Journal articles: 'CMUT'

1

Yildiz, Fikret, Tadao Matsunaga, and Yoichi Haga. "Fabrication and Packaging of CMUT Using Low Temperature Co-Fired Ceramic." Micromachines 9, no. 11 (October 27, 2018): 553. http://dx.doi.org/10.3390/mi9110553.

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This paper presents fabrication and packaging of a capacitive micromachined ultrasonic transducer (CMUT) using anodically bondable low temperature co-fired ceramic (LTCC). Anodic bonding of LTCC with Au vias-silicon on insulator (SOI) has been used to fabricate CMUTs with different membrane radii, 24 µm, 25 µm, 36 µm, 40 µm and 60 µm. Bottom electrodes were directly patterned on remained vias after wet etching of LTCC vias. CMUT cavities and Au bumps were micromachined on the Si part of the SOI wafer. This high conductive Si was also used as top electrode. Electrical connections between the top and bottom of the CMUT were achieved by Au-Au bonding of wet etched LTCC vias and bumps during anodic bonding. Three key parameters, infrared images, complex admittance plots, and static membrane displacement, were used to evaluate bonding success. CMUTs with a membrane thickness of 2.6 µm were fabricated for experimental analyses. A novel CMUT-IC packaging process has been described following the fabrication process. This process enables indirect packaging of the CMUT and integrated circuit (IC) using a lateral side via of LTCC. Lateral side vias were obtained by micromachining of fabricated CMUTs and used to drive CMUTs elements. Connection electrodes are patterned on LTCC side via and a catheter was assembled at the backside of the CMUT. The IC was mounted on the bonding pad on the catheter by a flip-chip bonding process. Bonding performance was evaluated by measurement of bond resistance between pads on the IC and catheter. This study demonstrates that the LTCC and LTCC side vias scheme can be a potential approach for high density CMUT array fabrication and indirect integration of CMUT-IC for miniature size packaging, which eliminates problems related with direct integration.

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Zhang, Pei Yu, and Yan Li. "Fabrication of Combined Capacitive Micromachined Ultrasound Transducers with Release Method." Advanced Materials Research 740 (August 2013): 416–21. http://dx.doi.org/10.4028/www.scientific.net/amr.740.416.

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A novel combined capacitive micromachined ultrasound transducer (CMUT) with release method was proposed and fabricated with. The combined CMUT has alternating low and high-frequency elements. Several different combined patterns of CMUTs were offered. The performances of CMUTs are strongly dependent on the geometrical properties of the single cells and their arrangement within each element as well. Finite element simulations are used for analysis, design, and optimization of CMUT cells to predict device performance. Electrostatic interactions for 3-D coupled-field simulations are also performed to help investigate the electro-mechanical properties of the CMUTs. Feasibility devices are then fabricated using chromium as a sacrificial release material. The top membrane is built using a sandwich structure to ensure the formation of large size membranes with low stress.

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Zhang, Rui, Wendong Zhang, Changde He, Jinlong Song, Linfeng Mu, Juan Cui, Yongmei Zhang, and Chenyang Xue. "Design of capacitive micromachined ultrasonic transducer (CMUT) linear array for underwater imaging." Sensor Review 36, no. 1 (January 18, 2016): 77–85. http://dx.doi.org/10.1108/sr-05-2015-0076.

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Purpose – The purpose of this paper was to develop a novel capacitive micromachined ultrasonic transducer (CMUT) reception and transmission linear array for underwater imaging at 400 kHz. Compared with traditional CMUTs, the developed transducer array offers higher electromechanical coupling coefficient and higher directivity performance. Design/methodology/approach – The configuration of the newly developed CMUT reception and transmission array was determined by the authors’ previous research into new element structures with patterned top electrodes and into directivity simulation analysis. Using the Si-Silicon on insulator (Si-SOI) bonding technique and the principle of acoustic impedance matching, the CMUT array was fabricated and packaged. In addition, underwater imaging system design and testing based on the packaged CMUT 1 × 16 array were completed. Findings – The simulation results showed that the optimized CMUT array configuration was selected. Furthermore, the designed configuration of the CMUT 1 × 16 linear array was good enough to guarantee high angular resolution. The underwater experiments were conducted to demonstrate that this CMUT array can be of great benefit in imaging applications. Practical implications – Based on our research, the CMUT linear array has good directivity and good impedance matching with water and can be used for obstacle avoidance, distance measurement and imaging underwater. Originality/value – This research provides a basis for CMUT directivity theory and array design. CMUT array presented in this paper has good directivity and has been applied in the underwater imaging, resulting in a huge market potential in underwater detection systems.

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Brenner, Kevin, Arif Ergun, Kamyar Firouzi, Morten Rasmussen, Quintin Stedman, and Butrus Khuri–Yakub. "Advances in Capacitive Micromachined Ultrasonic Transducers." Micromachines 10, no. 2 (February 23, 2019): 152. http://dx.doi.org/10.3390/mi10020152.

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Capacitive micromachined ultrasonic transducer (CMUT) technology has enjoyed rapid development in the last decade. Advancements both in fabrication and integration, coupled with improved modelling, has enabled CMUTs to make their way into mainstream ultrasound imaging systems and find commercial success. In this review paper, we touch upon recent advancements in CMUT technology at all levels of abstraction; modeling, fabrication, integration, and applications. Regarding applications, we discuss future trends for CMUTs and their impact within the broad field of biomedical imaging.

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Sharma, Rashmi, Rekha Agarwal, Ashwani Kumar Dubey, and Anil Arora. "Design and Analysis of Capacitive Micromachined Ultrasonic Transducer." Recent Patents on Engineering 13, no. 2 (May 27, 2019): 108–16. http://dx.doi.org/10.2174/1872212112666180214141506.

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Background:Objective:To simulate a Micromechanical systems (MEMS) based CMUT working as a transmitter with the existing design and provide comparison within the possible architectural geometries.Methods:FEM simulation software COMSOL is used to simulate the 3D model of the transducer radiating in the air. The classical thin-plate theory is employed to solve for CMUT with a circular shape which is sufficient when the ratio of the diameter to thickness of the plate is very large, an aspect common in CMUTs. The Galerkin-weighted residual technique is used to get a solution for thin plate equation with the presumption that the deflections are small in comparison to the thickness of the plate.Results:The resonant frequency of CMUT with different geometries have been calculated. The deflection of membrane with applied DC bias is shown along with collapse voltage calculation. The generated ultrasound is shown with the AC bias superimposed on the DC bias. The capacitance change with the increasing DC voltage is discussed. The deflection of membrane is maximum as the resonance frequency is proved.Conclusion:The review of Capacitive Micromachined Ultrasonic Transducer architectures with different shapes is highlighted. The working behavior of CMUT with suitable dimension is simulated in 3D providing researcher data to wisely choose the CMUT prior to the fabrication. The CMUT is prioritized on various characteristics like wafer area utilization, deflection percentage within the cavity and durability of the transducer.

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Tripathi, Sudhanshu, Rekha Agarwal, Rashmi Vashisth, and Devraj Singh. "Capacitive micromachined ultrasonic transducers: Transmission evaluation with different membrane materials and dimensions." tm - Technisches Messen 88, no. 4 (March 18, 2021): 251–59. http://dx.doi.org/10.1515/teme-2020-0073.

