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Keywords = sandwiched piezoelectric ultrasonic transducers

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13 pages, 14364 KiB  
Article
Bimorph Dual-Electrode ScAlN PMUT with Two Terminal Connections
by Meilin Ji, Haolin Yang, Yongxin Zhou, Xueying Xiu, Haochen Lv and Songsong Zhang
Micromachines 2022, 13(12), 2260; https://doi.org/10.3390/mi13122260 - 19 Dec 2022
Cited by 13 | Viewed by 3852
Abstract
This paper presents a novel bimorph Piezoelectric Micromachined Ultrasonic Transducer (PMUT) fabricated with 8-inch standard CMOS-compatible processes. The bimorph structure consists of two layers of 20% scandium-doped aluminum nitride (Sc0.2Al0.8N) thin films, which are sandwiched among three molybdenum (Mo) [...] Read more.
This paper presents a novel bimorph Piezoelectric Micromachined Ultrasonic Transducer (PMUT) fabricated with 8-inch standard CMOS-compatible processes. The bimorph structure consists of two layers of 20% scandium-doped aluminum nitride (Sc0.2Al0.8N) thin films, which are sandwiched among three molybdenum (Mo) layers. All three Mo layers are segmented to form the outer ring and inner plate electrodes. Both top and bottom electrodes on the outer ring are electrically linked to the center inner plate electrodes. Likewise, the top and bottom center plate electrodes are electrically connected to the outer ring in the same fashion. This electrical configuration maximizes the effective area of the given PMUT design and improves efficiency during the electromechanical coupling process. In addition, the proposed bimorph structure further simplifies the device’s electrical layout with only two-terminal connections as reported in many conventional unimorph PMUTs. The mechanical and acoustic measurements are conducted to verify the device’s performance improvement. The dynamic mechanical displacement and acoustic output under a low driving voltage (1 Vpp) are more than twice that reported from conventional unimorph devices with a similar resonant frequency. Moreover, the pulse-echo experiments indicate an improved receiving voltage of 10 mV in comparison with the unimorph counterpart (4.8 mV). The validation of device advancement in the electromechanical coupling effect by using highly doped ScAlN thin film, the realization of the proposed bimorph PMUT on an 8-inch wafer paves the path to production of next generation, high-performance piezoelectric MEMS. Full article
(This article belongs to the Special Issue Design, Fabrication, Testing of MEMS/NEMS)
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16 pages, 4107 KiB  
Article
Research on Inherent Frequency and Vibration Characteristics of Sandwich Piezoelectric Ceramic Transducer
by Yuren Lu, Chunguang Xu, Qinxue Pan, Quanpeng Yu and Dingguo Xiao
Sensors 2022, 22(23), 9431; https://doi.org/10.3390/s22239431 - 2 Dec 2022
Cited by 1 | Viewed by 3218
Abstract
Great progress has been made in the field of ultrasonic processing in recent years, and piezoelectric ceramic transducers have been widely used as drive sources. In this paper, a sandwich piezoelectric ceramic transducer is designed, and the vibration of each part of the [...] Read more.
