

In recent years, hydroacoustic transducers made of PZT/epoxy composites have been extensively employed in underwater detection, communication, and recognition for their high energy conversion efficiency. Despite the ease with which these transducers can be formed into complex shapes, their lack of mechanical flexibility limits their versatility across various sizes of underwater vehicles. This study introduces a novel flexible piezoelectric composite hydroacoustic transducer (FPCHT) based on a 1-3 PZT-5A/silicone rubber composite and an island-bridge flexible electrode, which can break the limitations of existing hydroacoustic transducers that do not have flexibility. The finite element method is used to optimize the structural parameters of high-performance 1-3 FPC. A large-sized (187 mm × 47 mm × 5.12 mm) FPC is fabricated using an improved cutting-filling method and packaged into the FPCHT. Compared with the planar rigid PZT/epoxy composite hydroacoustic transducer (RPCHT) of the same size, the TVR (186.5 db) of the FPCHT has increased by about 7 dB, indicating that it has better acoustic radiation performance and electroacoustic conversion efficiency. Furthermore, its electroacoustic performance exhibits excellent stability under different bending states. Therefore, the FPCHT with high electroacoustic performance is an ideal substitute for the existing RPCHT and promotes the development of hydroacoustic transducers towards flexibility and portability.

BiScO3-PbTiO3 based high temperature piezoelectric ceramics composite ultrasonic transducer

Utilizing the electrical resonance method, matrices encompassing elastic, piezoelectric, and dielectric properties were calculated for 0.36BiScO3-0.64PbTiO3 (BSPT) ceramics. The design parameters for the BSPT/epoxy 2-2 composite material were meticulously elucidated through simulations conducted via COMSOL software. Characterization outcomes unveil that the synthesized composite material exhibits diminished acoustic impedance and heightened electromechanical coupling in comparison to its piezoelectric ceramic counterparts. Subsequent to the design and fabrication of ultrasonic transducers employing both BSPT ceramics and BSPT/epoxy 2-2 composite material, a thorough investigation into their electrical and acoustic attributes ensued at ambient temperature and 200 °C. Test results manifest that the BSPT/epoxy 2-2 composite high temperature ultrasonic transducer (CHTUT) demonstrates a center frequency and bandwidth of 4.52 MHz and 54.71%, respectively, at room temperature. While, at 200 °C, these parameters are 3.54 MHz and 80.79%. The HTUT, under parallel scrutiny, exhibits a center frequency and bandwidth of 4.65 MHz and 34.23% at room temperature, respectively, and 4.52 MHz and 29.65% at 200 °C. These findings prove the robust ultrasonic performance of the CHTUT, even under elevated temperatures, with the BSPT ceramic based counterpart demonstrating superior temperature stability. Furthermore, the results of an imaging experiment involving steel step blocks at both room temperature and 200 °C align consistently with the acoustic test outcomes.

Quantification of damage expansion influence on frequency response function of plate for structural health monitoring with integral differential method

This paper presents a feasibility study on damage size quantification throughout the damage expansion procedure using the integral differential method based on the developed frequency response function (FRF) programme. A designed pattern of piezoelectric Micro Fibre Composite (MFC) transducers was integrated with three composite panels for a real time monitoring testing by swept sine vibration input signals under three varied frequency bandwidths ranged from 10 to 1 kHz, 1k-3 kHz and 3k-5 kHz, respectively. The composite panels under pristine stage without any impact damages were tested and documented as a cross-reference for subsequent quantification estimation. The damages were introduced around transducers array, and its expansion process is equivalently simulated by a repetitive impact test procedure. A modified damage index, difference of response (DoR), was derived through integral differential method to assess the FRF outcome change of damaged composite plate relative to the pristine state. Combined with damage geometrical dimensions measured by thermography imaging technology, a quantification formula is derived reversely through numerical analysis, which showed a segmentation linear relation between the DoR and damage size governed by the power and logarithmic functions. The damages under different severity subjected to an additional composite plate were successfully quantified by the segmentation formula, which validate the feasibility of quantification with DoR.

A spiral slotted transducer with high longitudinal-torsional conversion rate

The longitudinal-torsional (L-T) composite piezoelectric transducer has wide applications in material processing, welding, and other fields due to its exceptional machining efficiency. This study introduces a spiral slotted L-T transducer, which is designed to achieve a high L-T conversion rate at low operating frequency. The equivalent spring concept is employed to derive the equivalent circuit of the L-T transducer, which provides a convenient study for the frequency characteristics of the transducer. A finite element model is developed to analyze the performance of the transducer and investigate the effect of the spiral slot parameters on the resonance frequency, amplitude, and the L-T conversion rate of it. Two prototype transducers are constructed and measured experimentally. Theoretical computation results, finite element simulation results, and experimental results are compared to each other. The comparison results demonstrate that the proposed computation model provides accurate prediction of the L-T coupling resonance frequency of the transducer. By adjusting the spiral slot parameters of the transducer, a higher L-T conversion rate can be achieved, which may have more applications in practical engineering.