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Abstract Capacitive micromachined ultrasonic transducers (CMUTs) are dominant in generating and receiving acoustic signals. CMUT transmission efficiency solely depends upon the membrane material utilized. This work presents the structural examination of receiving and transmitting characteristics of CMUT with divergent membrane materials, namely Silicon (Si), Silicon Nitride ( Si 3 N 4 {\mathrm{Si}_{3}}{\text{N}_{4}} ), Indium Phosphide (InP), Zinc Oxide (ZnO), and Polysilicon (Poly-Si). The analysis includes the membrane deflection, pull-in voltage, output pressure, resonant frequency and capacitance modification with variable DC voltage. It has been found that InP gives the pull-in voltage comparable to Si in the receiving mode and have more transduction efficiency in transmitting mode. Effect of dimensions of CMUT on pull-in voltage and resonant frequency are also discussed. The major contribution lies in the analytical and estimation study of CMUT for appropriate membrane material selection meant for transmission and reception in the field of pressure sensing application.

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Liu, Xin, Yuanyu Yu, Jiujiang Wang, Sio Hang Pun, Mang I. Vai, and Peng Un Mak. "An Analytical Model for Bandwidth Enhancement of Air-Coupled Unsealed Helmholtz Structural CMUTs." Journal of Sensors 2019 (April 17, 2019): 1–16. http://dx.doi.org/10.1155/2019/3896965.

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Capacitive micromachined ultrasonic transducers (CMUTs) were reported to own high potential in air-coupled ultrasonic applications such as noncontact nondestructive examination and gas flow measurement. The unsealed CMUTs which utilized the squeeze film effect were reported to overcome the narrow output pressure bandwidth of the conventional sealed CMUTs in air operation. This kind of unsealed CMUTs can also be regarded as Helmholtz resonators. In this work, we present the air-coupled unsealed Helmholtz structural CMUTs which utilize both the squeeze film effect and the Helmholtz resonant effect to enhance the output pressure bandwidth. Based on the mechanism of vibration coupling between membrane and air pistons in membrane holes, we propose an analytical model to aid the design process of this kind of CMUTs. We also use finite element method (FEM) to investigate this kind of CMUTs for our analytical model validation. The FEM results show that the significant bandwidth enhancement can be achieved when the Helmholtz resonant frequency is designed close to the fundamental resonant frequency of the CMUT membrane. Compared with the conventional sealed CMUT cell, the 4-hole unsealed Helmholtz structural CMUT cell improves both the 3-dB fractional bandwidth and SPL-bandwidth product around 35 times. Furthermore, it is found that, with more holes under the same hole area ratio or with a smaller ratio of the cavity height to the viscous boundary layer thickness, the Helmholtz resonant effect becomes weaker and thus the output pressure bandwidth decreases.

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Oevermann, Jorge, Peter Weber, and Steffen H. Tretbar. "Encapsulation of Capacitive Micromachined Ultrasonic Transducers (CMUTs) for the Acoustic Communication between Medical Implants." Sensors 21, no. 2 (January 9, 2021): 421. http://dx.doi.org/10.3390/s21020421.

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The aim of this work was to extend conventional medical implants by the possibility of communication between them. For reasons of data security and transmitting distances, this communication should be realized using ultrasound, which is generated and detected by capacitive micromachined ultrasonic transducers (CMUTs). These offer the advantage of an inherent high bandwidth and a high integration capability. To protect the surrounding tissue, it has to be encapsulated. In contrast to previous results of other research groups dealing with the encapsulation of CMUTs, the goal here is to integrate the CMUT into the housing of a medical implant. In this work, CMUTs were designed and fabricated for a center frequency of 2 MHz in water and experimentally tested on their characteristics for operation behind layers of Polyether ether ketone (PEEK) and titanium, two typical materials for the housings of medical implants. It could be shown that with silicone as a coupling layer it is possible to operate a CMUT behind the housing of an implant. Although it changes the characteristics of the CMUT, the setup is found to be well suited for communication between two transducers over a distance of at least 8 cm.

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Oevermann, Jorge, Peter Weber, and Steffen H. Tretbar. "Encapsulation of Capacitive Micromachined Ultrasonic Transducers (CMUTs) for the Acoustic Communication between Medical Implants." Sensors 21, no. 2 (January 9, 2021): 421. http://dx.doi.org/10.3390/s21020421.

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The aim of this work was to extend conventional medical implants by the possibility of communication between them. For reasons of data security and transmitting distances, this communication should be realized using ultrasound, which is generated and detected by capacitive micromachined ultrasonic transducers (CMUTs). These offer the advantage of an inherent high bandwidth and a high integration capability. To protect the surrounding tissue, it has to be encapsulated. In contrast to previous results of other research groups dealing with the encapsulation of CMUTs, the goal here is to integrate the CMUT into the housing of a medical implant. In this work, CMUTs were designed and fabricated for a center frequency of 2 MHz in water and experimentally tested on their characteristics for operation behind layers of Polyether ether ketone (PEEK) and titanium, two typical materials for the housings of medical implants. It could be shown that with silicone as a coupling layer it is possible to operate a CMUT behind the housing of an implant. Although it changes the characteristics of the CMUT, the setup is found to be well suited for communication between two transducers over a distance of at least 8 cm.

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10

Pirouz, Amirabbas, and F. Degertekin. "An Analysis Method for Capacitive Micromachined Ultrasound Transducer (CMUT) Energy Conversion during Large Signal Operation." Sensors 19, no. 4 (February 20, 2019): 876. http://dx.doi.org/10.3390/s19040876.

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With Capacitive Micromachined Ultrasound Transducers (CMUTs) increasingly being used for high intensity, large signal ultrasound applications and several drive methods being proposed, the efficiency of these devices in this operation regime have not been quantitatively evaluated. Since well-known frequency and capacitance-based coupling coefficients definitions are not valid for large signal, nonlinear operation, an energy-based definition should be used. In this paper, an expression for mechanical energy in a CMUT is obtained based on the assumption that CMUT is a linear time varying capacitor in all regimes of operation. This expression is evaluated by the help of an experimentally verified nonlinear CMUT model to define an energy conversion ratio (ECR) which can be considered as a coupling coefficient valid for all regimes of operation. This parameter is validated in the small signal regime and then used to evaluate CMUT performance with various large drive signals. The quantitative modeling results show that CMUTs do not need DC bias to achieve high efficiency large signal transduction: AC only signals at half the operation frequency with amplitudes beyond the collapse voltage can provide efficiencies (ECR) above 0.9 with harmonic content below −25 dB. Based on these results, ECR variation with membrane geometry and parasitic capacitance are given as examples for device optimization. The overall modeling approach is also qualitatively validated by experiments.

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Ahn, Bong Young, Ki Bok Kim, Hae Won Park, Young Joo Kim, and Yong Seok Kwak. "Design and Characterization of Capacitive Micromachined Ultrasonic Transducer." Key Engineering Materials 321-323 (October 2006): 132–35. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.132.

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As cMUTs (capacitive Micromachined Ultrasonic Transducer) offer numerous advantages over traditional transducers in terms of efficiency, bandwidth, and cost, they are expected to replace piezoelectric transducers in many applications. In particular, 2D-array cMUTs have aroused great interest in the medical engineering society because of their ability to materialize a true volumetric ultrasonic image. In this study, single element cMUTs with 32 x 32 and 64 x 64 cells were successfully fabricated. The diameter and thickness of the membrane are 35 and 1000 nm, respectively, with a sacrificial layer thickness of 600 nm. The electric characteristics of the fabricated cMUT were measured. Tests on the efficiencies of the cMUT in terms of wave generation and in terms of detection according to the bias and pulse voltage were performed in an air atmosphere.

