Design and Fabrication of Air-Based 1-3 Piezoelectric Composite Transducer for Air-Coupled Ultrasonic Applications (original) (raw)
Related papers
Ultrasonics, 2017
This paper details the development of a novel method for increasing the operational bandwidth of piezocomposites without the need for lossy backing material, the aim being to increase fractional bandwith by geometrical design. Removing the need for lossy backing materials, should in turn increase the transmit efficiency in the desired direction of propagation. Finite element analysis has been employed to determine the mode of operation of the new piezocomposite devices and shows good correlation with that derived experimentally. Through a series of practical and analytical methods it has been shown that additional thickness mode resonances can be introduced into the structure by a simple machining process. The shaped composites described in this paper offer increased operational bandwidth. A simple example of a two step thickness design is described to validate and illustrate the principle. A more complex conical design is presented that illustrates a possible tenfold increase in bandwidth from 30kHz to 300kHz, operating in air without backing. An illustration of the applicability of this type of transducer technology for frequency agile guided mode non-destructive evaluation is then presented.
2018
Common air-coupled transducers for non-destructive testing consist of a piezocomposite material and several matching layers. Better acoustical matching to air is achieved by transducers based on charged cellular polypropylene (PP). This material has about hundred times lower acoustic impedance than any piezocomposite, having about the same piezoelectric coefficient. The piezoelectric properties of cellular PP are caused by the polarization of air cells. Alternatively, a ferroelectret receiver can be understood as a capacitive microphone with internal polarization creating permanent internal voltage. The sensitivity of the receiver can be increased by applying additional bias voltage. We present an ultrasonic receiver based on cellular PP including a high-voltage module providing bias voltage up to 2 kV. The application of bias voltage increased the signal by 12 to 15 dB with only 1 dB increase of the noise. This receiver was combined with a cellular PP transmitter in through transmi...
A 3D model of new composite ultrasonic transducer
Journal of Computational Electronics, 2017
A three-dimensional (3D) model of a high-power ultrasonic, composite, unidirectional transducer is proposed in this paper. The proposed 3D Matlab/Simulink model of the composite transducers predicts the thickness and the radial modes of oscillation as well as their mutual couplings. This longitudinal, prestressed, asymmetrical, piezoelectric transducer, which consists of two active piezoelectric layers, front, back and central oscillating metal mass, is realized. Due to its special structure, the central mass is not bounded using a bolt and performs unidirectional piston motion as compression and expansion occur in cycles keeping the axial dimension of the transducer roughly constant because of mutually opposite polarization of active elements. The electromechanical equivalent circuit of the transducer, representing one-dimensional (1D) model, is derived first and is also presented in this paper, while the resonance frequency equation is obtained analytically. Few composite transducers are designed and manufactured. Their resonance frequencies are measured and compared with the analytically obtained results for a large number of electrical connection combinations. In order to demonstrate the capabilities and limitations of the 1D model, comparison with the results from the 3D model are made. Results show that the measured frequencies are in good correspondence with the analytically obtained from 1D model only for the thickness modes and from the 3D model for the thickness and the radial modes of oscillation and their mutual coupling.
Comparative Study of Different Piezo-Electric Materials Based Ultrasonic Transducer Model
In recent years, MEMS (micro-electrical mechanical systems) microphones have been used as low-cost alternatives to more costly phased arrays condenser microphones. More study of MEMS has shown significant importance for miniaturized mechanical system, based on silicon technology. Prior to fabrication of MEMS device design and simulation are extensively need to avoid expensive time and cost. The goal of the present work is to described the design of piezo electric transducer; particularly ultrasonic microphone. This microphone device is generally useful for generation of sound either in air or in water. COMSOL Multiphysics 4.1 is versatile software is used to solve the microphone device with 3D partial differential equations. In this paper, 2D axis-symmetry model geometry of phase arrays microphone was designed with lead zirconate titanate (Pb [Zr x Ti 1-x ] O 3) and barium sodium niobate (Ba 2 NaNb 5 O 15) piezo-electric materials. To investigate with the lead contact PZT with respect to lead free BNN materials has been carried out. The surface and radial displacement of the microphone structure of both the materials with pressure are studied.
2016 IEEE International Ultrasonics Symposium (IUS), 2016
The potential of additive manufacturing (AM) to revolutionize aspects of industrial production is widely recognized. AM can create objects with non-uniform properties by varying the ratio between deposited materials or altering the internal structure of the object. Amongst many possibilities, such AM objects could benefit the design and fabrication of different passive components of ultrasonic transducers, e.g. backing material, lenses and matching layers. The acoustic properties of AM objects produced using the Polyjet and Fused Deposition Methods were characterized. Initial results suggest that these technologies can easily produce objects with a wide range of tuned acoustic properties by varying either the internal structure or the material composition.
