Piezoelectric Composite Transducers Research Articles

Investigation of piezoelectric composite transducer in ultrasonic monitoring of cement hydration

Ultrasonic receiving transducers were fabricated by using 1–3 type cement/polymer based piezoelectric composites as sensing elements and a mixture of cement and epoxy resin as packaging material. An electromagnetic shielding coating material was used as a shielding layer. Based on the ultrasonic wave technique, the hydration reaction processes of Portland cement pastes with various water-to-cement ratios (w/c = 0·28, 0·40 and 0·50) were monitored by using the ultrasonic transducers. Performance analysis of the transducers showed that the shielded transducer has characteristics of a high signal-to-noise ratio, large head wave amplitude and a clear waveform. The head wave amplitude of the shielded transducer was 73% greater than that of the unshielded transducer, and the amplitude ratio of the head wave to the second wave of the shielded transducer was also increased (by 46%). The relationship between waveform and the wave parameters of the received ultrasonic wave and cement hydration reaction time was analysed. It was found that the cement hydration reaction process can be divided into different periods. The wave velocity in the cement paste is sensitive to w/c ratio, and increases with the progress of cement hydration reaction as well as the compressive strength. This was confirmed by the micro-morphology of the cement paste at various periods.

Phantom evaluation of stacked-type dual-frequency 1–3 composite transducers: A feasibility study on intracavitary acoustic angiography

In this paper, we present phantom evaluation results of a stacked-type dual-frequency 1–3 piezoelectric composite transducer as a feasibility study for intracavitary acoustic angiography. Our previous design (6.5/30MHz PMN–PT single crystal transducer) for intravascular contrast ultrasound imaging exhibited a contrast-to-tissue ratio (CTR) of 12dB with a penetration depth of 2.5mm. For improved penetration depth (>3mm) and comparable contrast-to-tissue ratio (>12dB), we evaluated a lower frequency 2/14MHz PZT 1–3 composite transducer. Superharmonic imaging performance of this transducer and a detailed characterization of key parameters for acoustic angiography are presented. The 2/14MHz arrangement demonstrated a −6dB fractional bandwidth of 56.5% for the transmitter and 41.8% for the receiver, and produced sufficient peak-negative pressures (>1.5MPa) at 2MHz to induce a strong nonlinear harmonic response from microbubble contrast agents. In an in-vitro contrast ultrasound study using a tissue mimicking phantom and 200μm cellulose microvessels, higher harmonic microbubble responses, from the 5th through the 7th harmonics, were detected with a signal-to-noise ratio of 16dB. The microvessels were resolved in a two-dimensional image with a −6dB axial resolution of 615μm (5.5times the wavelength of 14MHz waves) and a contrast-to-tissue ratio of 16dB. This feasibility study, including detailed explanation of phantom evaluation and characterization procedures for key parameters, will be useful for the development of future dual-frequency array transducers for intracavitary acoustic angiography.

Research of Ultrasound-Mediated Transdermal Drug Delivery System Using Cymbal-Type Piezoelectric Composite Transducer

Transdermal drug delivery (TDD) implemented by especially low-frequency ultrasound is generally known as sonophoresis or phonophoresis which has drawn considerable wide attention. However, TDD has not yet achieved its full potential as an alternative to conventional drug delivery methods due to its bulky instruments. In this paper, a cymbal-type piezoelectric composite transducer (CPCT) which has advantages over a traditional ultrasound generator in weight, flexibility, and power consumption, is used as a substitute ultrasonicator to realize TDD. First, theoretical research on a CPCT based on the finite element analysis was carried out according to which a series of applicable CPCTs with bandwidths of 20 kHz to 100 kHz were elaborated. Second, a TDD experimental setup was built with previously fabricated CPCTs aimed at the administration of glucose. Finally, the TDD performance of glucose molecule transport in porcine skin was measured in vitro by quantifying the concentration of glucose, and the time variation curves were subsequently obtained. During the experiment, the driving wave form, frequency, and power consumption of the transducers were selected as the main elements which determined the efficacy of glucose delivery. The results indicate that the effectiveness of the CPCT-based delivery is constrained more by the frequency and intensity of ultrasound rather than the driving waveform. The light-weight, flexibility, and low-power consumption of a CPCT can potentially achieve effective TDD.