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Wang, Jiujiang, Xin Liu, Yuanyu Yu, Yao Li, Ching-Hsiang Cheng, Shuang Zhang, Peng-Un Mak, Mang-I. Vai, and Sio-Hang Pun. "A Review on Analytical Modeling for Collapse Mode Capacitive Micromachined Ultrasonic Transducer of the Collapse Voltage and the Static Membrane Deflections." Micromachines 12, no. 6 (June 18, 2021): 714. http://dx.doi.org/10.3390/mi12060714.

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Analytical modeling of capacitive micromachined ultrasonic transducer (CMUT) is one of the commonly used modeling methods and has the advantages of intuitive understanding of the physics of CMUTs and convergent when modeling of collapse mode CMUT. This review article summarizes analytical modeling of the collapse voltage and shows that the collapse voltage of a CMUT correlates with the effective gap height and the electrode area. There are analytical expressions for the collapse voltage. Modeling of the membrane deflections are characterized by governing equations from Timoshenko, von Kármán equations and the 2D plate equation, and solved by various methods such as Galerkin’s method and perturbation method. Analytical expressions from Timoshenko’s equation can be used for small deflections, while analytical expression from von Kármán equations can be used for both small and large deflections.

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Ding, Qi, Hongliang Wang, Hanqiang Zhang, Xiao Huang, Xiaolei Sun, Zhenjie Qin, Rui Ren, Jiajun Zhu, Changde He, and Wendong Zhang. "Research on Novel CMUTs for Detecting Micro-Pressure with Ultra-High Sensitivity and Linearity." Micromachines 12, no. 11 (October 30, 2021): 1340. http://dx.doi.org/10.3390/mi12111340.

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Capacitive micromachined ultrasonic transducers (CMUTs) have been indispensable owing to their resonance characteristics in the MHz frequency range. However, the inferior pressure sensitivity and linearity of traditional CMUTs themselves cannot meet the actual demands of micro-pressure measurements. In this paper, two novel CMUTs are proposed for the first time to improve the measuring performance of micro-pressure in the range of 0–10 kPa. The core concept of the enhancement is strengthening membrane deformability by partly adjusting the CMUT framework under the combined action of electrostatic force and uniform pressure. Two modified structures of an inverted frustum cone-like cavity and slotted membrane are presented, respectively, and a finite element model (FEM) of CMUT was constructed and analyzed using COMSOL Multiphysics 5.5. The results demonstrate that the maximum displacement and pressure sensitivity are improved by 16.01% and 30.79% for the frustum cone-like cavity and 104.22% and 1861.31% for the slotted membrane, respectively. Furthermore, the results show that the width uniformity of the grooves does not influence the characteristics of the membrane, which mainly depend on the total width of the grooves, greatly enriching design flexibility. In brief, the proposed structural designs can significantly improve the micro-pressure measurement performance of the CMUT, which will accelerate the rapid breakthrough of technical barriers in the fields of aerospace, industry control, and other sensing domains.

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Wang, Hongliang, Xiao Huang, Lijun Yu, Qi Ding, Hanqiang Zhang, Changde He, and Wendong Zhang. "Hybrid Cell Structure for Wideband CMUT: Design Method and Characteristic Analysis." Micromachines 12, no. 10 (September 29, 2021): 1180. http://dx.doi.org/10.3390/mi12101180.

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Capacitive micromachined ultrasonic transducer (CMUT) is an ultrasonic transducer based on the microelectromechanical system (MEMS). Wideband CMUT has good application prospects in ultrasonic imaging, ultrasonic identification, flow measurement, and nondestructive testing due to its excellent characteristics. This paper studies the method of increasing the bandwidth of the CMUT, proposes the structure of the wideband CMUT with a hybrid cell structure, and analyzes the design principles and characteristics of the wideband CMUT structure. By changing the cell spacing and the number of cells of different sizes composing the CMUT, we analyze the simulation of the effect of the spacing and number on the CMUT bandwidth, thereby optimizing the bandwidth characteristics of the CMUT. Next, the selection principle of the main structural parameters of the wideband CMUT is analyzed. According to the proposed principle, the CMUT in the air and water are designed and simulated. The results prove that both the air and water CMUT meet the design requirements. The design rules obtained in this paper can provide theoretical guidance for the selection of the main structural parameters of the wideband CMUT.

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McAnulla, Craig, Claire A. Woodall, Ian R. McDonald, Alex Studer, Stephane Vuilleumier, Thomas Leisinger, and J. Colin Murrell. "Chloromethane Utilization Gene Cluster fromHyphomicrobium chloromethanicum Strain CM2T and Development of Functional Gene Probes To Detect Halomethane-Degrading Bacteria." Applied and Environmental Microbiology 67, no. 1 (January 1, 2001): 307–16. http://dx.doi.org/10.1128/aem.67.1.307-316.2001.

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ABSTRACT Hyphomicrobium chloromethanicum CM2T, an aerobic methylotrophic member of the α subclass of the classproteobacteria, can grow with chloromethane as the sole carbon and energy source. H. chloromethanicum possesses an inducible enzyme system for utilization of chloromethane, in which two polypeptides (67-kDa CmuA and 35-kDa CmuB) are expressed. Previously, four genes, cmuA, cmuB, cmuC, andpurU, were shown to be essential for growth ofMethylobacterium chloromethanicum on chloromethane. ThecmuA and cmuB genes were used as probes to identify homologs in H. chloromethanicum. A cmugene cluster (9.5 kb) in H. chloromethanicum contained 10 open reading frames: folD (partial), pduX,orf153, orf207, orf225,cmuB, cmuC, cmuA, fmdB, and paaE (partial). CmuA from H. chloromethanicum (67 kDa) showed high identity to CmuA fromM. chloromethanicum and contains an N-terminal methyltransferase domain and a C-terminal corrinoid-binding domain. CmuB from H. chloromethanicum is related to a family of methyl transfer proteins and to the CmuB methyltransferase fromM. chloromethanicum. CmuC from H. chloromethanicum shows identity to CmuC from M. chloromethanicum and is a putative methyltransferase.folD codes for a methylene-tetrahydrofolate cyclohydrolase, which may be involved in the C1 transfer pathway for carbon assimilation and CO2 production, and paaE codes for a putative redox active protein. Molecular analyses and some preliminary biochemical data indicated that the chloromethane utilization pathway in H. chloromethanicum is similar to the corrinoid-dependent methyl transfer system in M. chloromethanicum. PCR primers were developed for successful amplification of cmuA genes from newly isolated chloromethane utilizers and enrichment cultures.

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Yu, Yuanyu, Jiujiang Wang, Xin Liu, Sio Hang Pun, Shuang Zhang, Ching-Hsiang Cheng, Kin Fong Lei, Mang I. Vai, and Peng Un Mak. "Experimental Characterization of an Embossed Capacitive Micromachined Ultrasonic Transducer Cell." Micromachines 11, no. 2 (February 20, 2020): 217. http://dx.doi.org/10.3390/mi11020217.

