Coupling Effects of Crosstalk and Parasitic Loss on Capacitive Micromachined Ultrasonic Transducers

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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Design and Fabrication of Wideband Air-Coupled Capacitive Micromachined Ultrasonic Transducers With Varying Width Annular-Ring and Spiral Cell Structures

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control ◽

10.1109/tuffc.2021.3076143 ◽

2021 ◽

pp. 1-1

Author(s):

Oluwafemi J. Adelegan ◽

Zachary A. Coutant ◽

Xun Wu ◽

Feysel Yalcin Yamaner ◽

Omer Oralkan

Keyword(s):

Ultrasonic Transducers ◽

Annular Ring ◽

Capacitive Micromachined Ultrasonic Transducers ◽

Cell Structures

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Capacitive micromachined ultrasonic transducers: Transmission evaluation with different membrane materials and dimensions

tm - Technisches Messen ◽

10.1515/teme-2020-0073 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Sudhanshu Tripathi ◽

Rekha Agarwal ◽

Rashmi Vashisth ◽

Devraj Singh

Keyword(s):

Resonant Frequency ◽

Material Selection ◽

Transmission Efficiency ◽

Ultrasonic Transducers ◽

Transduction Efficiency ◽

Membrane Material ◽

Structural Examination ◽

Membrane Materials ◽

Capacitive Micromachined Ultrasonic Transducers ◽

Output Pressure

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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