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You searched for subject:(Gravimetric sensing). Showing records 1 – 2 of 2 total matches.

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University of Waterloo

1. Zheng, Zhou. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Humidity Sensing.

Degree: 2019, University of Waterloo

In the last two decades, capacitive micromachined ultrasonic transducers (CMUTs) have proven themselves to be promising for various ultrasound imaging and chemical sensing applications. Although holding many benefits for ultrasound imaging, CMUTs have certain weaknesses such as the relatively low output pressure at transmission, which hinder their development in the diagnostic imaging application. In the sensing area, CMUTs have shown attractive features such as high mass sensitivity, miniaturized array configuration, and ease of functionalization. However, their potential for humidity sensing is less explored. The objectives of this thesis lie in two aspects. One is to offer a solution to overcome the limitation of low output pressure, and the other is to develop CMUTs as resonant gravimetric humidity sensors. The major efforts are made on the second task. For the first objective, a novel dual-element ultrasonic transducer is proposed. It incorporates two transducer technologies by using a circular piezoelectric element for ultrasound transmission and an annular CMUT element for reception. The hybrid transducer combines the broad bandwidth and high receive sensitivity of the CMUT and the high output power of the piezoelectric transducer to improve the overall sensitivity and axial resolution. The annular CMUT is designed, fabricated, and concentrically aligned with the piezoelectric probe via a custom housing. Immersion measurements show that the hybrid dual-element transducer improves the axial resolution by 25.58% and the signal-to-noise ratio by 8.55 dB over the commercial piezoelectric probe. For the second objective, a CMUT-based resonant humidity sensor is first developed with the direct wafer bonding technique. Graphene oxide (GO) is employed as the sensing material. Due to combination of the mass-sensitive CMUT and the moisture-sensitive GO, the sensor exhibits rapid response/recovery, good repeatability, and higher sensitivity than most of its competitors. The second generation of CMUT-based humidity sensors aims to further improve the relative humidity (RH) sensing performance by adopting the nitride-to-oxide wafer bonding technology for CMUT fabrication. In contrast to conventional wafer bonding CMUT processes that use expensive silicon-on-insulator (SOI) wafers to produce resonating membranes, the new process employs low-pressure chemical vapor deposition (LPCVD) silicon nitride as the membrane material. It provides thinner and lighter membranes, and thus more sensitive CMUT resonators. Additional benefits of the nitride-to-oxide wafer bonding technique are the reduced fabrication complexity and more controllable membrane thickness. Finally, a dual-frequency (10/14 MHz) CMUT is developed using this fabrication technique. It generates two RH response curves and can provide more accurate RH sensing. Due to the independence of the two resonance frequencies, the dual-frequency CMUT also shows great potential for identification of different chemicals. This thesis demonstrates that CMUT sensors can be strong…

Subjects/Keywords: CMUT; ultrasound; gravimetric sensor; humidity sensing; wafer bonding

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zheng, Z. (2019). Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Humidity Sensing. (Thesis). University of Waterloo. Retrieved from http://hdl.handle.net/10012/15037

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Zheng, Zhou. “Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Humidity Sensing.” 2019. Thesis, University of Waterloo. Accessed October 16, 2019. http://hdl.handle.net/10012/15037.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Zheng, Zhou. “Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Humidity Sensing.” 2019. Web. 16 Oct 2019.

Vancouver:

Zheng Z. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Humidity Sensing. [Internet] [Thesis]. University of Waterloo; 2019. [cited 2019 Oct 16]. Available from: http://hdl.handle.net/10012/15037.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Zheng Z. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Humidity Sensing. [Thesis]. University of Waterloo; 2019. Available from: http://hdl.handle.net/10012/15037

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Fu, Jenna L. Micromachined piezoelectric-on-silicon platform for resonant sensing and energy harvesting.

Degree: PhD, Electrical and Computer Engineering, 2013, Georgia Tech

A microelectromechanical systems (MEMS)-based environmental monitoring platform was presented in this dissertation. All devices were realized using thin-film piezoelectric-on-substrate (TPoS) technology, which provides a path to integrate various functionalities on a single substrate with MEMS components. TPoS resonators exhibit high quality factors (Qs) in air and are capable of low-power oscillator implementation, which further qualifies such a platform for mobile and portable systems. To validate the TPoS platform, gravimetric humidity sensing was demonstrated with thermally-corrected output by an uncoated "reference" temperature sensor. Also presented were TPoS sensors for toluene and xylene, which are pollutants of great importance for indoor and outdoor air quality as well as health screenings. Silicon dual-mode resonators and oscillators for self-temperature sensing were also explored. Dual-mode thermometry exploits the inherent frequency-temperature dependence of silicon to accurately and locally measure device temperature, forming an essential building block of highly stable oscillators and sensors. Multi-axis piezo-on-Si kinetic energy harvesting (KEH) devices with integrated frequency-upconverting transducers were also introduced. Devices were micromachined on the same substrate as TPoS resonant sensors and have an individual volume in mm3, enabling applications in wireless autonomous sensor nodes. In remote locations where continuous operation may be required, TPoS energy harvesters can provide battery replacement or recharging alternatives that do not increase overall system size. Advisors/Committee Members: Ayazi, Farrokh (advisor), Brand, Oliver (committee member), Zhang, Ying (committee member), Allen, Mark G. (committee member), Bergin, Michael H. (committee member).

Subjects/Keywords: Piezoelectric micro-resonators; Environmental sensing; Silicon resonators; Gravimetric sensing

…mobile and portable systems. To validate the TPoS platform, gravimetric humidity sensing is… …miniaturized multi-sensing platform. 2.1 GRAVIMETRIC RESONATORS The model for mechanical resonance… …for gravimetric micro-sensing. 2.2.1 CAPACITIVE AND THERMAL ACTUATION Capacitive resonators… …4 TPOS GRAVIMETRIC RESONANT SENSORS… …30 4.2.1 4.2.2 Resonant Temperature and Humidity Sensing… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Fu, J. L. (2013). Micromachined piezoelectric-on-silicon platform for resonant sensing and energy harvesting. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52188

Chicago Manual of Style (16th Edition):

Fu, Jenna L. “Micromachined piezoelectric-on-silicon platform for resonant sensing and energy harvesting.” 2013. Doctoral Dissertation, Georgia Tech. Accessed October 16, 2019. http://hdl.handle.net/1853/52188.

MLA Handbook (7th Edition):

Fu, Jenna L. “Micromachined piezoelectric-on-silicon platform for resonant sensing and energy harvesting.” 2013. Web. 16 Oct 2019.

Vancouver:

Fu JL. Micromachined piezoelectric-on-silicon platform for resonant sensing and energy harvesting. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2019 Oct 16]. Available from: http://hdl.handle.net/1853/52188.

Council of Science Editors:

Fu JL. Micromachined piezoelectric-on-silicon platform for resonant sensing and energy harvesting. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/52188

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