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Capacitive Micromachined Ultrasonic Transducer (CMUT) is a promising ultrasonic transducer in medical diagnosis and therapeutic applications that demand a high output pressure. The concept of a CMUT with an annular embossed pattern on a membrane working in collapse mode is proposed to further improve the output pressure. To evaluate the performance of an embossed CMUT cell, both the embossed and uniform membrane CMUT cells were fabricated in the same die with a customized six-mask sacrificial release process. An annular nickel pattern with the dimension of 3 μ m × 2 μ m (width × height) was formed on a full top electrode CMUT to realize an embossed CMUT cell. Experimental characterization was carried out with optical, electrical, and acoustic instruments on the embossed and uniform CMUT cells. The embossed CMUT cell achieved 27.1% improvement of output pressure in comparison to the uniform CMUT cell biased at 170 V voltage. The fractional bandwidths of the embossed and uniform CMUT cells were 52.5% and 41.8%, respectively. It substantiated that the embossed pattern should be placed at the vibrating center of the membrane for achieving a higher output pressure. The experimental characterization indicated that the embossed CMUT cell has better operational performance than the uniform CMUT cell in collapse region.

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Wang, Ziyuan, Changde He, Wendong Zhang, Yifan Li, Pengfei Gao, Yanan Meng, Guojun Zhang, et al. "Fabrication of 2-D Capacitive Micromachined Ultrasonic Transducer (CMUT) Array through Silicon Wafer Bonding." Micromachines 13, no. 1 (January 8, 2022): 99. http://dx.doi.org/10.3390/mi13010099.

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Capacitive micromachined ultrasound transducers (CMUTs) have broad application prospects in medical imaging, flow monitoring, and nondestructive testing. CMUT arrays are limited by their fabrication process, which seriously restricts their further development and application. In this paper, a vacuum-sealed device for medical applications is introduced, which has the advantages of simple manufacturing process, no static friction, repeatability, and high reliability. The CMUT array suitable for medical imaging frequency band was fabricated by a silicon wafer bonding technology, and the adjacent array devices were isolated by an isolation slot, which was cut through the silicon film. The CMUT device fabricated following this process is a 4 × 16 array with a single element size of 1 mm × 1 mm. Device performance tests were conducted, where the center frequency of the transducer was 3.8 MHz, and the 6 dB fractional bandwidth was 110%. The static capacitance (29.4 pF) and center frequency (3.78 MHz) of each element of the array were tested, and the results revealed that the array has good consistency. Moreover, the transmitting and receiving performance of the transducer was evaluated by acoustic tests, and the receiving sensitivity was −211 dB @ 3 MHz, −213 dB @ 4 MHz. Finally, reflection imaging was performed using the array, which provides certain technical support for the research of two-dimensional CMUT arrays in the field of 3D ultrasound imaging.

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Zhang, Wen, Hui Zhang, Shijiu Jin, and Zhoumo Zeng. "A Two-Dimensional CMUT Linear Array for Underwater Applications: Directivity Analysis and Design Optimization." Journal of Sensors 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/5298197.

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Capacitive micromachined ultrasonic transducers (CMUTs) are one of the promising MEMS devices. This paper proposed an integrated vibration membrane structure to design a two-dimensional CMUT linear array for underwater applications. The operation frequencies for different medium have been calculated and simulated, which are 2.5 MHz in air and 0.7 MHz in water. The directivity analyses for the CMUT cell, subarray, and linear array have been provided. According to the product theorems, the directivity function of the complex array is obtained using a combination of the directivity functions of certain simple structures. Results show that the directivity of a CMUT cell is weak due to the small size, but the directivity of the designed linear array is very strong. Influential parameters of the linear array have been discussed, including the cell numbers, the adjacent distance, and the operation medium. In order to further suppress the side lobe interference and improve the resolution and the imaging quality of the imaging system, several weighting methods are used for optimization and comparison. Satisfactory side lobe suppression results are obtained, which can meet the actual requirements.

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Ronnekleiv, A. "CMUT array modeling through free acoustic CMUT modes and analysis of the fluid CMUT interface through Fourier transform methods." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 52, no. 12 (December 2005): 2173–84. http://dx.doi.org/10.1109/tuffc.2005.1563261.

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Wang, Hongliang, Xiangjun Wang, Changde He, and Chenyang Xue. "Reception characteristics investigation and measurement of capacitive micromachined ultrasonic transducer." Sensor Review 40, no. 2 (September 9, 2019): 237–46. http://dx.doi.org/10.1108/sr-06-2019-0146.

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Purpose As a new type of ultrasonic transducer with significant advantages, capacitive micromachined ultrasonic transducer (CMUT) has good application prospect. The reception characteristic of the CMUT is one of the important factors determining the application effect. This paper aims to study the reception characteristics of CMUT. Design/methodology/approach In this paper, the state equation is deduced and the analysis model is established in SIMULINK environment based on the lumped parameter system model of the CMUT cell. Based on this analysis model, the influencing factors of CMUT reception characteristics are studied and investigated, and the time-domain and frequency-domain characteristics are investigated in detail. Findings The analysis results show that parameters directly affect the reception characteristics of the CMUT, such as direct current (DC) bias voltage, input sound pressure amplitude and frequency. At the same time, the measurement system is built and the reception characteristics are verified. Originality/value This paper provides an effective method for rapid analyzing the reception characteristics of CMUT. These results provide an important theoretical basis and reference for further optimization of CMUT structure design, and lay a good foundation for the practical application measurement.

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Ye, Lei, Jian Li, Hui Zhang, Dongmei Liang, and Zhuochen Wang. "An Integrated Front-end Circuit Board for Air-Coupled CMUT Burst-Echo Imaging." Sensors 20, no. 21 (October 28, 2020): 6128. http://dx.doi.org/10.3390/s20216128.

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To conduct burst-echo imaging with air-coupled capacitive micromachined ultrasonic transducers (CMUTs) using the same elements in transmission and reception, this work proposes a dedicated and integrated front-end circuit board design to build an imaging system. To the best of the authors’ knowledge, this is the first air-coupled CMUT burst-echo imaging using the same elements in transmission and reception. The reported front-end circuit board, controlled by field programmable gate array (FPGA), consisted of four parts: an on-board pulser, a bias-tee, a T/R switch and an amplifier. Working with our 217 kHz 16-element air-coupled CMUT array under 100 V DC bias, the front-end circuit board and imaging system could achieve 22.94 dB signal-to-noise ratio (SNR) in burst-echo imaging in air, which could represent the surface morphology and the three-dimensional form factor of the target. In addition, the burst-echo imaging range of our air-coupled CMUT imaging system, which could work between 52 and 273 mm, was discussed. This work suggests good potential for ultrasound imaging and gesture recognition applications.

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He, Changde, Binzhen Zhang, Chenyang Xue, Wendong Zhang, and Shengdong Zhang. "Wafer-Bonding Fabricated CMUT Device with Parylene Coating." Micromachines 12, no. 5 (May 4, 2021): 516. http://dx.doi.org/10.3390/mi12050516.