Preparation and Properties of 1-3 Piezoelectric Composite Transducers

This study demonstrated the preparation of 1-3 piezoelectric composite transducers by using 1-3 piezoelectric composites as the active phases, air as the backing layer and polyurethane as the matching layer. The composite electrode was produced by electroless nickel coating and the effect of the matching layer on transducer performance was investigated in detail. The results showed that the matching layer could improve the receiving sensitivity of the transducer significantly. The receiving response value of the transducer at first increased and then decreased with the increase of the matching layer thickness. This receiving response had the largest head-wave amplitude value when the thickness of the matching layer was about 2.2 mm, which was in good agreement with the theoretical value. The resonance frequency of the transducer in water showed a tendency of low frequencies, and the bandwidth of the transducer in water became much wider than that in air. The reasonable matching layer could improve performance of the transducer effectively.

Simulation of 1-3 Piezoelectric Composite Cylindrical Transducer

A cylindrical transducer consisting of 1-3 piezoelectric composite was designed. Several rectangular bar elements were arrayed and adhered on the cylindrical backing to become a tubular transducer. The elements were 1-3 piezoelectric ceramic/polymer composites. The lumped characteristic parameters of 1-3 piezoelectric composite were obtained according to Smith's model. Two type models of transducer were established and simulated by ANSYS. One model was same to the actual transducer element. The other was an approximate element of the piezoelectric tube by using the lumped characteristic parameters. The radial vibration mode of two type models was analyzed. The simulation results indicated that the frequency of transducer were respectively 8.9 kHz and 8.7 kHz under radial vibration mode. The relative deviation in two type models is less than 2%.

High temperature, high power piezoelectric composite transducers.

Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

Design of micromachined self-focusing piezoelectric composite ultrasound transducer.

Based on the Fresnel half-wave band interference, a micromachined self-focusing piezoelectric composite ultrasound transducer was proposed in this paper. The theoretical analysis was deduced based on the concept of constructive interference of acoustic waves and electromechanical response of piezoelectric composites. The calculated and simulation results showed that it combined the advantages of composite transducer and plate self-focusing transducer, and can achieve high electromechanical coupling coefficient, low acoustic impedance, high intensity, short focal length and micro size. Because it was based on the micro-electromechanical systems, the fabrication process was accurate and controllable, which made it have good potential for interventional ultrasound imaging, cellular microstructure imaging, skin cancer detection and industrial nondestructive testing applications.

Cymbal Piezoelectric Composite Transducer for Soccer Robot Attitude Detection Application

This paper proposed a soccer robots attitude detection method based on the principle and vibration mode of cymbal piezoelectric composite transducer. Cymbal piezoelectric composite transducers and MEMS-based three-axis low-g sensor were set on some different support points of soccer robot's joint to accomplish attitude detection. The signal processing circuit and algorithm software were designed. The research results showed that the performance parameters of the soccer robot falling down attitude detection system based on cymbal piezoelectric composite transducer are better than the other sensor, such as the sensitivity, correct, undetected fall and stability duration, etc. The experiment results showed that the detection accuracy for falling down of the soccer robot can be 98% and the stability duration can be 60 minutes.

Study on Novel Relaxor Ferroelectric Single Crystal PMNT/Epoxy Composite Transducer Array

Using relaxor ferroelectric single crystals PMNT as piezoelectric phase and epoxy resin as a non-piezoelectric phase material, the piezoelectric composite is fabricated with the cutting - filling method. Using the same micro-structure parameters and the same process, the piezoelectric composite is prepared with the conventional piezoelectric ceramic PZT5 as piezoelectric phase material. The transducer array is respectively assembled with the PMNT /epoxy composites and PZT5/epoxy piezoelectric composite materials. Experimental results show that the relaxor ferroelectric single crystals PMNT / epoxy composite transducer array has higher sensitivity and less resonant impedance than PZT5/epoxy piezoelectric composite transducer array.

Modeling of Strain Energy Harvesting in Pneumatic Tires Using Piezoelectric Transducer

ABSTRACT This paper presents an evaluation study of the feasibility of harvesting energy from rolling tire deformation and using it to supply a tire monitoring device installed within the tire cavity. The developed technique is simulated by using a flexible piezoelectric fiber composite transducer (PFC) adhered onto the tire inner liner acting as the energy harvesting element for tire monitoring systems. The PFC element generates electric charge when strain is applied to it. Tire cyclic deformation, particularly at the contact patch surface due to rolling conditions, can be exploited to harvest energy. Finite element simulations, using Abaqus package, were employed to estimate the available strain energy within the tire structure in order to select the optimum location for the PFC element. Experimental tests were carried out by using an evaluation kit for the energy harvesting element installed within the tire cavity to examine the PFC performance under controlled speed and loading conditions.

