Design Of Ultrasonic Transducers Research Articles

Variable-thickness multilayered polyvinylidene fluoride transducer with improved sensitivity and bandwidth for photoacoustic imaging

The performance of photoacoustic imaging (PAI) is critically dependent on the sensitivity and bandwidth of the transducer. Here, we report the design and fabrication of a polyvinylidene fluoride ultrasonic transducer with variable-thickness layers that demonstrates significantly improved sensitivity and bandwidth. We show that the multilayered transducer provides more than 2-fold increase in sensitivity and more than 65% improvement in bandwidth compared with the conventional single-layer transducer. Photoacoustic imaging of mouse brain with the intact skull and scalp is conducted to demonstrate the power of the multilayered transducer for resolving brain structure in an in vivo setting.

Optimal Design of an Ultrasonic Transducer in Rotary Ultrasonic Machining

In this paper, an ultrasonic transducer is designed and optimized in order to reduce the error of resonance frequency and maximize the amplitude of the radiating tip. In order to get the basic dimensions of an ultrasonic transducer easily, resonance frequency equations are derived by using the traditional analytic method. Using ANSYS FEM software, we analyzed the vibration model of the transducer, including Modal Analysis and Harmonic Response Analysis. Studied how the length of two resonance rods affects the resonance frequency. By optimizing the dimensions of the ultrasonic transducer, the error of resonance frequency is reduced to 0.03%; the amplitude of the vibrating tip is up to 6.20μm. The optimal results show that the transducer designed in this paper has superior performance parameters and meets the requirements of machining.

Design and fabrication of nanoscale ultrasonic transducers

The development of nanometre sized ultrasonic transducers is important in both biological and industrial applications. The small size can be important in its own right or necessary in order to generate acoustic waves with nanometric wavelengths. Potential applications of nanotransducers range from embedded sensors through to sub optical wavelength acoustic imaging. In this paper we discuss the design and fabrication of nanoscale ultrasonic transducers. The transducers rely on optical and mechanical resonances, they can be used to generate and detect high frequency ultrasound in a sample. The mechanical and optical performance of the devices have been extensively modelled using both analytical techniques and finite element modelling. This allows the fine tuning of the design parameters to ensure optimised performance for the experimental configuration. The devices can be fabricated in a number of ways, we present one method for building these types of devices, a 'top down' approach where plate structures are built up and patterned using standard photolithographic techniques. This method produces nanoscale devices in one dimension only (the others being a few microns) but produces excellent devices for testing in situ and for comparison to the models as they are easy to handle and measure. Approaches for reducing the other dimensions to the nanoscale will also be considered.

Detailed investigation of capacitive micromachined ultrasonic transducer design space

In this study, we present general design guidelines for MEMS ultrasonic transducers, capacitive micromachined ultrasonic transducers (CMUTs), obtained from finite element models with a statistical design of experiment approach. The design space is illustrated using 2-D response surfaces as a function of various geometrical parameters and material selections. Important transducer figure of merits such as operation frequency, fractional bandwidth, collapse voltage and transformer ratio are investigated. Our study illustrates that while keeping geometrical parameters constant, changing the material selection to silicon carbide from silicon dioxide results in a 2.4 times increase in the transformer ratio, and more than 2.5 times increase in the operating frequency while keeping the bandwidth the same. Furthermore, our studies indicate that for a CMUT membrane with an aspect ratio of 4, using a spring constant value obtained analytically results in an error of 160% for the collapse voltage and transformer ratio values.

Characterization and Modelling of Circular Piezoelectric Micro Speakers for Audio Acoustic Actuation

A study of circular piezoelectric micro speakers is presented for applications in the audio frequency range, including values for impedance, admittance, noise figures, transducer gain, and acoustic frequency responses. The micro speakers were modelled based on piezoelectric micro ultrasonic transducer (pMUT) design techniques and principles. In order to reach the audio frequency range, transducer radii were increased to the order of one centimetre, whilst piezoelectric layer thicknesses ranged the order of several μm. The micro actuators presented might be used for a variety of electroacoustic applications including noise control, hearing aids, earphones, sonar, and medical diagnostic ultrasound. This work main contribution is the characterization of the design space and transducer performance as a function of transducer radius, piezoelectric layer thickness, and frequency range, looking towards an optimized fabrication process.