Great progress has been made in the field of ultrasonic processing in recent years, and piezoelectric ceramic transducers have been widely used as drive sources. In this paper, a sandwich piezoelectric ceramic transducer is designed, and the vibration of each part of the transducer is analyzed by elastic mechanics and piezoelectric theory. According to its mechanical and electrical boundary conditions, the vibration model of the piezoelectric transducer was established. Based on the equivalent elastic modulus method for simplifying the pre-stressed bolts into a one-dimensional transducer vibration model, the relationship between the one-dimensional axial response frequency of the transducer and the length of each component was obtained. Based on the half wavelength theory, a transducer with the vibration node in the crystal stack and an inherent frequency of 15 kHz was designed and fabricated. In order to verify the natural frequency and vibration characteristics of the piezoelectric transducer, a laser vibration measurement system was built in this study. The vibration characteristics of the transducer under different parameters such as voltage and frequency were analyzed, and the accuracy of the vibration model was verified. The vibration states of the end surface of the transducer and the radial surface were evaluated at the first-order inherent frequency and second-order inherent frequency. The results show that the equivalent simplified model established in this study can effectively design the inherent frequency of the transducer, and the operation at the first-order inherent frequency meets the one-dimensional assumptions of this study. The transducer operating conditions measured in this study also provide a more detailed reference for ultrasonic processing applications. Full article
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21 pages, 10738 KiB  
Article
Enhancement of the Transmission Performance of Piezoelectric Micromachined Ultrasound Transducers by Vibration Mode Optimization
by Penglu Li, Zheng Fan, Xiaoya Duan, Danfeng Cui, Junbin Zang, Zengxing Zhang and Chenyang Xue
Micromachines 2022, 13(4), 596; https://doi.org/10.3390/mi13040596 - 10 Apr 2022
Cited by 8 | Viewed by 3651
Abstract
Ultrasound is widely used in industry and the agricultural, biomedical, military, and other fields. As key components in ultrasonic applications, the characteristic parameters of ultrasonic transducers fundamentally determine the performance of ultrasonic systems. High-frequency ultrasonic transducers are small in size and require high [...] Read more.
Ultrasound is widely used in industry and the agricultural, biomedical, military, and other fields. As key components in ultrasonic applications, the characteristic parameters of ultrasonic transducers fundamentally determine the performance of ultrasonic systems. High-frequency ultrasonic transducers are small in size and require high precision, which puts forward higher requirements for sensor design, material selection, and processing methods. In this paper, a three-dimensional model of a high-frequency piezoelectric micromachined ultrasonic transducer (PMUT) is established based on the finite element method (FEM). This 3D model consists of a substrate, a silicon device layer, and a molybdenum-aluminum nitride-molybdenum (Mo-AlN-Mo) sandwich piezoelectric layer. The effect of the shape of the transducer’s vibrating membrane on the transmission performance was studied. Through a discussion of the parametric scanning of the key dimensions of the diaphragms of the three structures, it was concluded that the fundamental resonance frequency of the hexagonal diaphragm was higher than that of the circle and the square under the same size. Compared with the circular diaphragm, the sensitivity of the square diaphragm increased by 8.5%, and the sensitivity of the hexagonal diaphragm increased by 10.7%. The maximum emission sound-pressure level of the hexagonal diaphragm was 6.6 times higher than that of the circular diaphragm. The finite element results show that the hexagonal diaphragm design has great advantages for improving the transmission performance of the high-frequency PMUT. Full article
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15 pages, 11070 KiB  
Article
Flexible Ultrasonic Transducer Array with Bulk PZT for Adjuvant Treatment of Bone Injury
by Huicong Liu, Jiangjun Geng, Qifeng Zhu, Lue Zhang, Fengxia Wang, Tao Chen and Lining Sun
Sensors 2020, 20(1), 86; https://doi.org/10.3390/s20010086 - 22 Dec 2019
Cited by 37 | Viewed by 8097
Abstract
Flexible electronic devices are developing rapidly, especially in medical applications. This paper reports an arrayed flexible piezoelectric micromachined ultrasonic transducer (FPMUT) with a sandwich structure for adjuvant treatment of bone injury. To make the device conformable and stretchable for attaching to the skin [...] Read more.
Flexible electronic devices are developing rapidly, especially in medical applications. This paper reports an arrayed flexible piezoelectric micromachined ultrasonic transducer (FPMUT) with a sandwich structure for adjuvant treatment of bone injury. To make the device conformable and stretchable for attaching to the skin surface, the flexible substrate of polydimethylsiloxane (PDMS) was combined with the flexible metal line interconnection between the bulk lead zirconate titanate (PZT) arrays. Simulations and experiments were carried out to verify the resonant frequency and tensile property of the reported FPMUT device. The device had a resonant frequency of 321.15 KHz and a maximum sound pressure level (SPL) of 180.19 dB at the distance of 5 cm in water. In addition, detailed experiments were carried out to test its acoustic performance with different pork tissues, and the results indicated good ultrasound penetration. These findings confirm that the FPMUT shows unique advantages for adjuvant treatment of bone injury. Full article
(This article belongs to the Special Issue Ultrasonic Sensors 2019–2020)
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17 pages, 5704 KiB  
Article
Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding
by Guo-Hua Feng and Hua-Jin Liu
Sensors 2019, 19(21), 4696; https://doi.org/10.3390/s19214696 - 29 Oct 2019
Cited by 20 | Viewed by 5189
Abstract
This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather [...] Read more.