Research on vibration characteristics of the longitudinal-radial composite piezoelectric ultrasonic transducer

The transducer with high power capacity and extensive radiating area is required in some industrial processes like ultrasonic sonochemistry, ultrasonic cleaning and ultrasonic defoaming and so on. In order to achieve the desired effects, the longitudinal-radial composite piezoelectric ultrasonic transducer is proposed in this paper. The transducer is composed of a longitudinal sandwich piezoelectric transducer, a stepped ultrasonic horn and a metal sphere. The longitudinal vibrations of the sandwich piezoelectric transducer and the stepped ultrasonic horn excite the radial vibration of the metal sphere so that the longitudinal-radial coupled vibration of the transducer is achieved. The equivalent circuits for a sphere in radial vibration and for the entire system in longitudinal-radial coupled vibration have been developed. To validate the proposed equivalent circuits, the vibration characteristics of the transducer are investigated using the equivalent circuit method, numerical method, and experiment. The resonance frequencies obtained from the equivalent circuit method, numerical method and experiment are 29992 Hz, 29990 Hz and 30590 Hz, respectively, and the simulated and experimental results indicate that the frequencies correspond to the designed longitudinal-radial coupled resonance mode of the transducer. The measured frequency and displacement distribution showed good agreement with the analytical and numerical calculation results.

Numerical Study of a Miniaturized, 1–3 Piezoelectric Composite Focused Ultrasound Transducer

This study aimed to develop an optimal methodology for the design of a miniaturized, 1–3 piezoelectric composite focused ultrasound transducer. Miniaturized focused ultrasound (FUS) devices, generally guided through catheters, have received considerable attention in the biomedical and ultrasound fields as they can overcome the technical restrictions of typical FUS transducers. However, miniaturized transducers cannot readily generate a high acoustic intensity because of their small aperture sizes and the vibration mode coupling. As such, 1–3 composite transducers, having a high electromechanical coupling and efficient vibration directivity, break through the current technical restrictions. However, the systematic methodology for designing miniaturized FUS transducers has not been thoroughly discussed so far. Therefore, in this study, we designed 1–3 piezoelectric composite transducers using analytical and numerical methods. Specifically, extensive parametric studies were performed through finite element analysis under the coupled field with piezoelectricity, structural vibration, and acoustic pressure. The simulation results confirmed that the optimal design of the 1–3 composite type transducer produces much higher (>160%) acoustic pressure output at the focal point than the single-phase device. Furthermore, the array type of the interstitial transducer was predicted to produce an unprecedented acoustic intensity of approximately 188 W/cm2 under a short duty cycle (1%). This study will provide valuable technical methodology for the development of interstitial, 1–3 composite FUS transducers and the selection of optimal design parameters.

Effect of Temperature on Ultrasonic Nonlinear Parameters of Carbonated Concrete.

In order to explore the monitoring technique of concrete carbonation in various temperatures, longitudinal ultrasonic nonlinear parameters of carbonated concrete are measured by using an embedded composite piezoelectric transducer (ECPT) and a surface-mounted transducer. The effect of temperature from -20 ∘C to 40 ∘C with a temperature interval of 5 ∘C and water-cement ratio on the measurements of ultrasonic parameters for carbonated concrete is investigated. The ultrasonic transmission detection method and the second harmonic generation (SHG) technique for longitudinal waves are used in the study. Results of the experiment demonstrate that ECPT is effective in the monitoring of the changes in ultrasonic parameters of carbonated concrete. At the temperature ranging from 15 ∘C to 40 ∘C, the increasing temperature slightly increases the relative nonlinear parameters of carbonated concrete. It decreases significantly that the relative nonlinear parameters of carbonated concrete measured at 0 ∘C compared with that at 10 ∘C. The configuration in this measurement is also appropriate for the assessment of carbonated concrete during carbonation time in low-temperature environments (below 0 ∘C). In the same carbonation time, the relative nonlinear parameters also increase slightly when the temperature is at -20 ∘C to 0 ∘C, but it does not change too much. Furthermore, there is a more significant variation of the nonlinear parameters in the same carbonation time for the specimens with a high water-cement ratio than that with a low one.