Effect of Inter-Rod Coupling on 1-3 Piezocomposite High-Power Ultrasonic Transducers

Efficiency is a critical performance for a high-power ultrasonic transducer composed of 1-3 piezocomposites and geometric parameters of the composites can influence the efficiency of the transducer. The effect of inter-rod responses in the composite matrix on the efficiency was experimentally investigated in this study. For analyses, four PZT4-epoxy composite ultrasonic transducers with various volume fractions and inter-rod spacing were fabricated in-house. The experimental results demonstrated that the inter-rod coupling of the 0.1-mm spacing could significantly degrade the efficiency of the composite probe at about 1.0 MHz resonance since the 0.1-mm spacing between PZT4 rods was so small as to cause a high interference. At the same volume fraction, the transducer engineer should take the inter-rod coupling into account for the design of the high-power ultrasonic transducer.

Metal rings and discs Matlab/Simulink 3D model for ultrasonic sandwich transducer design

Metal-endings are integral part of different ultrasonic sandwich transducers. In this paper a new Matlab/Simulink 3D model of the finite metal rings and discs of various dimensions is realized. With this model, which describes both the thickness and the radial resonant modes, and the coupling between them, mechanical impedance of the sample can be easily computed. Resonance frequency-length curves for rings and disks with various materials and for different selected dimensions are given. Also, comparisons of the different approaches in determining of their resonant frequencies are shown. The proposed Matlab/Simulink model requires simpler implementation than other analytical models. That enabled modifying of 1D theory and simplified modelling and projecting of the ultrasonic sandwich transducers with short-endings. Finally, the computed and experimental results are compared.

Driver Design of the Piezoelectric Ultrasonic Transducer for Wire Bonding Based on Direct Digital Synthesis Technology

In order to design a driver of piezoelectric ultrasonic transducer which can provide high quality ultrasonic signal and be able to realize the frequency tracking rapidly, accurately and intelligently during the bonding process, the ATmega128 microcontroller and AD9851 synthesizer are selected as core components to build an ultrasonic generator and frequency tracking system. The basic circuit units including low pass filter, power amplifier, signal detection and conversion circuits are also established. The test results of the system shows that, based on DDS technology, high quality ultrasonic signal for transducer can be achieved. By combining the two kinds of frequency tracking methods, the system can realize the frequency tracking during the bonding process. It also indicates that the design significantly improve the precision and flexibility of the ultrasonic generator system.

Airborne ultrasonic vortex generation using flexible ferroelectrets

Cellular ferroelectrets exhibit interesting electromechanical- acoustical characteristics. Their recent appearance and remarkable properties open up new possibilities for the design and development of ultrasonic transducers. In particular, the feasibility of fabricating ultrasonic vortex generators using ferroelectret films is demonstrated in this work. To this end, a transducer prototype was built by gluing the material onto a tangential-helical surface (outer diameter: 40 mm, pitch: 3.45 mm). Experimental results agree well with the theoretical estimation of the pressure and phase of the acoustic field in the near field and far field, which corroborates the potential of ferroelectrets to customize special acoustic fields. Furthermore, the proposed fabrication procedure is inexpensive and represents a new alternative for exploring and analyzing the special characteristics of acoustical helical wavefronts.

Structural health monitoring using polymer-based capacitive micromachined ultrasonic transducers (CMUTs)

Transducers based on a capacitive micromachined ultrasonic transducer (CMUT) design have been fabricated using a rapid prototyping technique. This results in a device that is constructed principally from polymers, in a process which is simple and inexpensive. The resultant devices can be attached to the surfaces of solids. Their peak sensitivity is in the 80–100 kHz range, making them ideal for applications such as acoustic emission and structural health monitoring. Good low frequency sensitivity leads to applications in vibration monitoring.