This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather than regular paper. The proposed microfabrication facilitated the PMUT to be able to generate ultrasonic waves with fundamental and harmonic resonances. The fourth-order resonances of the fabricated PMUT functionally operated at an ultrasonic spectrum of approximately 30 kHz as an ultrasonic emitter. The developed PMUT was paired with a microelectromechanical system (MEMS) microphone module for range-finding applications in the range of several tens of millimeters. A signal-processing scheme was developed to extract the representative pattern from the acquired signals that were emitted and received. The pattern enabled finding the distance between the PMUT and the microphone using time-of-flight and strength-variation technology. The developed PMUT-microphone pair demonstrated its range-finding performance, displaying an error of less than 0.7% using the time-of-flight method. Full article
(This article belongs to the Section Physical Sensors)
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15 pages, 5973 KiB  
Article
3D FEM Analysis of High-Frequency AlN-Based PMUT Arrays on Cavity SOI
by Wenjuan Liu, Leming He, Xubo Wang, Jia Zhou, Weijiang Xu, Nikolay Smagin, Malika Toubal, Hao Yu, Yuandong Gu, Jinghui Xu, Denis Remiens and Junyan Ren
Sensors 2019, 19(20), 4450; https://doi.org/10.3390/s19204450 - 14 Oct 2019
Cited by 29 | Viewed by 7010
Abstract
This paper presents three-dimensional (3D) models of high-frequency piezoelectric micromachined ultrasonic transducers (PMUTs) based on the finite element method (FEM). These models are verified with fabricated aluminum nitride (AlN)-based PMUT arrays. The 3D numerical model consists of a sandwiched piezoelectric structure, a silicon [...] Read more.
This paper presents three-dimensional (3D) models of high-frequency piezoelectric micromachined ultrasonic transducers (PMUTs) based on the finite element method (FEM). These models are verified with fabricated aluminum nitride (AlN)-based PMUT arrays. The 3D numerical model consists of a sandwiched piezoelectric structure, a silicon passive layer, and a silicon substrate with a cavity. Two types of parameters are simulated with periodic boundary conditions: (1) the resonant frequencies and mode shapes of PMUT, and (2) the electrical impedance and acoustic field of PMUT loaded with air and water. The resonant frequencies and mode shapes of an electrically connected PMUT array are obtained with a laser Doppler vibrometer (LDV). The first resonant frequency difference between 3D FEM simulation and the measurement for a 16-MHz PMUT is reasonably within 6%, which is just one-third of that between the analytical method and the measurement. The electrical impedance of the PMUT array measured in air and water is consistent with the simulation results. The 3D model is suitable for predicting electrical and acoustic performance and, thus, optimizing the structure of high-frequency PMUTs. It also has good potential to analyze the transmission and reception performances of a PMUT array for future compact ultrasonic systems. Full article
(This article belongs to the Section Physical Sensors)
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17 pages, 6559 KiB  
Article
The Effect of Electrical Impedance Matching on the Electromechanical Characteristics of Sandwiched Piezoelectric Ultrasonic Transducers
by Yuan Yang, Xiaoyuan Wei, Lei Zhang and Wenqing Yao
Sensors 2017, 17(12), 2832; https://doi.org/10.3390/s17122832 - 6 Dec 2017
Cited by 36 | Viewed by 9053
Abstract
For achieving the power maximum transmission, the electrical impedance matching (EIM) for piezoelectric ultrasonic transducers is highly required. In this paper, the effect of EIM networks on the electromechanical characteristics of sandwiched piezoelectric ultrasonic transducers is investigated in time and frequency domains, based [...] Read more.
