Design and Fabrication of 1D CMUT Arrays for Dual-Mode Dual-Frequency Acoustic Angiography Applications

When microbubble contrast agents are excited at low frequencies (less than 5 MHz), they resonate and produce higher-order harmonics due to their nonlinear behavior. We propose a novel scheme with a capacitive micromachined ultrasonic transducer (CMUT) array to receive high-frequency microbubble harm...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2023-12, p.1-1
Main Authors: Annayev, Muhammetgeldi, Minhaj, Tamzid Ibn, Adelegan, Oluwafemi J., Yamaner, Feysel Yalcin, Dayton, Paul A., Oralkan, Omer
Format: Article
Language:English
Subjects:
Acoustic angiography (AA)
Acoustics
Angiography
Bandwidth
capacitive micromachined ultrasonic transducer (CMUT)
Dual-mode dual-frequency array
Finite element analysis
Fluids
Frequency control
glass substrate
Time-frequency analysis
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Summary:When microbubble contrast agents are excited at low frequencies (less than 5 MHz), they resonate and produce higher-order harmonics due to their nonlinear behavior. We propose a novel scheme with a capacitive micromachined ultrasonic transducer (CMUT) array to receive high-frequency microbubble harmonics in collapse mode and to transmit a low-frequency high-pressure pulse by releasing the CMUT plate from collapse and pull it back to collapse again in the same transmit-receive cycle. By patterning and etching the substrate to create glass spacers in the device cavity we can reliably operate the CMUT in collapse mode and receive high-frequency signals. Previously, we demonstrated a single-element CMUT with spacers operating in the described fashion. In this paper, we present the design and fabrication of a dual-mode, dual-frequency 1D CMUT array with 256 elements. We present two different insulating glass spacer designs in rectangular cells for the collapse mode. For the device with torus-shaped spacers, the 3 dB receive bandwidth is from 8 MHz to 17 MHz, and the transmitted maximum peak-to-peak pressure from 32 elements at 4 mm focal depth was 2.12 MPa with a 1.21 MPa peak negative pressure, which corresponds to a mechanical index (MI) of 0.58 at 4.3 MHz. For the device with line-shaped spacers, the 3 dB receive bandwidth at 150 V DC bias extends from 10.9 MHz to 19.2 MHz. By increasing the bias voltage to 180 V, the 3 dB bandwidth shifts, and extends from 11.7 MHz to 20.4 MHz. The transmitting maximum peak-to-peak pressure with 32 elements at 4 mm was 2.06 MPa with a peak negative pressure of 1.19 MPa, which corresponds to an MI of 0.62 at 3.7 MHz.
ISSN:0885-3010
1525-8955
DOI:10.1109/TUFFC.2023.3342011