High-efficiency piezoelectric energy harvester for vehicle-induced bridge vibrations: Theory and experiment

Massive dissipated vibration energy of railway bridges is a sustainable energy source that can be harvested by piezoelectric energy harvesting technology. It provides a promising solution for powering bridge health monitoring systems. However, it remains challenging to achieve high energy output for the harvested energy to be of utility value. An efficient dynamic-magnified piezoelectric energy harvester (D-M PEH) is proposed, which reaches an energy output as high as 0.55 W under a harmonic acceleration excitation of unit amplitude and low frequency. The high energy output is achieved by incorporating a dynamic amplifier as well as several composite piezoelectric transducer cells (PT-cells) with d33-mode. The lumped parameters of the PT-cell are theoretically derived by considering the stacking deformation caused by the inverse piezoelectric effect. The energy harvesting performances of the D-M PEH are then investigated both theoretically and experimentally. When a train passes through the bridge, the maximum output voltage and power of the proposed D-M PEH can reach 603 V and 0.728 W, respectively. The output power is much higher than that of reported piezoelectric energy harvesters installed on railway bridges. The prototype system holds great potential to be part of the smart railway.

A Flexible Ultrasound Array for Local Pulse Wave Velocity Monitoring.

Pulse wave velocity (PWV) measured at a specific artery location is called local PWV, which provides the elastic characteristics of arteries and indicates the degree of arterial stiffness. However, the large and cumbersome ultrasound probes require an appropriate sensor position and pressure maintenance, introducing usability constraints. In this paper, we developed a light (0.5 g) and thin (400 m) flexible ultrasound array by encapsulating 1–3 composite piezoelectric transducers with a silicone elastomer. It can capture the distension waveforms of four arterial positions with a spacing of 10 mm and calculate the local PWV by multi-point fitting. This is illustrated by in vivo experiments, where the local PWV value of five normal subjects ranged from 3.07 to 4.82 m/s, in agreement with earlier studies. The beat-to-beat coefficient of variation (CV) is 12.0% ± 3.5%, showing high reliability. High reproducibility is shown by the results of two groups of independent measurements of three subjects (the error between the mean values is less than 0.3 m/s). These properties of the developed flexible ultrasound array enable the bandage-like application of local PWV monitoring to skin surfaces.

Characteristics of a 2-2 Piezoelectric Composite Transducer Made by Magnetic Force Assembly

A wider operational bandwidth, a higher electromechanical coupling factor, and lower acoustic impedance are important requirements for ultrasound transducers for use across many applications. Conventional 2-2 piezoelectric composite transducers have been widely researched because of their wider bandwidth and higher sensitivity over their piezoelectric ceramic counterparts. In this paper, the fabrication of a novel 2-2 piezoelectric composite using magnetic force assembly is proposed to explore the potential of the transducer and to minimize mode coupling effect compared to 1–3 composites. To determine the desired transducer performance, such as the electromechanical coupling factor, the operational bandwidth, and the acoustic impedance, the design of a 2-2 composite should be considered using the mode-coupling theory and an effective medium model. The experimental results indicate that the electromechanical coupling factor and the −6 dB fractional bandwidth of the composite achieve values of 0.58 and 65.2%, respectively, which are comparable to those of traditional 1-3 piezoceramic/epoxy composites.

Analytical modeling and experimental validation of a butterfly-shaped piezoelectric composite transducer

Analytical modeling and experimental validation of a butterfly-shaped piezoelectric composite transducer

The vibro-acoustic analysis of a matching layer attached on a 1–3 piezoelectric composite transducer

The vibro-acoustic analysis of a matching layer attached on a 1–3 piezoelectric composite transducer

Smart materials for ultrasonic piezoelectric composite transducer: A short review

At every step of development, advanced composite combinations are found, resulting in a material revolution. Smart materials, with their many classifications and characteristics, play an important part in today's research. The vast majority of dielectric, electro-magnetic, fatigue, and electric attributes were completely studied. These factors influence the working performance of piezoelectric composite materials. For various stiffness ratio the breakage point of the material changes does affects the fatigue cycle is explained. For ultrasonic transducer applications, we may design the structure to produce materials with better electromechanical coupling and lower acoustic impedance than traditional piezoelectric ceramics. The requirement for composites in piezoelectric transducers explains the high performance and high-end applications. The interaction of the main factors was displayed under various situations, majority of changes happens in the mechanical and chemical property changes and that can be recovered by treating the material and the results were explained.

Wireless Power Transmission for Implantable Medical Devices Using Focused Ultrasound and a Miniaturized 1-3 Piezoelectric Composite Receiving Transducer.

