Focusing Ultrasonic Transducer Research Articles

Focused ultrasonic transducer for aircraft icing detection

Ultrasonic detection technique (UDT) serves as a pivotal method for monitoring aircraft icing conditions. However, the inherently porous and irregular shape of atmospheric ice leads to a pronounced attenuation of ultrasonic wave energy during propagation. Current ultrasonic transducers (UTs) fall short of meeting the requisite sensitivity and depth parameters for effective detection. This study proposes an innovative focused ultrasonic transducer (FUT) designed to extend the range of ice detection capabilities. Constructed using a 1–3 piezoelectric composite configuration, this FUT is characterized by its flexibility and slender profile. The focusing effect was accomplished through a deliberate bending mechanism. The FUT demonstrates its efficacy in detecting ice on aluminium skin surfaces. Furthermore, we validated the focusing effect and conducted a thorough optimization process. A comparative analysis between the FUT and traditional planar UTs revealed that the FUT enhances detection energy by approximately 30%, while also nearly doubling the detection range for glaze ice. These findings underscore the FUT’s promising potential for applications in the detection of substantial ice.

An ultrasonically catalyzed conductometric metal oxide gas sensor system with machine learning-based ambient temperature compensation

The ultrasonic catalysis method provides a new means of enhancing sensing performance of some types of gas sensors. But generating the ultrasound consumes electric energy and increases the system mass. Thus, it is significant to lower the energy consumption and mass of the ultrasonic excitation structure as much as possible, while enhancing the sensing performance. In this work, a thin conical metal shell excited by a piezoelectric disk has been proposed, serving as the focusing ultrasonic transducer and protection case for a SnO2 gas sensor. The ultrasonic transducer’s total mass is only 11 g. The experiments show that the ultrasonic transducer can significantly reduce the low detection limit (LDL), and measured LDL of the sonicated sensor for H2 can be as low as 107 ppb (1/3 of the same sensing element not sonicated) with a response of 4.6%. In this case, the ultrasonic transducer’s power consumption and temperature rise is 146 mW and 3 ℃, respectively. The low temperature rise indicates that the LDL may be further decreased by increasing the ultrasonic vibration. The effect of ambient temperature change on predicted H2 concentration is compensated by two convolutional neural networks for the low (1–100 ppm) and ultralow (≤ 1 ppm) concentration ranges, and the relative error of concentration prediction in these two concentration ranges is 5.7% and 12.3%, respectively.

대구경 선집속 초음파 탐촉자를 이용한 실리콘 판재의 결정방향 측정

대구경 선집속 초음파 탐촉자를 이용한 실리콘 판재의 결정방향 측정

지방 조직 유화를 위한 집속형 초음파 변환기 설계 및 제작에 관한 연구

초음파를 이용한 조직 자극 기법은 지속적으로 연구, 개발되고 있으며, 최근 미용 및 비만 치료에 대한 관심이 높아짐에 따라 초음파 지방 제거술에 대한 다양한 연구가 진행되고 있다. 본 연구에서는 초음파 지방 제거술을 위한 초음파 변환기를 설계하고, 조사조건에 따른 집속영역의 형태와 열 변성 영역을 시뮬레이션 하였다. 이를 통하여 제원을 검증하였으며, 제작된 변환기의 초음파 방사 특성 및 가열 특성을 측정하여 유효성을 평가하였다. 또한 복합 구조의 매질을 대상으로 초음파 가열 특성을 예측하였으며 제작된 변환기의 집속점 형태 및 가열 특성이 지방층을 충분히 유화시킬 수 있을 것으로 판단하였다. 본 연구의 결과는 보다 효율적이고 안전한 초음파 지방 제거술의 기초 연구로 활용될 것으로 사료된다.

