Applications of Capacitive Micromachined Ultrasonic Transducers: A Comprehensive Review

Joseph, Jose; Ma, Bo; Khuri‐Yakub, Butrus T.

doi:10.1109/tuffc.2021.3112917

Cited by 55 publications

(23 citation statements)

References 88 publications

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“…V ISUALIZING the inside of the body by using ultrasound has mainly been limited to the hospital environment over the last three to four decades [1]. These hospital environments required high-quality ultrasound systems to make accurate diagnoses, leading to drastically improved performance of the ultrasound equipment [2]. However, in recent years, there has been an emerging low-end ultrasound market that accommodates new customer/patient demands, such as using ultrasound to continuously monitor the status of various visceral organs (i.e., heart, bladder), or as a handheld ultrasound system that can be connected to a smartphone to make on-site visualization in resource-limited settings [3], [4].…”

Section: Introductionmentioning

confidence: 99%

Modeling and Characterization of Pre-Charged Collapse-Mode CMUTs

Saccher

Kawasaki

Klootwijk

et al. 2023

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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Recently, the applications of ultrasound transducers expanded from high-end diagnostic tools to point of care diagnostic devices and wireless power receivers for implantable devices. These new applications additionally require that the transducer technology must comply to biocompatibility and manufacturing scalability. In this respect, Capacitive Micromachined Ultrasound Transducers (CMUTs) have a strong advantage compared to the conventional PZT based transducers. However, current CMUTs require a large DC bias voltage for their operation, which limits the miniaturizability of these devices. In this study, we propose a pre-charged collapse-mode CMUT for immersive applications that can operate without an external bias by means of a charge trapping Al 2 O 3 layer embedded in the dielectrics between the top and bottom electrodes. The built-in charge layer was analytically modeled and four layer stack combinations were investigated and characterized. The measurement results of the CMUTs were then used to fit the model and to quantify the amount and type of trapped charge. It was found that these devices polarize due to the ferroelectric-like behavior of the Al 2 O 3 , and the amount of charge stored in the charge-trapping layer was estimated to be approximately 0.02 C/m 2 . Their acoustic performance shows a transmit and receive sensitivity of 8.8 kPa/V and 13.1 V/MPa respectively. In addition, we show that increasing the charging temperature, the charging duration, and the charging voltage results in a higher amount of stored charge. Finally, results of ALT tests showed that these devices have a lifetime of more than 2.5 years at body temperature. CMUT, zero-bias CMUTs, collapse-mode CMUTs, ultrasound transducer INDEX TERMS

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Section: Introductionmentioning

confidence: 99%

Modeling and Characterization of Pre-Charged Collapse-Mode CMUTs

Saccher

Kawasaki

Klootwijk

et al. 2023

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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“…Micromachined ultrasonic transducers (MUTs) provide a promising solution for the aforementioned applications because of their miniature size (their whole size could scale down to several hundred micrometers), low power consumption, low fabrication cost, and easy integration with ICs 23 , 24 . Currently, MUTs can be categorized into two types: capacitive and piezoelectric micromachined ultrasonic transducers (CMUTs and PMUTs) 25 .…”

Section: Introductionmentioning

confidence: 99%

Noninvasive fluid bubble detection based on capacitive micromachined ultrasonic transducers

Yuan

et al. 2023

Microsyst Nanoeng

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Ultrasonic fluid bubble detection is important in industrial controls, aerospace systems and clinical medicine because it can prevent fatal mechanical failures and threats to life. However, current ultrasonic technologies for bubble detection are based on conventional bulk PZT-based transducers, which suffer from large size, high power consumption and poor integration with ICs and thus are unable to implement real-time and long-term monitoring in tight physical spaces, such as in extracorporeal membrane oxygenation (ECMO) systems and dialysis machines or hydraulic systems in aircraft. This work highlights the prospect of capacitive micromachined ultrasonic transducers (CMUTs) in the aforementioned application situations based on the mechanism of received voltage variation caused by bubble-induced acoustic energy attenuation. The corresponding theories are established and well validated using finite element simulations. The fluid bubbles inside a pipe with a diameter as small as 8 mm are successfully measured using our fabricated CMUT chips with a resonant frequency of 1.1 MHz. The received voltage variation increases significantly with increasing bubble radii in the range of 0.5–2.5 mm. Further studies show that other factors, such as bubble positions, flow velocities, fluid medium types, pipe thicknesses and diameters, have negligible effects on fluid bubble measurement, demonstrating the feasibility and robustness of the CMUT-based ultrasonic bubble detection technique.

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“…A CMUT is a sensor based on a capacitor architecture, with a fixed and a moving electrode actuated by electrostatic forces [9], [10]. CMUT applications range from volatile organic compounds detection, to medical therapy and ultrasound imaging [11]. T-M noise is an intrinsic phenomenon occurring in CMUTs [12]- [14].…”

Section: Introductionmentioning

confidence: 99%

Thermal-Mechanical Noise Modeling and Measurements of a Row-Column Addressed CMUT Probe

Merrien

Boulme²,

Certon

2022

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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Thermal-Mechanical (T-M) noise is a natural phenomenon occurring in Capacitive Micromachined Ultrasonic Transducers (CMUT). T-M noise is a value of great interest because it is linked to the minimal detectable pressure of a transducer and can also serve as a convenient characterization tool. Indeed, the general behavior of a CMUT array is translated through its T-M noise which does not require any external applied source to be assessed. However, T-M noise is difficult to measure, often time requires a dedicated measurement chain and is mostly based on spectrum analyzers in a carefully controlled environment. In this paper, we present a temporal technique to characterize the T-M noise of CMUT-based arrays with a commercially available amplifier and a digital oscilloscope. The approach is applied to an air coupled Row-Column Addressed (RCA) matrix array, for which the elements cannot be measured with traditional microprobes systems. This task is performed using a Printed Circuit Board (PCB) dedicated to the characterization of RCA arrays and designed to drive rows and columns individually. Noise Power Spectral Density (PSD) modeling of the complete measurement chain is achieved using a lumped-parameter model of the RCA array element and using the amplifier gain, electrical impedance, and noise characteristics. Measurements obtained with the signal analyzer and the temporal method are in good agreement with the model. The presented characterization technique can be extended to other micromachined ultrasonic transducer probe architectures, technologies, and amplification systems.

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Applications of Capacitive Micromachined Ultrasonic Transducers: A Comprehensive Review

Cited by 55 publications

References 88 publications

Modeling and Characterization of Pre-Charged Collapse-Mode CMUTs

Modeling and Characterization of Pre-Charged Collapse-Mode CMUTs

Noninvasive fluid bubble detection based on capacitive micromachined ultrasonic transducers

Thermal-Mechanical Noise Modeling and Measurements of a Row-Column Addressed CMUT Probe

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