Deep-collapse operation of capacitive micromachined ultrasonic transducers

Date
2011
Authors
Olcum, S.
Yamaner F. Y.
Bozkurt, A.
Atalar, Abdullah
Advisor
Instructor
Source Title
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Print ISSN
0885-3010
Electronic ISSN
Publisher
IEEE
Volume
58
Issue
11
Pages
2475 - 2483
Language
English
Type
Article
Journal Title
Journal ISSN
Volume Title
Abstract

Capacitive micromachined ultrasonic transducers (CMUTs) have been introduced as a promising technology for ultrasound imaging and therapeutic ultrasound applications which require high transmitted pressures for increased penetration, high signal-to-noise ratio, and fast heating. However, output power limitation of CMUTs compared with piezoelectrics has been a major drawback. In this work, we show that the output pressure of CMUTs can be significantly increased by deep-collapse operation, which utilizes an electrical pulse excitation much higher than the collapse voltage. We extend the analyses made for CMUTs working in the conventional (uncollapsed) region to the collapsed region and experimentally verify the findings. The static deflection profile of a collapsed membrane is calculated by an analytical approach within 0.6% error when compared with static, electromechanical finite element method (FEM) simulations. The electrical and mechanical restoring forces acting on a collapsed membrane are calculated. It is demonstrated that the stored mechanical energy and the electrical energy increase nonlinearly with increasing pulse amplitude if the membrane has a full-coverage top electrode. Utilizing higher restoring and electrical forces in the deep-collapsed region, we measure 3.5 MPa peak-to-peak pressure centered at 6.8 MHz with a 106% fractional bandwidth at the surface of the transducer with a collapse voltage of 35 V, when the pulse amplitude is 160 V. The experimental results are verified using transient FEM simulations.

Course
Other identifiers
Book Title
Keywords
Analytical approach, Capacitive micromachined ultrasonic transducer, Collapse voltage, Electrical energy, Electrical force, Electrical pulse excitation, FEM simulations, Finite element method simulation, Fractional bandwidths, High signal-to-noise ratio, Mechanical energies, Output power, Piezoelectrics, Pulse amplitude, Restoring forces, Static deflections, Therapeutic ultrasound, Ultrasound imaging, Bandwidth, Fading, Finite element method, Power quality, Pulse amplitude modulation, Signal to noise ratio, Ultrasonics, Electric Capacitance, Ultrasonic therapy, Ultrasonography
Citation
Published Version (Please cite this version)