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The advantages of the capacitive micromachined ultrasound transducer (CMUT) technology have provided revolutionary advances in ultrasound imaging. Extensive research on CMUT devices for high-frequency medical imaging applications has been conducted because of strong demands and fabrication realization by using standard silicon IC fabrication technology. However, CMUT devices for low-frequency underwater imaging applications have been rarely researched because it is difficult to fabricate thick membrane structures through depositing processes using standard IC fabrication technology due to stress-related problems. To address this shortcoming, in this paper, a CMUT device with a 2.83-μm thick silicon membrane is proposed and fabricated. The CMUT device is fabricated using silicon fusion wafer-bonding technology. A 5-μm thick Parylene-C is conformally deposited on the device for immersion measurement. The results show that the fabricated CMUT can transmit an ultrasound wave, receive an ultrasound wave, and have pulse-echo measurement capability. The ability of the device to emit and receive ultrasonic waves increases with the bias voltage but does not depend on the voltage polarity. The results demonstrate the viability of the fabricated CMUT in low-frequency applications from the perspectives of the device structure, fabrication, and characterization. This study presents the potential of the CMUT for underwater ultrasound imaging applications.

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Zhang, Rui, Lei Zhao, Dan Xie, Jinlong Song, Wendong Zhang, Lihu Pan, and Yanhua Zhang. "Performance simulation and testing of capacitive micro-machined ultrasonic transducer." Sensor Review 39, no. 4 (July 15, 2019): 554–66. http://dx.doi.org/10.1108/sr-01-2019-0015.

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Purpose This study aims to simulate and test the performance of a transmitting and receiving capacitive micro-machined ultrasonic transducer (CMUT). Aimed at detecting demand of the CMUT, a matched integrated adjustment circuit was designed through analyzing processing methods of transducer’s weak echo signal. Design/methodology/approach Based on the analysis of CMUT array structure and work principle, the CMUT units are designed and the dynamic performance analysis of SIMULINK is given according to the demand of underwater detecting. A transceiver isolation circuit is used to make transmission mode and receiving mode separate. A detection circuit is designed based on the transimpedance amplifier to achieve extraction of high-frequency and weak signal. Findings Through experimentation, the effectiveness of the CMUT performance simulation and the transceiver integrated adjustment circuit were verified. In addition, the test showed that CMUT with 400 kHz frequency has wider bandwidth and better dynamic characteristics than other similar transducers. Originality/value This paper provides a theoretical basis and design reference for the development and application of CMUT technology.

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Goel, Chirag, Paul-Vahe Cicek, and Alexandre Robichaud. "Design and Implementation of Low-Voltage Tunable Capacitive Micro-Machined Transducers (CMUT) for Portable Applications." Micromachines 13, no. 10 (September 26, 2022): 1598. http://dx.doi.org/10.3390/mi13101598.

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Capacitive micromachined ultrasonic transducers (CMUT) are MEMS-based transducers with advantages over conventional ultrasonic transducers, such as their small size, the ease of integration with semiconductor electronics, and batch fabrication. In this study, the effect of different membrane topologies on the displacement, resonant frequency, and output pressure of the CMUT membrane is investigated in the transmission mode in an air environment. A novel structural-support feature, the rocker stem, is introduced, where the membrane is weakly held to the substrate in order to minimize mechanical constraints. Four different CMUT topologies are designed and assessed to analyze the impacts of topological variations. A new CMUT array configuration is also designed to provide an approach for maximizing CMUT density. This study aims to contribute to efficient CMUT design and the determination of optimum structural parameters for portable applications in air.

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Kim, Bae-Hyung, Seungheun Lee, and Kang-Sik Kim. "Orthogonal Chirp Coded Excitation in a Capacitive Micro-machined Ultrasonic Transducer Array for Ultrasound Imaging: A Feasibility Study." Sensors 19, no. 4 (February 20, 2019): 883. http://dx.doi.org/10.3390/s19040883.

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It has been reported that the frequency bandwidth of capacitive micro-machined ultrasonic transducers (CMUTs) is relatively broader than that of other ceramic-based conventional ultrasonic transducers. In this paper, a feasibility study for orthogonal chirp coded excitation to efficiently make use of the wide bandwidth characteristic of CMUT array is presented. The experimental result shows that the two orthogonal chirps mixed and simultaneously fired in CMUT array can be perfectly separated in decoding process of the received echo signal without sacrificing the frequency bandwidth each chirp. The experimental study also shows that frequency band-divided orthogonal chirps are successfully compressed to two short pulses having the −6 dB axial beam-width of 0.26- and 0.31-micro second for high frequency and low frequency chirp, respectively. B-mode image simulations are performed using Field II to estimate the improvement of image quality assuming that the orthogonal chirps designed for the experiments are used for simultaneous transmission multiple-zone focusing (STMF) technique. The simulation results show that the STMF technique used in CMUT array can improve the lateral resolution up to 77.1% and the contrast resolution up to 74.7%, respectively. It is shown that the penetration depth also increases by more than 3 cm.

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Huang, Xiao, Hongliang Wang, and Lijun Yu. "Investigation on Design Theory and Performance Analysis of Vacuum Capacitive Micromachined Ultrasonic Transducer." Micromachines 12, no. 9 (September 19, 2021): 1127. http://dx.doi.org/10.3390/mi12091127.

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The capacitive micromachined ultrasonic transducer (CMUT), as a new acoustic-electric conversion element, has a promising application prospect. In this paper, the structure of the vacuum capacitive micromachined ultrasonic transducer is presented, and its performance-influencing factors are investigated. Firstly, the influencing factors of the performance parameters of the vacuum CMUT are analyzed theoretically based on the circular plate model and flat plate capacitance model, and the design principles of the structural parameters of the CMUT cell are proposed. Then, the finite element simulation software COMSOL Multiphysics is used to construct CMUT cell models with different membrane materials, membrane shapes, membrane radius thicknesses, and cavity heights for simulation verification. The results show that both the membrane parameters and the cavity heights affect the performance parameters of the Vacuum CMUT. In order to improve the efficiency of the CMUT, materials with low bending stiffness should be selected, and the filling factor of the membrane should be increased. In order to achieve high-transmission sound pressure, a smaller radius thickness and a larger cavity height should be selected. To achieve high reception sensitivity, a larger membrane radius thickness and a smaller cavity height should be selected. In order to obtain high fractional bandwidth, a larger membrane radius thickness should be selected. The results of this paper provide a basis for the design of Vacuum CMUT cell structure.

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Zhang, Tian, Wendong Zhang, Xingling Shao, Yuhua Yang, Zhihao Wang, Yang Wu, and Yu Pei. "A Study on Capacitive Micromachined Ultrasonic Transducer Periodic Sparse Array." Micromachines 12, no. 6 (June 11, 2021): 684. http://dx.doi.org/10.3390/mi12060684.

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Capacitive micromachined ultrasonic transducer (CMUT) is an ultrasonic transducer based on the microelectromechanical system (MEMS). CMUT elements are easily made into a high-density array, which will increase the hardware complexity. In order to reduce the number of active channels, this paper studies the grating lobes generated by CMUT periodic sparse array (PSA) pairs. Through the design of active element positions in the transmitting and receiving processes, the simulation results of effective aperture and beam patterns show that the common grating lobes (CGLs) generated by the transmit and receive array are eliminated. On the basis of point targets imaging, a CMUT linear array with 256 elements is used to carry out the PSA pairs experiment. Under the same sparse factor (SF), the optimal sparse array configuration can be selected to reduce the imaging artifacts. This conclusion is of great significance for the application of CMUT in three-dimensional ultrasound imaging.