Multi-Objective Optimization of a Piezoelectric Sandwich Ultrasonic Transducer by Using Elitist Non-Dominated Sorting Genetic Algorithm

The multi-objective optimal design of a piezoelectric sandwich ultrasonic transducer is studied. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (material types). Based on analytical models, the optimal design is formulated as a constrained multi-objective optimization problem. The optimization problem is then solved by using the elitist non-dominated sorting genetic algorithm (NSGA-II) and Pareto-optimal designs are obtained. The optimized results are analyzed and the preferred design is proposed. The optimization procedure presented in this contribution can be applied in multi-objective optimization problems of other piezoelectric transducers.

Modulation of the bandgaps of in-plane elastic waves by out-of-plane wavenumber in thepiezoelectric composite structures

We study theoretically the modulation of bandgaps of in-plane elastic waves by theout-of-plane wavenumber that is parallel to the piezoelectric material rod axis inpiezoelectric composite structures. The dependence of bandgaps of in-plane elasticwaves on the out-of-plane wavenumber and the filling fraction are calculatedwith and without the composite’s piezoelectricity. The in-plane bandgaps can beopened (or closed) and the in-plane wave modes can be tuned by controlling thepropagation of out-of-plane elastic waves. The in-plane bandgap in the low-frequencyrange can be easily obtained by introducing an out-of-plane wavenumber, and isalmost independent of the composite’s piezoelectricity. Meanwhile, the widths andstarting frequencies of in-plane bandgaps in a relatively high-frequency range canbe modulated by the filling fraction and the composite’s piezoelectricity. Thepiezoelectric composite structure is very useful in the design of ultrasonic transducers toavoid the invalid modes of in-plane elastic waves without affecting the workingmodes corresponding to the out-of-plane wavenumber. The method to calculatethe total transmission spectrum of elastic waves in this paper is useful to studypiezoelectric composite structures with finite length in engineering applications.

A Model for Ultrasonic Testing Conical Transducer and Optimal Design

In this paper, a numerical modeling of contact conical transducers is discussed in conjunction with wave propagation analyses by a finite difference method (FDM). Although transducers are the devices to convert electrical energy into mechanical energy and vice versa, attention in this paper is paid mostly to the study of characteristics and parameters of cones and wedges influencing their performance. Cones and wedges inserted between an ultrasonic transducer and the specimen provide the transducer with enhanced capability for point or line contact with the specimen. We study the effect of the dimensions, shape and aperture on the frequency response and the angle of incidence of the wave. Through the testing transducer modeling, some conclusions have been drawn from the analysis, which is useful to as the guideline and criteria for an optimum conical wedge design.

Design and fabrication of ultrasonic transducers with nanoscale dimensions

The development of nanometre sized ultrasonic transducers is important in both biological and industrial applications. The small size can be important in its own right or necessary in order to generate acoustic waves with nanometric wavelengths. Potential applications of nanotransducers range from embedded sensors through to sub optical wavelength acoustic imaging. In this paper, we show the generation and detection of ultra high frequency acoustic waves using nanometre scaled optical ultrasonic transducers. The optical and mechanical properties of these devices have been modelled using finite element modelling (FEM) and analytical techniques. The models allow the fine tuning of the design parameters to enhance both the acoustic and optical performance of the transducers. The devices were fabricated by evaporating the required metal and transparent layers onto a substrate, and then surface patterning of the device was created by laser machining or photolithography, thus allowing close comparison between model and experiment. We discuss the transducer design process and the effect of the coating parameters and how these affect the operating frequency and efficiency of the devices. We discuss the possibility of using molecular self assembly to produce even smaller devices.

Modelling and optimum design of ultrasonic transducer for therapy application

In ultrasound imaging applications, transducers with high sensitivity, good impulse response, low-ripple, and wide-band performance are desired. Widening the bandwidth of transducers by introducing quarter-wavelength matching layers on the piezoelectric ceramic may result in a reduction in power transmission and sensitivity. For therapy, it is more important to have high-transmitting power than to have wide-bandwidth characteristics. Since a 15% bandwidth is sufficient for therapy applications, a matching-layer thickness that is a little bit shorter or longer than one-quarter wavelength is proposed as a good trade-off between the two criteria. By tuning the thickness and acoustical impedance of the matching layer, transducers with optimum bandwidth and transmitting power can be obtained. An acoustical lossy transmission line model for an ultrasonic transducer is proposed. Then, the developed model is implemented on PSPICE-controlled source programming technology to precisely predict the performance of the transducer's characteristics. Good agreement between the simulation results and experimental results has been achieved.

