scholarly journals PMMA-Based Wafer-Bonded Capacitive Micromachined Ultrasonic Transducer for Underwater Applications

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 319 ◽  
Author(s):  
Mansoor Ahmad ◽  
Ayhan Bozkurt ◽  
Omid Farhanieh
Keyword(s):  
Wafer Bonding ◽  
Sacrificial Layer ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Single Element ◽  
Element Analysis ◽  
Laboratory Equipment ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Dry Etch

This article presents a new wafer-bonding fabrication technique for Capacitive Micromachined Ultrasonic Transducers (CMUTs) using polymethyl methacrylate (PMMA). The PMMA-based single-mask and single-dry-etch step-bonding device is much simpler, and reduces process steps and cost as compared to other wafer-bonding methods and sacrificial-layer processes. A low-temperature (< 180 ∘ C ) bonding process was carried out in a purpose-built bonding tool to minimize the involvement of expensive laboratory equipment. A single-element CMUT comprising 16 cells of 2.5 mm radius and 800 nm cavity was fabricated. The center frequency of the device was set to 200 kHz for underwater communication purposes. Characterization of the device was carried out in immersion, and results were subsequently validated with data from Finite Element Analysis (FEA). Results show the feasibility of the fabricated CMUTs as receivers for underwater applications.

Design and Characterization of Capacitive Micromachined Ultrasonic Transducer

2006 ◽  
Vol 321-323 ◽  
pp. 132-135
Author(s):  
Bong Young Ahn ◽  
Ki Bok Kim ◽  
Hae Won Park ◽  
Young Joo Kim ◽  
Yong Seok Kwak
Keyword(s):  
Sacrificial Layer ◽  
Ultrasonic Transducer ◽  
Medical Engineering ◽  
Single Element ◽  
Air Atmosphere ◽  
Engineering Society ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
X 32 ◽  
2D Array

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.

scholarly journals Fabrication of 2-D Capacitive Micromachined Ultrasonic Transducer (CMUT) Array through Silicon Wafer Bonding

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 99
Author(s):  
Ziyuan Wang ◽  
Changde He ◽  
Wendong Zhang ◽  
Yifan Li ◽  
Pengfei Gao ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Silicon Wafer ◽  
Wafer Bonding ◽  
High Reliability ◽  
Ultrasonic Transducer ◽  
Silicon Film ◽  
Center Frequency ◽  
Single Element ◽  
Flow Monitoring ◽  
Static Capacitance

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.

Design and Experiment of Capacitive Micromachined Ultrasonic Transducer Array for High-Frequency Underwater Imaging

2020 ◽  
Vol 13 ◽  
Author(s):  
Yuanyu Yu ◽  
Jiujiang Wang ◽  
Xin Liu ◽  
Sio Hang Pun ◽  
Weibao Qiu ◽  
...  
Keyword(s):  
Ultrasound Imaging ◽  
High Frequency ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Design Parameters ◽  
Underwater Imaging ◽  
Release Process ◽  
Steel Wires ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Frequency Ultrasound

Background:: Ultrasound is widely used in the applications of underwater imaging. Capacitive micromachined ultrasonic transducer (CMUT) is a promising candidate to the traditional piezoelectric ultrasonic transducer. In underwater ultrasound imaging, better resolutions can be achieved with a higher frequency ultrasound. Therefore, a CMUT array for high-frequency ultrasound imaging is proposed in this work. Methods:: Analytical methods are used to calculate the center frequency in water and the pull-in voltage for determining the operating point of CMUT. Finite element method model was developed to finalize the design parameters. The CMUT array was fabricated with a five-mask sacrificial release process. Results:: The CMUT array owned an immersed center frequency of 2.6 MHz with a 6 dB fractional bandwidth of 123 %. The pull-in voltage of the CMUT array was 85 V. An underwater imaging experiment was carried out with the target of three steel wires. Conclusion:: In this study, we have developed CMUT for high-frequency underwater imaging. The experiment showed that the CMUT can detect the steel wires with the diameter of 100 μm and the axial resolution was 0.582 mm, which is close to one wavelength of ultrasound in 2.6 MHz.

scholarly journals An Investigation of Silica Aerogel to Reduce Acoustic Crosstalk in CMUT Arrays

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1459
Author(s):  
Varshitha Yashvanth ◽  
Sazzadur Chowdhury
Keyword(s):  
Silica Aerogel ◽  
Ultrasonic Transducer ◽  
Fluid Interface ◽  
Fractional Bandwidth ◽  
Neighboring Element ◽  
Element Analysis ◽  
Average Improvement ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Scholte Wave ◽  
Fea Simulation

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.

scholarly journals Advances in Capacitive Micromachined Ultrasonic Transducers

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 152 ◽  
Author(s):  
Kevin Brenner ◽  
Arif Ergun ◽  
Kamyar Firouzi ◽  
Morten Rasmussen ◽  
Quintin Stedman ◽  
...  
Keyword(s):  
Review Paper ◽  
Rapid Development ◽  
Ultrasonic Transducer ◽  
Ultrasonic Transducers ◽  
Imaging Systems ◽  
Future Trends ◽  
Levels Of Abstraction ◽  
Commercial Success ◽  
Capacitive Micromachined Ultrasonic Transducers ◽  
Capacitive Micromachined Ultrasonic Transducer

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.