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Chowdhury, Sazzadur. "A simple closed-form model to accurately calculate the electromechanical coupling coefficient of CMUTs." tm - Technisches Messen 88, no. 11 (October 20, 2021): 714–23. http://dx.doi.org/10.1515/teme-2021-0080.

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Abstract A simple highly accurate closed-form model to calculate the electromechanical coupling coefficient of a capacitive micromachined ultrasonic transducer (CMUT) is presented. The model exploits the electrostatic spring softening phenomenon to derive an expression for the energy converted from electrical to mechanical domain and includes the nonlinear change of the CMUT diaphragm stiffness during large deflections. The model has been validated by comparing the model predicted values with experimental results published elsewhere along with the results predicted by some existing models. The comparison shows that the model predicted values are in excellent agreement with experimental results. The model also enables one to quantify the effects of residual stress, bending, and nonlinear stretching of the diaphragm on the transduction efficiency of CMUTs without any computationally intensive finite element analysis method. The model resolves the ambiguity of the absence of electrostatic spring softening effect in some existing models.

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Wang, Hongliang, Yunfei Lv, Chaojie Wang, Xiangjun Wang, Changde He, Chenyang Xue, and Shuang He. "Simulation Analysis and Performance Testing Investigation of Capacitive Micromachined Ultrasonic Transducer." International Journal of Pattern Recognition and Artificial Intelligence 32, no. 09 (May 27, 2018): 1858004. http://dx.doi.org/10.1142/s0218001418580041.

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In various applications of ultrasonic waves, the ultrasonic transducer is the key device of ultrasonic testing and ultrasonic imaging. Compared with the traditional piezoelectric transducer, the capacitive micromachined ultrasonic transducer (CMUT) has many striking advantages, such as low impedance, high bandwidth, easy integration and low cost, and it is expected to become a next generation of mainstream products. In this paper, a CMUT structure for underwater-imaging applications is designed, and the finite element model is established by using COMSOL software, then the modal analysis, harmonic response analysis, electromechanical coupling analysis and transient analysis are carried out. As a consequence, the key parameters of CMUT are obtained, namely resonance frequency, voltage collapse and electromechanical coupling coefficient. For the processed CMUT line array consisting of 16 elements, a test system is built and the emission performance, receiving performance, directivity, bandwidth and preliminary imaging of the designed transducer are tested and analyzed. The results show that the designed CMUT array can meet the requirements of underwater-imaging applications.

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Qin, Yi, Weijie Sun, and John TW Yeow. "A robust control approach for MEMS capacitive micromachined ultrasonic transducer." Transactions of the Institute of Measurement and Control 41, no. 1 (March 26, 2018): 107–16. http://dx.doi.org/10.1177/0142331218757860.

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An optimal composite nonlinear feedback control method with integral sliding mode is presented in this paper. The controller extends the travel range of the micro-electromechanical system capacitive micromachined ultrasonic transducer (CMUT). Moreover, enhanced transient response and precise tracking performance is achieved. It is known that CMUT is inherently unstable which results in pull-in phenomenon and it is very sensitive to small perturbations, so one of the major problems is to stabilize the CMUT beyond the pull-in limit with the external disturbances. In addition, the input saturation problem is significant to CMUT. Based on that, a robust control scheme is derived using composite nonlinear feedback control law combined with integral sliding mode control law. Then all the tuning parameters for the proposed control method are converted into a minimization problem and solved by particle swarm optimization algorithm automatically. We verified the effectiveness through extending the travel range of the CMUT gap by three control methods which are proportional integral derivative, composite nonlinear feedback and the method we proposed. The stability and small range tracking performance with three control methods is compared on the pull-in position of CMUT. The simulations show that the proposed control method has desired tracking performance and robustness to external disturbance with input saturation.

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Ahrens, O., A. Buhrdorf, D. Hohlfeld, L. Tebje, and J. Binder. "Fabrication of gap-optimized CMUT." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 49, no. 9 (September 2002): 1321–29. http://dx.doi.org/10.1109/tuffc.2002.1041549.

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Zhang, Tian, Wendong Zhang, XingLing Shao, and Yang Wu. "Research on optimization sparse method for capacitive micromachined ultrasonic transducer array: heuristic algorithm." Sensor Review 41, no. 3 (June 21, 2021): 260–70. http://dx.doi.org/10.1108/sr-03-2021-0082.

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Purpose Because of the small size and high integration of capacitive micromachined ultrasonic transducer (CMUT) component, it can be made into large-scale array, but this lead to high hardware complexity, so the purpose of this paper is to use less elements to achieve better imaging results. In this research, an optimized sparse array is studied, which can suppress the side lobe and reduce the imaging artifacts compared with the equispaced sparse array with the same number of elements. Design/methodology/approach Genetic algorithm is used to sparse the CMUT linear array, and Kaiser window apodization is added to reduce imaging artifacts, the beam pattern and peak-to-side lobe ratio are calculated, point targets imaging comparisons are performed. Furthermore, a 256-elements CMUT linear array is used to carry out the imaging experiment of embedded mass and forearm blood vessel, and the imaging results are compared quantitatively. Findings Through the imaging comparison of embedded mass and forearm blood vessel, the feasibility of optimized sparse array of CMUT is verified, and the purpose of reducing the hardware complexity is achieved. Originality/value This research provides a basis for the large-scale CMUT array to reduce the hardware complexity and the amount of calculation. At present, the CMUT array has been used in medical ultrasound imaging and has huge market potential.

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Gao, Bizhen, Sai Zhang, Changde He, Renxin Wang, Yuhua Yang, Licheng Jia, Zhihao Wang, Yang Wu, Shumin Hu, and Wendong Zhang. "Research on Broadband Matching Method for Capacitive Micromachined Ultrasonic Transducers Based on PDMS/TiO2 Particles." Micromachines 13, no. 11 (October 26, 2022): 1827. http://dx.doi.org/10.3390/mi13111827.

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The study of impedance matching between a transducer and its working medium is an important part of acoustic transducer design. The traditional quarter wavelength matching (Q-matching) scheme is not suitable for broadband capacitive micromachined ultrasonic transducers. To mitigate this issue, a 0–3 composite broadband matching layer based on polydimethylsiloxane (PDMS) substrate/TiO2 particles is designed to achieve electrical insulation and efficient acoustic energy transfer of underwater capacitive micromachined ultrasonic transducer (CMUT) devices. In this work, the coherent potential approximation model is used to analyze the properties of 0–3 composite materials. Samples are prepared for performance testing to determine the proportion of TiO2 particles that enable the 0–3 composite materials to have the same longitudinal acoustic impedance as water. The CMUT device is packaged by a spin coating and pouring process, and its performance tests are carried out. The experimental results show that the central frequency of the transducer remains at 1.74 MHz, the −6 dB fractional bandwidth increases from 97.3% to 100.3%, the 3 dB directional main beam width increases from 8.3°to 10.3°, the side lobes decrease significantly, and the device has good reception sensitivity. These values imply that the 0–3 composite material has good matching performance, and this matching scheme has the advantages of high efficiency and wide bandwidth. This broadband matching method endows CMUTs with great advantages in underwater detection systems, and it facilitates underwater ultrasonic imaging of CMUT.

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Du, Yiheng, Changde He, Guowei Hao, Wendong Zhang, and Chenyang Xue. "Full-Differential Folded-Cascode Front-End Receiver Amplifier Integrated Circuit for Capacitive Micromachined Ultrasonic Transducers." Micromachines 10, no. 2 (January 25, 2019): 88. http://dx.doi.org/10.3390/mi10020088.