Air-Coupled Low Frequency Ultrasonic Transducers and Arrays with PMN-32%PT Piezoelectric Crystals
Sensors, 2017
Air-coupled ultrasonic techniques are being increasingly used for material characterization, non-destructive evaluation of composite materials using guided waves as well as for distance measurements. Application of those techniques is mainly limited by the big losses of ultrasonic signals due to attenuation and mismatch of the acoustic impedances of ultrasonic transducers and air. One of the ways to solve this problem is by application of novel more efficient piezoelectric materials like lead magnesium niobate-lead titanate (PMN-PT) type crystals. The objective of this research was the development and investigation of low frequency (<50 kHz) wide band air-coupled ultrasonic transducers and arrays with an improved performance using PMN-32%PT crystals. Results of finite element modelling and experimental investigations of the developed transducers and arrays are presented. For improvement of the performance strip-like matching elements made of low acoustic impedance, materials such as polystyrene foams were applied. It allowed to achieve transduction losses for one single element transducer −11.4 dB, what is better than of commercially available air-coupled ultrasonic transducers. Theoretical and experimental investigations of the acoustic fields radiated by the eight element ultrasonic array demonstrated not only a good performance of the array in a pulse mode, but also very good possibilities to electronically focus and steer the ultrasonic beam in space.
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2013
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(Mg 1/3 Nb 2/3)O 3-xPbTiO 3 (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. Changgeng Liu obtained his Ph.d. degree in engineering from Tsinghua University, beijing, china, in 2001, and his b.s. and m.s. degrees in aircraft design and mechanics from nanjing University of aeronautics and astronautics, nanjing, china. He is currently a senior scientist at Geospace research Inc., El segundo, ca, and a visiting scholar at the nIH resource center on medical Ultrasonic Transducer Technology of the University of southern california, los angeles, ca. Prior to joining Geospace research Inc. in 2007, dr. liu held a position as a research associate at the center for advanced microstructures and devices (camd) of louisiana state University, baton rouge, la. dr. liu is a senior member of IEEE. He has published more than 50 journal papers. dr. liu's research interests include high-frequency ultrasonic transducers and arrays, piezoelectric composite materials, mEms/ biomEms, and micromachined biomedical devices.
Design considerations for 1-3 composites used in transducers for medical ultrasonic imaging
Ceramic polymer piezoelectric composites with 1-3 connectivity have become an important tool in the design and manufacture of thickness mode transducers for medical diagnostic ultrasonic imaging. The major reasons for this are that, relative to piezoelectric ceramics alone, the composite can be designed with higher thickness coupling coefficient. acoustic impedance can be more closely matched to human tissue, arid low frequency lateral resonances can be suppressed. These improvements can lead to higher sensitivity and bandwidth in the transducer and reduce ringing due to unwanted modes of vibration. This paper compares annular array transducers made from ceramics alone to those made with composites to demonstrate the advantages of composites, and examines some of the trade-offs involved in optimizing composite designs for this application. Effects of varying Young's modulus and Poisson's ratio of the polymer phase on coupling coefficient and high frequency lateral resonances of the composite are presented.
Low-impedance and low-loss customized materials for air-coupled piezoelectric transducers
2001
For efficient operation of air-coupled piezoelectric transducers (frequency >0.5 MHz) new materials to produce quarter-wavelength matching layers are required. Low acoustic impedance, low attenuation coefficients and the possibility to produce thin membranes attachable to the transducer surface are the main requirements. Two candidate-materials were selected, manufactured and characterized: SiO 2 aerogel and highly porous PMMA. From the obtained results the suitability of such materials for this particular application is discussed and compared with other materials currently in use
UNIDIMENSIONAL MODELING AND CONSTRUCTION OF A 1-3 PIEZOELECTRIC COMPOSITE TRANSDUCER
2000
In many applications, such as medical imaging and nondestructive testing, broadband ultrasonic transducers capable of producing short pulses are required. Combining a piezoelectric element and a passive polymer to form a piezoelectric composite allows the development of transducers with high bandwidth and sensitivity, and low radial coupling. This work presents the modeling and construction of an ultrasonic transducer using a 1-3 piezoelectric composite. A simple physical model is used to calculate the effective properties of the composite. This model can be applied when the lateral spatial scale of the composite is sufficiently small so that the composite can be treated as an effective homogeneous medium. The effective properties are used in a distributed matrix model to calculate the electrical impedance of the composite. It is used the dice-and-fill technique to construct a 1-3 lead zirconate titanate(PZT)/epoxy 800 kHz, 20 mm diameter composite. The simulated results of the electrical impedance are compared with the experimental results measured by an impedance analyzer equipment. Finally, the ultrasonic transducer is constructed using the piezoelectric composite. The impulse response of the transducer is measured and compared with the theoretically obtained using the distributed matrix model. The experimental results show excellent agreement with the simulated ones. , Ouro Preto, MG