Simulation and Experiment Researches on Acoustic Field of Spherical Shell Focused Ultrasonic Transducer

Aiming at the deficiency of existing focused ultrasonic technology, a new high-power Spherical Shell Focused Ultrasonic Transducer (SSFUT) was designed. The SSFUT is composed of a sandwich piezoelectric ultrasonic transducer and a bending vibration spherical shell. Simulation on acoustic field of SSFUT was carried out. the acoustic field pressure distribution nephogram and the axial acoustic pressure curve of the SSFUT were obtained. The consistency of finite element simulation results and experimental results was verified by testing. The research provides a theoretical basis for implementation and application of the new focused ultrasonic technology.

A Study of High Intensity Focusing Ultrasonic Transducer

High intensity focused ultrasound (HIFU) is the fourth brand-new and efficient means to cure tumour acknowledged by the medical field. Study of ultrasonic transducer is a core part of HIFU technique, In order to ensure reliability and safety of treatment, it is a key for HIFU technique to realize accurate focusing of ultrasonic energy. In the thesis, ultrasonic focusing method, studies of current situations of cell and multiplex array focusing transducers and their existing problems are illustrated based on analyzing challenges faced by HIFU treatment at present. This study suggested that phased array was theoretically easy for realizing accurate control of computer， however, unbeneficial factors and engineering technical problems still exist; How to promote intensity of the focal spot of cell array focusing transducer, enlarge scope of the focal area and improve control way of the focal spot was a bottleneck problem for publicizing and applying cell array focusing transducer and one of urgent research topics for ensuring curative effect of HIFU and avoiding heat damages.

PVDF 압전막을 이용한 초고주파 집속 초음파 트랜스듀서의 제작 및 특성 평가

높은 분해능의 영상을 얻는데 사용하기 위하여 초고주파 대역에서 동작하는 집속 초음파 트랜스듀서를 제작하고 그 특성을 평가하였다. 그 트랜스듀서는 한쪽 면에만 접지용 전극이 있는 두께 9 <TEX>${\mu}m$</TEX>의 PVDF 압전막의 다른 쪽 면에 CCP (Copper Clad Polyimide)막을 에폭시로 접착한 후, 금속구로 압착함에 의해 구각형을 형성시키고, 그 뒷면에 에폭시를 채워 몰딩 시키는 방법에 의해 만들어졌다. 제작된 곡률반경 7.5 mm, f-number 1.7의 트랜스듀서는 초점에 있는 표적에 대한 펄스에 코 측정결과 35.0 MHz의 대역폭을 가지며, 약 40 MHz인 피크주파수 부근에서의 삽입손실은 약 60 dB 을 나타내었는데, 그 측정결과는 에폭시 접착층의 두께를 고려한 KLM 등가회로 해석에 의한 시뮬레이션 결과와 유사한 것이었다. 나아가, 그 트랜스듀서에 의해 얻어진 가는 구리선 표적에 대한 영상을 35 MHz 트랜스듀서를 장착한 UBM (Ultrasonic Backscattering Microscope) 장치에 의한 영상과 비교한 결과, 측방향 분해능은 떨어지나 축방향 분해능은 다소 향상됨을 알 수 있었다. In order to obtain high resolution images, a focusing ultrasonic transducer operated in very high frequency (VHF) range was fabricated and its characteristics were evaluated. A 9-<TEX>${\mu}m$</TEX> thick PVDF film with only one metalized surface for electric ground was adhered to a CCP (Copper-clad polyimide) film by using epoxy. It was pressed by a metal ball to form a concave surface and its rear side was filled with the epoxy. The radius of curvature and the f-number of the fabricated transducer are 7.5 mm and 1.7, respectively. The pulse-echo measurement results from a target located at the focal point showed that the frequency bandwidth was 35.0 MHz and the insertion loss near the peak frequency of approximately 40 MHz was about 60 dB. Those values agreed well with the simulation results by the KLM equivalent circuit analysis including the effect of the epoxy bonding layer. When the image of thin copper lines by the 35 MHz transducer of the UBM (Ultrasonic Backscattering Microscope) system was compared with the image by the transducer fabricated in this study, the fabricated transducer was observed that the axial resolution was improved although the lateral resolution was degraded.