Wireless power transmission (WPT) using ultrasound is a promising way for wirelessly recharging implantable medical devices (IMDs). However, the transmitted power using ultrasound so far is insufficient for driving the existing IMDs. Moreover, the size of the receiving transducer is larger, which is not suitable for implantation. To increase the output power and reduce the size of the implantable receiver, this article presents a method of combining focused ultrasound with a miniaturized 1-3 piezoelectric composite receiving transducer to produce higher electrical power. An analytical fluid-structure interaction model is constructed to fully understand the operating mechanism of the receiving transducer under ultrasonic force. In our experiments, a miniaturized 1-3 piezoelectric composite receiving transducer with a diameter of 3.7 mm was used. The output power generated from the receiving transducer reached 60 mW at a distance of 150 mm. In vitro and in vivo animal experiments proved that the miniaturized transducer could successfully receive focused ultrasonic energy and convert it to electrical power. The method presented and the electrical power that we obtained can provide a valuable reference for wirelessly charging of IMDs.

Experimental validation of axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency

The axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency capability have been proposed by adjusting the external electric resistance and the ratio of piezoelectric layer numbers between the actuator part and the sensor part, which have promising potential in designing the novel cymbal transducer for underwater sound projector and ultrasonic radiator applications. In the previous studies, the multilayer models were established to guide the design of the transducers with arbitrary layer number, and analyzed the dynamic characteristics theoretically. In this work, an experimental study is performed to validate the theoretical models and predictions. Piezoelectric rings with multiple concentric annular electrodes are designed to characterize the multilayer piezoelectric composite cylindrical transducers. The top surface of the piezoelectric rings is divided into two separate parts. One part is covered by multiple concentric annular electrodes, corresponding to the piezoelectric layers, and the other part is uncovered, corresponding to the elastic layers. Four prototypes are fabricated and each consists of four concentric annular electrodes. The impedance spectra are measured by the impedance analyzer to obtain the resonance and anti-resonance frequencies. Effects of two adjusting methods on the dynamic characteristics are evaluated experimentally. The experimental results basically coincide with the theoretical ones. This comprehensive experimental work assures the feasibility of using axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequencies and confirms the benefit of the developed theoretical models for guiding the fabrication and optimization of this type of transducers.

Multifrequency ultrasonic transducers based on dual vibration and harmonic mode

Multifrequency ultrasonic transducers have broad application prospects in the field of biomedical due to their high imaging resolution and detection depth. This paper proposed a design method of triple frequency single-element transducers by finite element method(FEM). The triple frequency transducers are based on contour mode, thickness mode and the third harmonic of thickness mode. Nine micro single element transducers with different widths and matching layers were fabricated and characterized to verify the design method. The traditional 30 MHz single frequency transducer and 2.3 MHz 1–3 piezoelectric composite transducer were used to compare with high frequency part and low frequency part of the triple frequency transducers, respectively. The pulse-echo characteristics of the triple frequency transducers have impressive low and middle frequency part. The high frequency part is similar with traditional transducer except the sensitivity is 0.5 times. The results certify the feasibility of a triple-Frequency transducer based on dual vibration and harmonic modes.

Wideband and wide beam piezoelectric composite spherical cap transducer for underwater acoustics

A new class of piezoelectric composite spherical cap transducer that produces a wide beam and bandwidth was developed for underwater acoustics. A finite element analysis (FEA) simulation was used to design the transducer. Electroacoustic response measurements in water were made on a transducer to evaluate the performance characteristics and then compared with the FEA results. The measured results show the transducer can provide a 112° beamwidth and a usable frequency band from 215 kHz to 355 kHz. The maximum transmitting voltage response (TVR) of the transducer is 161.7 dB re 1µPa/V@1m at 255 kHz.

Theoretical calculation model of emission performance for 1-3 piezoelectric composite transducer

1-3 piezoelectric composite has been widely used in underwater acoustic high frequency transducer because of its excellent high frequency characteristics. Resonance frequency, transmitting voltage response and bandwidth are three key parameters to measure the emission performance of 1-3 piezoelectric composite transducer. In order to predict these parameters, the theoretical model of 1-3 piezoelectric composite transducer is established based on the electromechanical equivalence principle and acoustic field theory. According to the theoretical model, numerical calculation method is used to calculate the emission performance parameters of the transducer. The theoretical calculation agrees well with the experiment, and the maximum error is less than 7.9%. It shows that the theoretical model established in this paper is reasonable and can accurately predict the emission performance of 1-3 piezoelectric composite transducer.