Capacitive micromachined ultrasonic transducers with vented cavities
Abstract/Contents
- Abstract
- Capacitive micromachined ultrasonic transducers (CMUTs) are increasingly seen as a better alternative than piezoelectric transducers for many ultrasound applications. Ultrasonic flow metering presents one such case where CMUTs are much better suited. Due to their lower mechanical impedance, CMUTs are more efficient at coupling sound into a fluid medium than piezoelectric transducers. Unlike piezoelectric transducers which suffer from depoling at temperatures above their Curie point, CMUTs can easily be used in higher temperatures. This should make CMUTs ideal candidates for ultrasonic flow metering in extreme environments such as those that exist in flare stacks, high temperature steam lines in industrial plants, etc. Despite these benefits, conventional CMUTs are not suited for the highly variable pressure conditions that many flowmeters have to operate under. CMUTs with vented or pressurized cavities can overcome this limitation. This dissertation presents the design and modeling for such CMUTs. A reliable fabrication process for CMUTs vented through the plate or through the substrate is also presented. The fluid squeeze film formed in the cavity between the CMUT plate and the substrate provides a way to control the bandwidth and sensitivity of such CMUTs. The dissertation presents CMUTs with bandwidth ranging from 1% to over 20% in air. These CMUTs were tested under a pressure of up to 20 bar and maintained good bandwidth and SNR. The dissertation also discusses the importance of packaging for CMUTs vented through the substrate and presents a way to utilize acoustic resonances in the package for maintaining a steady operating frequency under varying pressure. The wide bandwidth of such CMUTs can be utilized in many other application of ultrasound in air. The dissertation briefly discussed the application of these CMUTs for thermoacoustic imaging as well as for gesture sensing.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Apte, Nikhil |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering. |
| Primary advisor | Kenny, Thomas William |
| Primary advisor | Khuri-Yakub, Butrus T, 1948- |
| Thesis advisor | Kenny, Thomas William |
| Thesis advisor | Khuri-Yakub, Butrus T, 1948- |
| Thesis advisor | Arbabian, Amin |
| Advisor | Arbabian, Amin |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Nikhil Apte. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Nikhil Prakash Apte
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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