Evaluation of Rolling Fatigue Damage in Deep Groove Ball Bearings by Divided-Type Focusing Ultrasonic Transducer

To evaluate quantitatively the damage caused by rolling fatigue in deep groove ball bearings, we used a method in which the wave velocity of a leaky surface acoustic wave (SAW) propagating on the race surface of bearings was measured. The wave velocity was directly measured from the change in the propagation time by defocusing a focusing ultrasonic transducer. A new focusing ultrasonic transducer was developed by molding a piezoelectric copolymer into a concave-shaped film. To fabricate ultrasonic transducers with a lower frequency characteristic, the films were stacked and composite backings made from epoxy resin and tungsten were used. The electrode of the transducer was divided into three areas to receive direct reflection waves and leaky SAW independently without any interference. Two of these electrodes were used for the excitation and reception of leaky SAW, and the shape of the electrodes was designed so that leaky SAW might propagate only on the raceway surface of the inner ring of the bearings. Moreover, in order to suppress the effects caused by edge waves, the shape of the electrodes for leaky SAW was considered. The availability of this method was evaluated by measuring the leaky SAW velocity in the bearings whose worked hours differed. As a result, a small difference in leaky SAW velocity was detected according to the worked hours of the bearings, and it was demonstrated that this method would be useful for non-destructive soundness evaluation of bearings.

Ultrasonic enrichment of microspheres for ultrasensitive biomedical analysis in confocal laser-scanning fluorescence detection

An ultrasonic particle concentrator based on a standing-wave hemispherical resonator is combined with confocal laser-scanning fluorescence detection. The goal is to perform ultrasensitive biomedical analysis by concentration of biologically active microspheres. The standing-wave resonator consists of a 4 MHz focusing ultrasonic transducer combined with the optically transparent plastic bottom of a disposable 96-well microplate platform. The ultrasonic particle concentrator collects suspended microspheres into dense, single-layer aggregates at well-defined positions in the sample vessel of the microplate, and the fluorescence from the aggregates is detected by the confocal laser-scanning system. The biochemical properties of the system are investigated using a microsphere-based human thyroid stimulating hormone assay.

Characterization of an electrical melting point using a focusing transducer

The thickness resonances of an elastic plate normally insonified by an ultrasonic plane wave are well known. From these resonance frequencies, the plate thickness can be easily deduced. In this paper, we use a focusing ultrasonic transducer with a large bandpass to characterize an electrical melting point between two steel plane shells. This solder type is abundantly used in the manufacturing of cars. The solder is placed in the focal spot of the beam. The transducer can be parallely moved to the surface of the sheet steel. A number of time signals are recorded along a diametrical line of the melting point with a small step. For each time signal, two spectra are computed: the magnitude spectrum also called backscattered spectrum and the phase spectrum. The results are processed with graphic software. The different images allow the evaluation of the quality of an electrical melting point.

Measuring scanning acoustic microscope with a harmonic sounding signal

A concept of a scanning acoustic microscope with a harmonic sounding signal for measuring the parameters of local homogeneous regions of flat samples is proposed. The distinctive feature of the device is the utilization of the Doppler effect that occurs in the sounding wave reflected from the sample surface when the sample is uniformly moved relative to the focusing ultrasonic transducer of the microscope. It is theoretically demonstrated that the spectrum of the received signal is determined by the product of the reflection coefficient and the transfer function of the transducer. The errors of the measurement technique are considered, and the sources of signal distortions are analyzed. High sensitivity of the measurement results to the errors of the scanning system is demonstrated. The developed measuring microscope is described, in which an acoustic interferometer is used to provide the necessary precision of the scanning coordinate measurement. The microscope transfer function is measured for the frequency of the sounding signal 65 MHz, and the values of density and bulk wave velocities are determined for a homogeneous sample by the measured phase of the reflection coefficient using the technique of nonlinear estimation of parameters. With fused quartz used as an example, it is shown that the measurement error is 7.2% for density and 2.3 and 0.7% for the velocities of longitudinal and transverse waves, respectively. In addition, the velocity of a leaky surface wave (SAW) is determined by two methods. One method is based on measuring the position of the inflexion point for the experimental phase of the reflection coefficient, and the other is based on calculating the SAW velocity corresponding to the measured values of density and bulk wave velocities. The errors of these methods are found to be equal to 0.42 and 0.17%, respectively.