Micromachining techniques in developing high-frequency piezoelectric composite ultrasonic array transducers

Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 μm in size with 5-μm kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm(2) with a 16-μm kerf between elements. The active piezoelectric material is (1 - x) Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT)/epoxy 1-3 composite with a PMN-PT pillar lateral dimension of 8 μm and an average gap width of ~4 μm, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse-echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the -6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about -33 dB. The techniques described herein can be used to build larger arrays containing smaller elements.

Defect sensitivity of piezoelectric strip transducers based on planar Lamb waves

Long narrow piezoelectric fiber composite transducers that can generate planar ultrasonic guided waves are investigated for damage detection in plates. These strip transducers function well as actuators because the ultrasonic energy does not spread out and the signal remains strong. However, their suitability as sensors must be investigated because the received signal is integrated over the entire length of the transducer, potentially making them less sensitive to localized damage since the voltage is averaged over the length of the sensor. A segmented sensing scheme is introduced here and studied both numerically and experimentally. The strip transducer is subdivided into n segments, where n varies from 1 to 11, and the sensitivity to a through-thickness slot is assessed. The results indicate that there is a considerable improvement in defect sensitivity provided by segmented sensing. For a 130-mm-long strip transducer and a 15-mm-long slot, the transmission coefficient decreased from 0.86 to 0.70 to 0.59, while the reflection factor increased from 0.05 to 0.30 to 0.36 for the full 130-mm strip, a 31-mm-long segment, and a 7-mm-long segment, respectively.

Study of Cymbal Piezoelectric Composite Transducer Based on Finite Element Analysis

A cymbal piezoelectric composite transducer (CPCT) has been developed in recent years, which converts small radial deformation into larger longitudinal deformation. In this paper, the finite element analysis (FEA) method is used to analyze the characters of CPCT, by which the optimized CPCT has been made. Firstly, the FEA theory of a CPCT has been described, and the two-dimensional FEA model of a CPCT has been established by ANSYS. Secondly, the simulation and analysis about the relationships between structural parameters and displacement have been carried out, by which the CPCT samples have been made with optimized structure parameters. Thirdly, using laser interferometry, voltage–displacement relationships of CPCT samples have been measured. Finally, the displacement hysteresis and the aging behavior of a CPCT have been analyzed.

The feasibility of synthetic aperture guided wave imaging to a mobile sensor platform

A mobile sensor platform that features a non-contact guided wave piezoelectric composite transducer payload for rapid inspection of large plate-like structures is presented. The paper begins with results from an experimental B-scan of an aluminium plate. Since the current guided wave payload uses 30mm square transducers (9λ wide) the system provides fairly course lateral resolution that in this case is approximately equal to the width of the transducer. The paper goes on to use simulation tools to examine the practical SNR and resolution limits of this approach. When using narrow aperture transducers that provide a wide field of view it is important to apply the synthetic aperture focusing technique to maximise image resolution. It is shown that resolution is a function of both transducer aperture and robot positional uncertainty since the effectiveness of synthetic aperture techniques is directly dependent on positional accuracy. It is also shown that since systems utilising larger aperture transducers with a narrow field of view are not as dependent on synthetic array reconstruction, they can outperform systems with narrower transducers in cases where there is relatively large positional uncertainty. Lastly the resolution and relative SNR are modelled as functions of transducer aperture for the cases of B-scan and synthetic array processing.

Electromechanical impedance of piezoelectric transducers for monitoring metallic and non-metallic structures: A review of wired, wireless and energy-harvesting methods

Electromechanical impedance–based structural health monitoring method had attracted several researchers in the recent past for aerospace, civil, mechanical, timber and biological structures. Smart materials such as piezoelectric (lead zirconate titanate) and macro fibre composite transducers are either surface bonded or embedded inside the host structure to be monitored. These smart materials with an applied input sinusoidal voltage interact with the structure, to sense, measure, process and detect any change in the selected variables (stress, damage) at critical locations. These can be categorized as wire-based ‘advanced non-destructive testing’, wireless-based ‘battery-powered lead zirconate titanate/macro fibre composite’ and energy harvesting–based ‘self-powered lead zirconate titanate/macro fibre composite’ methods. Most importantly, the effectiveness of these electromechanical impedance–methods can be classified into active and passive based on the properties of the material, the component and the structure to be monitored. Furthermore, they also depend on variables to be monitored and interaction mechanism due to surface bonding or embedment. This article presents some of the important developments in monitoring and the path forward in wired, wireless and energy harvesting methods related to electromechanical impedance–based structural health monitoring for metals and non-metals.