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This paper describes the design of a front-end receiver amplifier for capacitive micromachined ultrasonic transducer (CMUT). The proposed operational amplifier (op amp) consists of a full differential folded-cascode amplifier stage followed by a class AB output stage. A feedback resistor is applied between the input and the output of the op amp to make a transimpedance amplifier. We analyzed the equivalent circuit model of the CMUT element operating in the receiving mode and obtained the static output impedance and center frequency characteristics of the CMUT. The op amp gain, bandwidth, noise, and power consumption trade-oﬀs are discussed in detail. The amplifier was fabricated using GlobalFoundries 0.18-μm complementary metal-oxide-semiconductor (CMOS) technology. The open loop gain of the amplifier is approximately 65 dB, and its gain bandwidth product is approximately 29.5 MHz. The measured input reference noise current was 56 nA/√Hz@3 MHz. The amplifier chip area is 325 μm × 150 μm and the op amp is powered by 3.3 V, the static power consumption is 11 mW. We verified the correct operation of our amplifier with CMUT and echo-pulse shown that the CMUT center frequency is 3 MHz with 92% fractional bandwidth.

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Li, Yan, and Pei Yu Zhang. "Modeling and Modal Analysis on Capacitive Micromachined Ultrasound Transducers." Applied Mechanics and Materials 620 (August 2014): 300–303. http://dx.doi.org/10.4028/www.scientific.net/amm.620.300.

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The capacitive micromachined ultrasonic transducers with square and rectangular membranes were modeled for FEM simulation. The membrane is modeled as a thin plate clamped on all sides. Resonant frequencies and vibration modal analysis were carried out. The modes of CMUT with square and rectangular membranes are different. It can be basis for building CMUTs’ structure. Moreover, the resonant frequencies will vary with different side length and ratio of length/width of membrane.

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Yashvanth, Varshitha, and Sazzadur Chowdhury. "An Investigation of Silica Aerogel to Reduce Acoustic Crosstalk in CMUT Arrays." Sensors 21, no. 4 (February 19, 2021): 1459. http://dx.doi.org/10.3390/s21041459.

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This paper presents a novel technique to reduce acoustic crosstalk in capacitive micromachined ultrasonic transducer (CMUT) arrays. The technique involves fabricating a thin layer of diisocyanate enhanced silica aerogel on the top surface of a CMUT array. The silica aerogel layer introduces a highly nanoporous permeable layer to reduce the intensity of the Scholte wave at the CMUT-fluid interface. 3D finite element analysis (FEA) simulation in COMSOL shows that the developed technique can provide a 31.5% improvement in crosstalk reduction for the first neighboring element in a 7.5 MHz CMUT array. The average improvement of crosstalk level over the −6 dB fractional bandwidth was 22.1%, which is approximately 5 dB lower than that without an aerogel layer. The results are in excellent agreement with published experimental results to validate the efficacy of the new technique.

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Bensalem, Roufaida, Animesh Saha Shovan, Juan Morency Trudel, Hani H. Tawfik, Karim Allidina, Mohannad Y. Elsayed, Mounir Boukadoum, and Mourad N. El-Gamal. "Design of an Integrated Micro-Viscometer for Monitoring Engine Oil." Sensors 22, no. 14 (July 9, 2022): 5157. http://dx.doi.org/10.3390/s22145157.

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This paper proposes a novel integrated micro-viscometer for engine-oil monitoring. The final solution consists of a capacitive micromachined ultrasonic transducer (CMUT) and an application-specific integrated circuit (ASIC). The CMUT is used to generate and capture acoustic waves while immersed in engine oil. The low power transceiver ASIC is interfaced with the CMUT structure for actuation and reception. An integrated charge pump boosts the supply voltage from 3.3 to 22 V to generate the DC polarization voltage of the CMUT. The receiver has a power consumption of 72 µW with an input-referred noise current of 3.2pAHz and a bandwidth of 7 MHz. The CMUT array occupies an area of 3.5 × 1 mm, whereas the ASIC has a chip area of 1 × 1 mm. The system was tested using engine oils of different types and ages at different temperatures. Measurement results show a significant frequency shift due to the dynamic viscosity change that occurs as oil ages. A shift of −1.9 kHz/cP was measured, which corresponds to a shift of 33 Hz/mile. This work paves the way for high accuracy-integrated solutions for oil condition monitoring and is expected to play a significant role in a more economic and environmentally friendly usage of oil.

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Wang, Hongliang, Jiao Qu, Xiangjun Wang, Changde He, and Chenyang Xue. "Investigation and Analysis of Ultrasound Imaging Based on Linear CMUT Array." International Journal of Pattern Recognition and Artificial Intelligence 33, no. 08 (June 25, 2019): 1957004. http://dx.doi.org/10.1142/s0218001419570040.

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In the next generation of ultrasound imaging systems, Capacitive micromachined ultasonic transducer (CMUT) based on microelectromechanical systems (MEMS) is a promising research direction of transducers, which has wide application prospects. In this paper, based on the study of three imaging methods, including classical phased array (CPA) imaging, classical synthetic aperture (CSA) imaging and phased subarray (PSA) imaging, several different imaging schemes are designed for linear CMUT array, after that the performances of these imaging schemes are compared and analyzed. The effects of the three imaging methods are verified and analyzed based on the linear CMUT array. Through analysis, it is found that the image quality of the classical phased array imaging method is the best, the imaging quality of the above three imaging methods can be effectively improved by adopting the amplitude apodization and dynamic focusing method. The research results in this paper will provide theoretical basis and application reference for the design of ultrasonic imaging system based on linear CMUT array in the future.

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Draghi, Ferdinando, Pascal Lomoro, Chandra Bortolotto, Luca Mastrogirolamo, and Fabrizio Calliada. "Comparison between a new ultrasound probe with a capacitive micromachined transducer (CMUT) and a traditional one in musculoskeletal pathology." Acta Radiologica 61, no. 12 (March 4, 2020): 1653–60. http://dx.doi.org/10.1177/0284185120907983.

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Background The capacitive micromachined ultrasound transducer (CMUT) is a new ultrasound (US) probe manufactured by state-of-the-art cutting-edge semi-conductor micromachined electro-mechanical systems (MEMS) technology. Purpose To demonstrate the peculiar characteristics of each probe and the limitations that should be improved. Material and Methods This study was performed from March to April 2018. The only inclusion criterion was the presence of disease, so all patients with musculoskeletal, skin, and subcutaneous pathology were included. A total of 66 patients entered this study. The exams of each patient, with both probes, were evaluated retrospectively and independently by three radiologists. Panoramicity of the images, the definition of superficial structures (<2 cm of depth), the definition of deep structures (>2 cm), and Doppler signal were assessed. A 5-point scale was used for each parameter. Results A total of 89 pathologies were detected. The mean of score for 4G-CMUT was higher than L64 for the panoramicity of the images and the definition of the deep structures. Instead, the mean score for L64 was higher than for 4G-CMUT in the evaluation of superficial structures and Doppler signal. A statistically significant difference was found ( P < 0.05). Conclusion CMUT is a breakthrough in US technology. It allows the use of a single probe for different US examinations. The musculoskeletal, skin, and subcutaneous US can be evaluated with a piezoelectric linear transducer or CMUT. In the present study, the overall diagnostic performance was similar. Improvements in CMUT will provide even more dynamic and flexible imaging capabilities by a transducer, with a wider bandwidth.

