Frequency Tuning of Collapse-Mode Capacitive Micromachined Ultrasonic Transducer

Pekař, Martin; Dittmer, Wendy U.; Mihajlović, Nenad; Soest, Gijs van; Jong, Nico de

doi:10.1016/j.ultras.2016.10.002

Cited by 26 publications

(19 citation statements)

References 14 publications

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“…Apart from the plates, aluminum bond pads providing contact to the top or bottom electrodes are created on the side of the array to allow for wire bonding. More information on the patented fabrication of the CMUT can be found in [33], [24]. The complete layer stack including the layer materials is shown in Figure 1.…”

Section: A Cmut Fabricationmentioning

confidence: 99%

“…CMUTs are made of thin membranes which are essentially parallel plate capacitors with a gap between the plates. The acoustic properties can be dynamically adjusted by changing the DC bias voltage [24], [25]. Depending on the applied DC voltage, a CMUT works in either conventional or collapse mode, with considerably different acoustic and received noise behavior [26], [27].…”

Section: Introductionmentioning

confidence: 99%

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Real-Time Coded Excitation Imaging Using a CMUT-Based Side Looking Array for Intravascular Ultrasound

Zangabad

Bosch

Mastik

et al. 2021

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Intravascular ultrasound (IVUS) is a wellestablished diagnostic method that provides images of the vessel wall and atherosclerotic plaques. We investigate the potential for phased-array IVUS utilizing Coded Excitation (CE) for improving the penetration depth and image signal-to-noise ratio (SNR). It is realized on a new experimental broadband Capacitive Micromachined Ultrasound Transducer (CMUT) array, operated in collapse mode, with 96 elements placed at the circumference of a catheter tip with 1.2 mm diameter. We characterized the array performance for CE imaging and showed that the-6 dB device bandwidth at 30 V DC biasing is 25 MHz with 20 MHz center frequency, with a transmit sensitivity of 37 kPa/V at that frequency. We designed a linear frequency modulation code to improve penetration depth by compensating high-frequency attenuation while preserving resolution by a mismatched filter reconstruction. We imaged a wire phantom and a human coronary artery plaque. By assessing the image quality of the reconstructed wire phantom image, we achieved 60 µm and 70 µm axial resolution using the short pulse and coded signal, respectively and gained 8 dB in SNR for coded excitation. Our developed system shows 20 frames per second, pixel-based beam-formed, real-time IVUS images.

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Section: A Cmut Fabricationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real-Time Coded Excitation Imaging Using a CMUT-Based Side Looking Array for Intravascular Ultrasound

Zangabad

Bosch

Mastik

et al. 2021

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…By applying an AC signal to the two plates, the distance between them changes generating US. An additional DC voltage can be applied either to tune the center frequency or to increase the amplitude of the US [11].…”

Section: A Sample Preparationmentioning

confidence: 99%

Pressure measurement of geometrically curved ultrasound transducer array for spatially specific stimulation of the vagus nerve

Kawasaki

Giagka

Haas

et al. 2019

2019 9th International IEEE/EMBS Conference on Neural Engineering (NER)

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Vagus nerve stimulators currently on the market can treat epilepsy and depression. Recent clinical trials show the potential for vagus nerve stimulation (VNS) to treat epilepsy, autoimmune disease, and traumatic brain injury. As we explore the benefits of VNS, it is expected that more possibilities for a new treatment will emerge in the future. However, existing VNS relies on electrical stimulation, whose limited selectivity (due to its poor spatial resolution) does not allow for any control over which therapeutic effect to induce. We hypothesize that by localizing the stimulation to fascicular level within the vagus nerve with focused ultrasound (US), it is possible to induce selective therapeutic effects with less side effects. A geometrically curve US transducer array that is small enough to wrap around the vagus nerve was fabricated. An experiment was conducted in water, with 48 US elements curved in a 1 mm radius and excited at 15 MHz to test the focusing capabilities of the device. The results show that the geometrical curvature focused the US to an area with a width and height of 110 µm and 550 µm. This will be equivalent to only 2.1% of the cross section of the vagus nerve, showing the potential of focused US to stimulate individual neuronal fibers within the vagus nerve selectively.

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“…First, the CMUT wafer is covered with a metal shield to reduce the coupling. A low noise OPAMP (MAX4475) 6 in a shield is placed right next to CMUT with R f = 1 G and C f = 1 pF as its parallel feedback impedance. CMUT is connected directly to the inverting input while the noninverting input of the OPAMP is connected to the ground.…”

Section: B Receive Sensitivity Performance Measurementsmentioning

confidence: 99%

“…These 2-D arrays can be integrated with electronics in the form of a 3-D multichip module by flip-chip bonding [5]. Recently [6], tuning of the center frequency of collapsedmode CMUT is investigated for inter-cardiac echo imaging. The center frequency of a collapsed CMUT is tuned between 8.7 MHz and 15.3 MHz by varying the DC bias.…”

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confidence: 99%

Optimization of a Collapsed Mode CMUT Receiver for Maximum Off-Resonance Sensitivity

Khan

Tasdelen

et al. 2018

J. Microelectromech. Syst.

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We propose an airborne collapse capacitive micromachined ultrasonic transducer (CMUT) as a practical viable ultrasound transducer capable of providing a stable performance at the off-resonance frequencies. Traditional practice is to bias the CMUT plate close to collapse voltage to achieve high coupling coefficient and sense the incoming ultrasound as an open-circuit receive voltage signal of the transducer or shortcircuit receive current (SCRC). Maintaining CMUT plate in the vicinity of collapse threshold is rather difficult. In this paper, an analytic approach to design an airborne collapsedmode CMUT for maximum off-resonance sensitivity is presented. We use small-signal circuit model to evaluate the performance of a collapsed CMUT for varying operating conditions. CMUT operational parameters that yield the highest off-resonance SCRC are directly obtained from performance design curves. Collapsed CMUT plate is then biased in a critical biasing region that produces a stable and maximum off-resonance sensitivity. We experimentally verify and measure a stable sensitivity of a fabricated collapsed CMUT cell of −60 dB V/Pa at 100 kHz when biased between 50 to 65 V. We characterize our linear circuit model performance against the measured performance of collapsed CMUT in air within 4-dB tolerance. [2018-0058] Index Terms-CMUT, collapsed CMUT sensitivity, critical biasing region, off-resonance, small-signal circuit model. I. INTRODUCTION O WING to standard silicon integrated circuit (IC) fabrication technology and potential for integration with electronics, CMUTs have proved to be a viable technology in medical ultrasound. For example, the first pulse-echo 128-element, 1-D linear CMUT array was fabricated using simple photolithography process and was characterized with a wider bandwidth and higher sensitivity than piezoelectric ceramics in 2001 [1]. Commercial scanners using 1-D CMUT arrays are also reported to have produced clinical-quality

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Frequency Tuning of Collapse-Mode Capacitive Micromachined Ultrasonic Transducer

Cited by 26 publications

References 14 publications

Real-Time Coded Excitation Imaging Using a CMUT-Based Side Looking Array for Intravascular Ultrasound

Real-Time Coded Excitation Imaging Using a CMUT-Based Side Looking Array for Intravascular Ultrasound

Pressure measurement of geometrically curved ultrasound transducer array for spatially specific stimulation of the vagus nerve

Optimization of a Collapsed Mode CMUT Receiver for Maximum Off-Resonance Sensitivity

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