Fabrication of Capacitive Micromachined Ultrasonic Transducer Arrays With Isolation Trenches Using Anodic Wafer Bonding

2015 ◽  
Vol 15 (9) ◽  
pp. 5177-5184 ◽  
Author(s):  
Ravindra Mukhiya ◽  
Aditi ◽  
K. Prabakar ◽  
M. Raghuramaiah ◽  
J. Jayapandian ◽  
...  
Keyword(s):  
Wafer Bonding ◽  
Ultrasonic Transducer ◽  
Transducer Arrays ◽  
Capacitive Micromachined Ultrasonic Transducer

scholarly journals Single-Shot Waterless Low-Profile Photoacoustic System: Near-Field Volumetric Imaging In Vivo for Blood Vessels Based on Capacitive Micromachined Ultrasonic Transducer (CMUT)

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 995 ◽  
Author(s):  
Won Choi ◽  
Young Kim ◽  
Hyeong Jo ◽  
Joo Pyun ◽  
Soo Kwon ◽  
...  
Keyword(s):  
Tissue Characterization ◽  
Imaging System ◽  
Ultrasonic Transducer ◽  
Near Field ◽  
Center Frequency ◽  
Single Shot ◽  
Living Body ◽  
Low Profile ◽  
Capacitive Micromachined Ultrasonic Transducer

Intensive research on photoacoustics (PA) for imaging of the living human body, including the skin, vessels, and tumors, has recently been conducted. We propose a PA measurement system based on a capacitive micromachined ultrasonic transducer (CMUT) with waterless coupling, short measurement time (<1 s), backward light irradiation, and a low-profile ultrasonic receiver unit (<1 cm). We fabricate a 64-element CMUT ring array with 6.2 mm diameter and 10.4 MHz center frequency in air, and 100% yield and uniform element response. To validate the PA tissue characterization, we employ pencil lead and red ink as solid and liquid models, respectively, and a living body to target moles and vessels. The system implements a near-field imaging system consisting of a 6 mm polydimethylsiloxane (PDMS) matching layer between the object and CMUT, which has a 3.7 MHz center frequency in PDMS. Experiments were performed in a waterless contact on the PDMS and the laser was irradiated with a 1 cm diameter. The experimental results show the feasibility of this near-field PA imaging system for position and depth detection of skin, mole, vessel cells, etc. Therefore, a system applicable to a low-profile compact biomedical device is presented.

scholarly journals Development of High-Frequency (>60 MHz) Intravascular Ultrasound (IVUS) Transducer by Using Asymmetric Electrodes for Improved Beam Profile

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4414 ◽  
Author(s):  
Jin Sung ◽  
Jong Jeong
Keyword(s):  
Intravascular Ultrasound ◽  
Performance Degradation ◽  
Beam Profile ◽  
Center Frequency ◽  
Single Element ◽  
Aperture Size ◽  
Element Analysis ◽  
Signal Line ◽  
Asymmetric Electrodes ◽  
Penetration Depths

In most commercial single-element intravascular ultrasound (IVUS) transducers, with 20 MHz to 40 MHz center frequencies, a conductive adhesive is used to bond a micro-sized cable for the signal line to the surface of the transducer aperture (<1 mm × 1 mm size) where ultrasound beam is generated. Therefore, the vibration of the piezoelectric layer is significantly disturbed by the adhesive with the signal line, thereby causing problems, such as reduced sensitivity, shortened penetration depth, and distorted beam profile. This phenomenon becomes more serious as the center frequency of the IVUS transducer is increased, and the aperture size becomes small. Therefore, we propose a novel IVUS acoustic stack employing asymmetric electrodes with conductive and non-conductive backing blocks. The purpose of this study is to verify the extent of performance degradation caused by the adhesive with the signal line, and to demonstrate how much performance degradation can be minimized by the proposed scheme. Finite element analysis (FEA) simulation was conducted, and the results show that −3 dB, −6 dB, and −10 dB penetration depths of the conventional transducer were shortened by 20%, 25%, and 19% respectively, while those of the proposed transducer were reduced only 3%, 4%, and 0% compared with their ideal transducers which have the same effective aperture size. Besides, the proposed transducer improved the −3 dB, −6 dB, and −10 dB penetration depths by 15%, 12%, and 10% respectively, compared with the conventional transducer. We also fabricated a 60 MHz IVUS transducer by using the proposed technique, and high-resolution IVUS B-mode (brightness mode) images were obtained. Thus, the proposed scheme can be one of the potential ways to provide more uniform beam profile resulting in improving the signal to noise ratio (SNR) in IVUS image.

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