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Degertekin, F. Levent. "Harmonic Cmut Devices And Fabrication Methods." Journal of the Acoustical Society of America 130, no. 3 (2011): 1781. http://dx.doi.org/10.1121/1.3636073.

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Atalar, Abdullah, Hayrettin Köymen, and H. Kaan Oğuz. "Rayleigh–bloch waves in CMUT arrays." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 61, no. 12 (December 2014): 2139–48. http://dx.doi.org/10.1109/tuffc.2014.006610.

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Li, Yu Ping, Chang De He, Juan Ting Zhang, Jin Long Song, Wen Dong Zhang, and Chen Yang Xue. "Design and Analysis of Capacitive Micromachined Ultrasonic Transducers Based on SU-8." Key Engineering Materials 645-646 (May 2015): 577–82. http://dx.doi.org/10.4028/www.scientific.net/kem.645-646.577.

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In this paper, a new capacitive micromachined ultrasonic transducer (CMUT) is designed by using SU-8 material, and the theory of elastic thin plate is used to deduce the relationship between the pressure and capacitance of the structure. Simulation has been done about SU-8 CMUT by finite element method software ANSYS. The deformation of CMUT under acoustic pressure, the relationship between frequency, thickness and sensitivity, as well as the acoustic impedance and reflection coefficient of SU-8 material also have been studied through the simulation. The results turn out that SU-8 has the advantages of big dynamic range, high sensitivity and small acoustic impedance, so it has broad application in the ultrasonic field.

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Jallouli, Aymen, Najib Kacem, and Joseph Lardies. "Investigations of the Effects of Geometric Imperfections on the Nonlinear Static and Dynamic Behavior of Capacitive Micomachined Ultrasonic Transducers." Micromachines 9, no. 11 (November 5, 2018): 575. http://dx.doi.org/10.3390/mi9110575.

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In order to investigate the effects of geometric imperfections on the static and dynamic behavior of capacitive micomachined ultrasonic transducers (CMUTs), the governing equations of motion of a circular microplate with initial defection have been derived using the von Kármán plate theory while taking into account the mechanical and electrostatic nonlinearities. The partial differential equations are discretized using the differential quadrature method (DQM) and the resulting coupled nonlinear ordinary differential equations (ODEs) are solved using the harmonic balance method (HBM) coupled with the asymptotic numerical method (ANM). It is shown that the initial deflection has an impact on the static behavior of the CMUT by increasing its pull-in voltage up to 45%. Moreover, the dynamic behavior is affected by the initial deflection, enabling an increase in the resonance frequencies and the bistability domain and leading to a change of the frequency response from softening to hardening. This model allows MEMS designers to predict the nonlinear behavior of imperfect CMUT and tune its bifurcation topology in order to enhance its performances in terms of bandwidth and generated acoustic power while driving the microplate up to 80% beyond its critical amplitude.

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Jung, Chan Yong, and Kwan Kyu Park. "Two-channel CMUT Chemical Sensor for Carbon Dioxide Detection." JOURNAL OF THE KOREAN SOCIETY FOR NONDESTRUCTIVE TESTING 39, no. 2 (April 30, 2019): 89–94. http://dx.doi.org/10.7779/jksnt.2019.39.2.89.

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Barauskas, Dovydas, Donatas Pelenis, Mindaugas Dzikaras, Marius Mikolajunas, Gailius Vanagas, and Darius Virzonis. "Inkjet-Printed Functionalization of CMUT-Based CO2 Sensors." Sensors 22, no. 6 (March 16, 2022): 2288. http://dx.doi.org/10.3390/s22062288.

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The trade-off between the functionalization shift of the informative parameters and sensitivity of capacitive micromachined ultrasound transducers (CMUT)-based CO2 sensors is addressed, and the CMUT surface modification process by thin inkjet-printed polyethyleneimine (PEI) films is optimized. It was shown that by the proper preparation of the active CMUT surface and properly diluted PEI solution, it is possible to minimize the functionalization shift of the resonance frequency and the quality of the resonance and preserve the sensitivity potential. So, after optimization, we demonstrated 23.2 kHz frequency shift readings of the sensor with 16 MHz nominal frequency while in the gas chamber and switching between pure N2 and CO2. After testing the sensors with different PEI film thickness, it was confirmed that a 200 nm average thickness of a PEI film is an optimum, because this is the practical limit of CO2 absorption depth at given conditions. Additionally, we note that modification of the hydrophilic/hydrophobic properties of the CMUT surface allows changing the nanoscale surface roughness of the printed PEI film and controlling the area resolution of the inkjet functionalization by reducing the diameter of a single dot down to 150 μm by a commercially available printer cartridge.

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Zhang, Wen, Hui Zhang, Fei Du, Jianchao Shi, Shijiu Jin, and Zhoumo Zeng. "Pull-In Analysis of the Flat Circular CMUT Cell Featuring Sealed Cavity." Mathematical Problems in Engineering 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/150279.

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Capacitive micromachined ultrasonic transducers (CMUTs) are one of the appealing MEMS devices. Most studies treat CMUTs as rigid plates vibrating in open air, ignoring the mechanical boundary conditions for simplification and resulting in cumulative errors in coupled fields. This paper presents a new analytical model for the pull-in characteristics of the flat circular CMUT cell featuring sealed cavity. Utilizing the plate theory coupled with Boyle’s law, the paper establishes a strong relation between the pressures inside the sealed cavity and the pull-in characteristics for the first time. Not only did we point out that the existence of the pressure inside the sealed cavity cannot be omitted, but we also quantified the direct effect of the pressure ratios on the pull-in phenomenon. The pull-in voltages increase while the pull-in ratios decrease with the pressure ratios of the pressure inside the sealed cavity to the ambient pressure. The proposed calculation process delivers a good approximation of the pull-in voltages and displacements, which are consistent with COMSOL simulation results. Particularly, the percentage error of our calculation process is 6.986% for the worst case. Therefore, our proposed analytical model accurately and efficiently predicts the pull-in characteristics and this paper offers new perspectives and reference value in designing and modeling the CMUTs.

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Daft, Christopher M. W. "PIEZOELECTRIC AND CMUT LAYERED ULTRASOUND TRANSDUCER ARRAY." Journal of the Acoustical Society of America 133, no. 4 (2013): 2520. http://dx.doi.org/10.1121/1.4800170.

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Unlugedik, Aslı, A. Tasdelen, Abdullah Atalar, and Hayrettin Koymen. "Designing transmitting CMUT cells for airborne applications." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 61, no. 11 (November 2014): 1899–910. http://dx.doi.org/10.1109/tuffc.2014.006457.

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Demirci, U., A. S. Ergun, O. Oralkan, M. Karaman, and B. T. Khuri-Yakub. "Forward-viewing CMUT arrays for medical imaging." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 51, no. 7 (July 2004): 887–95. http://dx.doi.org/10.1109/tuffc.2004.1320749.

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Certon, D., F. Teston, and F. Patat. "A finite difference model For cMUT devices." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 52, no. 12 (December 2005): 2199–210. http://dx.doi.org/10.1109/tuffc.2005.1563263.

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Journal articles on the topic 'CMUT'

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