For achieving the power maximum transmission, the electrical impedance matching (EIM) for piezoelectric ultrasonic transducers is highly required. In this paper, the effect of EIM networks on the electromechanical characteristics of sandwiched piezoelectric ultrasonic transducers is investigated in time and frequency domains, based on the PSpice model of single sandwiched piezoelectric ultrasonic transducer. The above-mentioned EIM networks include, series capacitance and parallel inductance (I type) and series inductance and parallel capacitance (II type). It is shown that when I and II type EIM networks are used, the resonance and anti-resonance frequencies and the received signal tailing are decreased; II type makes the electro-acoustic power ratio and the signal tailing smaller whereas it makes the electro-acoustic gain ratio larger at resonance frequency. In addition, I type makes the effective electromechanical coupling coefficient increase and II type makes it decrease; II type make the power spectral density at resonance frequency more dramatically increased. Specially, the electro-acoustic power ratio has maximum value near anti-resonance frequency, while the electro-acoustic gain ratio has maximum value near resonance frequency. It can be found that the theoretically analyzed results have good consistency with the measured ones. Full article
(This article belongs to the Section Physical Sensors)
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18 pages, 7024 KiB  
Article
PSpice Modeling of a Sandwich Piezoelectric Ceramic Ultrasonic Transducer in Longitudinal Vibration
by Xiaoyuan Wei, Yuan Yang, Wenqing Yao and Lei Zhang
Sensors 2017, 17(10), 2253; https://doi.org/10.3390/s17102253 - 30 Sep 2017
Cited by 35 | Viewed by 11340
Abstract
Sandwiched piezoelectric transducers are widely used, especially in high power applications. For more convenient analysis and design, a PSpice lossy model of sandwiched piezoelectric ultrasonic transducers in longitudinal vibration is proposed by means of the one-dimensional wave and transmission line theories. With the [...] Read more.
Sandwiched piezoelectric transducers are widely used, especially in high power applications. For more convenient analysis and design, a PSpice lossy model of sandwiched piezoelectric ultrasonic transducers in longitudinal vibration is proposed by means of the one-dimensional wave and transmission line theories. With the proposed model, the resonance and antiresonance frequencies are obtained, and it is shown that the simulations and measurements have good consistency. For the purpose of further verification the accuracy and application of the PSpice model, a pitch-catch setup and an experimental platform are built. They include two sandwiched piezoelectric ultrasonic transducers and two aluminum cylinders whose lengths are 20 mm and 100 mm respectively. Based on this pitch-catch setup, the impedance and transient analysis are performed. Compared with the measured results, it is shown that the simulated results have good consistency. In addition, the conclusion can be drawn that the optimal excitation frequency for the pitch-catch setup is not necessarily the resonance frequency of ultrasonic transducers, because the resonance frequency is obtained under no load. The proposed PSpice model of the sandwiched piezoelectric transducer is more conveniently applied to combine with other circuits such as driving circuits, filters, amplifiers, and so on. Full article
(This article belongs to the Section Physical Sensors)
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15 pages, 8321 KiB  
Article
The Use of Phononic Crystals to Design Piezoelectric Power Transducers
by Silvia Ronda, José Luis Aragón, Elvira Iglesias and Francisco Montero de Espinosa
Sensors 2017, 17(4), 729; https://doi.org/10.3390/s17040729 - 31 Mar 2017
Cited by 13 | Viewed by 5942
Abstract
It was recently proposed that the lateral resonances around the working resonance band of ultrasonic piezoelectric sandwich transducers can be stopped by a periodic array of circular holes drilled along the main propagation direction (a phononic crystal). In this work, the performance of [...] Read more.
It was recently proposed that the lateral resonances around the working resonance band of ultrasonic piezoelectric sandwich transducers can be stopped by a periodic array of circular holes drilled along the main propagation direction (a phononic crystal). In this work, the performance of different transducer designs made with this procedure is tested using laser vibrometry, electric impedance tests and finite element models (FEM). It is shown that in terms of mechanical vibration amplitude and acoustic efficiency, the best design for physiotherapy applications is when both, the piezoceramic and an aluminum capsule are phononic structures. The procedure described here can be applied to the design of power ultrasonic devices, physiotherapy transducers and other external medical power ultrasound applications where piston-like vibration in a narrow band is required. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)
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