Design and development of a multi-hole broadband-based ultrasonic transducer

In order to improve the efficiency of ultrasonic energy transformed from electricity for an ultrasonic transducer array, a novel 1/2 wavelength multi-hole broadband-based transducer was designed, developed and evaluated. The low equivalent mass of the transducer is realized in this work through drilling holes on the output end of the horn. In comparison with a traditional transducer, the developed transducer has demonstrated a lower mechanical quality coefficient and a wider broadband. As a result, an ultrasound treatment system for crude oil has been developed based on the new transducer design. Furthermore, we have demonstrated the effectiveness of the ultrasound treatment system on viscosity reduction of crude oil and paraffin.

Ultrasonic Transducer Design via APDL Optimization

The design of ultrasonic transducer is used to achieve the desired value of terminal vibration amplitude. However, in many practical applications of ultrasonic transducer, the maximum vibration amplitude failed to achieve that value such as ultrasonic machine and bonding. For that matter, the design of ultrasonic transducer used APDL optimization method. In this paper the optimal design of a sandwich ultrasonic transducer is investigated. The design problem is formulated mathematically as a constrained single-objective optimization problem. The maximum vibration amplitude is considered as optimization objective. Design variables involve continuous variables and discrete variables. What is more, the behavior of ultrasonic transducer is modeled using ANSYS based on models of the transfer matrix method. In this paper, the optimized results are analyzed and the vibration amplitude is determined.

Building of Ultrasonic Vibration Precision Cutting System and Experimental Study of Cutting for Plastic Material

Precision ultrasonic vibration cutting (UVC) is a promising technology in field of precision and ultra-precision machining. It is a kind of the pulsing cutting process with a constant vibration frequency and sine-wave amplitude of vibration. Its practicability has been a research focus since it came into being. In this article, an precision UVC system is built by designing this system, including the selection of precision machine and ultrasonic generator, the design of ultrasonic transducer, and then many cutting experiment are been done. Different of chips under the conditions of ultrasonic and no ultrasonic are made, and deformation coefficient of chip obtained by vibration cutting is smaller. The effect of cutting parameters on roughness is discussed in precision vibration cutting, the surface roughness decreased with the increase of the amplitude and the decrease of the cutting depth or feed rate, at the same time, there is an optimum cutting speed to receive the best surface.

Properties study of LiNbO3 lateral field excited device working on thickness extension mode

This paper investigates the properties of thickness extension mode excited by lateral electric field on LiNbO3 by using the extended Christoffel–Bechmann method. It finds that the lateral field excitation coupling factor for a-mode (quasi-extensional mode) reaches its maximum value of 28% on X-cut LiNbO3. The characteristics of a lateral field excitation device made of X-cut LiNbO3 have been investigated and the lateral field excitation device is used for the design of a high frequency ultrasonic transducer. The time and frequency domain pulse/echo response of the LiNbO3 lateral field excitation ultrasonic transducer is analysed with the modified Krimholtz–Leedom–Matthae model and tested using traditional pulse/echo method. A LiNbO3 lateral field excitation ultrasonic transducer with the centre frequency of 33.44 MHz and the −6 dB bandwidth of 33.8% is acquired, which is in good agreement with the results of the Krimholtz–Leedom–Matthae model. Further analysis suggests that the LiNbO3 lateral field excitation device has great potential in the design of broadband high frequency ultrasonic transducers.

Equivalent Circuit Analysis and Design of Multilayered Polyurea Ultrasonic Transducers

In this paper, we carried out equivalent circuit analysis for a multilayered transducer including the backing and load effects. The calculated resonance frequencies showed good agreement with previously measured values. The improved multilayered transducers in this study exhibit good characteristics for output sound pressure when loaded with water. We also demonstrated designs for a four-layer polyurea transducer with a frequency of up to 220 MHz. As a result, designs for a wide frequency range can be obtained by varying the polyurea thickness.