The multicomponent composition of the low acoustic impedance matching layer for the ultrasonic transducer operating in the air

Piezoceramic transducers with matching layers are usually used to generate an ultrasonic wave in the air within the frequency range above 100 kHz. The paper presents a new material composition of low acoustic impedance named ITAKOM, whose acoustic characteristics makes it applicable as a matching medium between a piezoelectric transducer and a gas medium in a wide range of frequencies. Porosity is the common feature of all the lowest acoustic impedance materials. The results of the studies of different material compositions show that pore diameters and their percentage in the composite volume have greater importance than the composite make-up and render possible the elaboration of a composite material whose parameters can be defined by the percentage interdependence of components. Due to the comparatively wide range of density and wave velocity materials of acoustic impedance ranging from 0.2 −1×106 Pa⋅s/m can be produced. An example of an application of this material to construct the focusing ultrasonic transducer operating in the air at the frequency f=1.3 MHz in the setup of phase sensitive scanning acoustic microscopy as well as the results of object measurements are presented in the ultrasonic journal [Gudra et al., Ultrasonics 34, 711–719 (1996)].

Determination of the group and phase velocity surfaces of acoustic waves in anisotropic materials by ultrasonic acoustic microscopy with phase contrast

A new method to determine the group and phase velocity surfaces using only one image in phase contrast detected by phase sensitive scanning acoustic microscopy (PSAM) has been developed. Similar to earlier techniques, a focusing ultrasonic transducer is adjusted to a spot on a surface of a sample. A second similar transducer is scanned with the focus in the plane of the opposing planar surface. In the application presented here the group and phase velocity surfaces are derived from the observed phases of the transmitted ultrasonic waves. Numerical methods have been developed to achieve a continuous representation of the phases from the measured images. Subsequently the data is corrected for geometrical effects caused by the planar scanning sheet leading to a three-dimensional representation of the velocity surfaces. By additional procedures based on simple geometrical conditions, the phase velocities are derived in a straightforward way from the group velocities.

A new focusing ultrasonic transducer and two foci acoustic lens for acoustic microscopy

The textured piezoelectric film of a new organic-based material produced by vapor deposition was used as an active element of a focusing ultrasonic transducer. The transducer exhibits near theoretical lateral and axial resolution, unipolar pulse response to a step voltage, and 30 dB insertion losses in an octave frequency band. The transducer is acoustically transparent over a wide frequency range and can be fabricated on a concave spherical surface of the standard acoustic lens. The resulting double transducer and two foci acoustic lens are capable of improving the quality of the surface structure imaging or of being used in continuous wave reflection acoustic microscopy.

Use of focused ultrasonic receivers for remote measurements in biological tissues.

The feasibility of using a focusing ultrasonic transducer as a sound pressure receiver is discussed. It is shown theoretically that, at certain angular apertures of the receiver, its output signal is proportional to the sound pressure in the field point coincident with the receiver center of curvature. The receivers of this type have been demonstrated suitable for remote measurements of field spatial distribution of plane and focused ultrasonic radiators. Data are presented on the experimental testing of focused receivers in measuring acoustic fields in water, air, and certain samples of biological tissues. The instruments are sufficiently universal and allow the measurement not only of acoustic fields, but also of temperature increments in locally heated media, as well as permit one to follow the initiation and development of ultrasonic cavitation and study nonlinear effects. The remote sensing ability and high sensitivity of focused ultrasonic receivers allow their practical use in biomedical acoustics for noninvasive measurements.

Characteristics of the focusing ultrasonic transducer with wideband frequency.

Characteristics of the focusing ultrasonic transducer with wideband frequency.