Coupled Vibration Analysis for a Composite Cylindrical Piezoelectric Ultrasonic Transducer

Coupled Vibration Analysis for a Composite Cylindrical Piezoelectric Ultrasonic Transducer

Analytical solution of piezoelectric composite stack transducers

This article presents the dynamic analytical solution of piezoelectric composite stack transducers under external harmonic mechanical loads, which is based on the linear theory of piezoelasticity. The solution is obtained by using the displacement method. The effects of the load frequency, the load amplitude, and the thickness of electrode on the dynamic characteristics of the transducers are discussed. Experimental results strongly verify the validity of the proposed theoretical analysis.

Piezoelectric fiber composite transducers for health monitoring in composite structures

This paper presents a critical study on the sensing characteristics of piezoelectric fiber composite transducers (PFCTs), in order to evaluate them as an effective embedded sensor inside the composite structures to monitor the stress/strain concentration levels at the critical locations. The functions of PFCT as an embedded sensor inside the composite structure are threefold: (i) to detect all loading conditions acting on to the structure, (ii) to predict the occurrence of damage while in-service under dynamic loads, and (iii) to monitor the pre-existing damages in the composite structures so that the severity can be ascertained to avoid eventual catastrophic or brittle failures. PFCT will be an ideal choice for composite structures applications, as they are highly flexible, easily embeddable; their high compatibility to the composite manufacturing techniques, and more importantly, it is expected that they will produce significantly less interfacial stresses when embedded inside the composite structures.Two types of PFCTs (macro fiber composite (MFC – from Smart Materials Corp.), and piezoelectric fiber composite (PFC – from Advance Cerametrics Inc.)) have been selected and calibrated by investigating their sensor performances based on characteristics; like transfer function, sensitivity, nonlinearity, resolution, and noise levels. Dynamic loads (transverse and longitudinal) have been applied and their corresponding output response is evaluated. The sensitivity of these products to the changes in frequencies and strain levels of input dynamic loads is investigated through the constant strain and frequency curves. Healthy voltage output response is observed even at low strain level domains, which indicates their high sensitivity and high resolution as a sensor. Comparing the results, it can be concluded that these sensors demonstrated their superior sensitivity and better performance over the traditional strain gauges. After a detailed sensor performance assessment, a case study has been conducted on the composite beam structure, where the ability of the PFCTs to detect the delamination of various levels inside the composite beam structure through modal analysis has been investigated. Then tests were performed to investigate the ability of the embedded PFCT sensors to detect the changes in the applied input mechanical stress/strain when embedded inside glass fiber–epoxy composite laminate samples. It is found that these sensors are effectively able to detect the changes in the applied input mechanical stress/strain. A linear relationship has been observed between the applied input mechanical stress and the sensor generated voltage output.

Design and Analysis of MEMS based Composite Piezoelectric Ultrasonic Transducer

With the rapid gro wth of technology, micro scale devices are p laying a do minant role in mechanical and optoelectronic devices. Characteristics like min iaturization, mult iplicity and microelectronics help these devices to sense, control and actuate on micro scale with effects on macro scale. M icro devices like co mposite transducers are widely used in med ical, industrial and space applications because they are relatively simple and easy to interface with other devices and also provide better resolution and easy installation. The present work reports the design and simulat ion of composite piezoelectric ultrasonic transducer, where susceptance was computed by applying AC potential for various piezoceramic materials i.e., Nepec 6, Quart z, Pzt-8. In this, an eigen frequency analysis is fo llo wed by a frequency response analysis to calculate the input admittance as a function of the excitation frequency. To make this design, COMSOL Mult iphysics software is used. The transducer designed with PZT-8 has exh ibited better sensitivity than others. These transducers are widely used in non-destructive testing (NDT), weld ing, machin ing, medical imag ing etc.

Ultrasound Flow Sensor Based on Arrays of Piezoelectric Transducers Integrated in a Composite

The functionalization of fiber-reinforced polymer composites by integration of piezoelectric transducers allows for both the measurement and the excitation of guided waves within the component. A common use for guided waves in composite components is nondestructive examination. In the presented work, however, the radiation of ultrasound waves from the surface of the component due to guided waves in the component is utilized. Glass fiber-reinforced polypropylene (GF/PP) plates with integrated arrays of piezoelectric macro fiber composite (MFC) transducers are used as ultrasound transmitter and receiver. The plates are then set up as facing walls of a rectangular duct and the sound transit times between the plates are measured. From the measured sound transit times, the velocity of gas flow inside the composite duct is determined. In that way, a flow sensor integrated in the walls of a flow channel, e.g. an air duct, made of composites is built. This paper focuses on the manufacturing of such an integrated flow sensor.