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Nanowire and Fiber Composite Electromechanical Sensor

Chen, Qian (2012) Nanowire and Fiber Composite Electromechanical Sensor. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Fiber or nanowire composites offer many benefits for piezoelectric sensor and actuator applications. Piezoelectric composite is comprised of piezoelectric ceramics lain in polymer matrix. The composite with the piezoelectric ceramics connected in one direction and the polymer in three directions is named as 1-3 composite. 1-3 composites are most ordinary used and the anisotropic alignment of PZT in the composite may substantially lower lateral piezoelectric coupling and increases the sensitivity of the transducer mechanically. Piezoelectric fiber composites are suitable for sensor applications, medical diagnostics and nondestructive testing.
Single crystal zinc-oxide nanowires were synthesized through a simple hydrothermal route and subsequently mixed with polyimide matrix to form ZnO nanocomposites. Superimposed a.c. and d.c. electric fields were applied to microscopically tailor the alignment of ZnO nanowires in polyimide matrix to form anisotropic nanocomposites. Piezoresistive property of ZnO nanocomposite was investigated for strain sensor application. A large gauge factor was obtained from the monotonic uniaxial stress-strain experiment for this nanocomposite and it is much higher than that of ordinary metal strain sensor. A low frequency fiber composite vibration sensor was fabricated and experimentally studied. The global parameters of the composite were substituted into lumped and distributed element constituent equations for piezoelectric unimorph to theoretically predict the sensitivity and effective frequency response range of the vibration sensor. An experiment was carried out to validate the result from the theoretical model. The output voltage per unit input displacement keeps stable in a wide frequency range with a suitable damping ratio. This PZT fiber composite sensor was also applied for soft material strain measurement and soft biomaterial surface morphology and elastic modulus characterization. From the theoretical evaluation and experiment result, this strain sensor is suitable for strain measurement with high sensitivity and high softness. A rectangular breathing sensor and an annular breathing sensor were fabricated for breathing rate and depth monitoring. Both sensors were tested under different physiological conditions and measurement results could be utilized for precaution and monitoring of breathing diseases. Both of them are excellent for monitoring breathing rate and depth and be nice choices for daily use and diagnose purpose.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Chen, Qianqic7@pitt.eduQIC7
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWang, Qing-Mingqiw4@pitt.eduQIW4
Committee MemberSlaughter, William S. wss@pitt.eduWSS
Committee MemberSmolinski, Patrickpatsmol@pitt.eduPATSMOL
Committee MemberTo, Albertalbertto@pitt.eduALBERTTO
Committee MemberMao, Zhi-Hongzhm4@pitt.eduZHM4
Date: 4 June 2012
Date Type: Publication
Defense Date: 16 March 2012
Approval Date: 4 June 2012
Submission Date: 19 March 2012
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 161
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Mechanical Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: PZT fiber, ZnO nanowire, composite, piezoelectric, piezoresistive, electromechanical, sensor
Date Deposited: 04 Jun 2012 19:01
Last Modified: 15 Nov 2016 13:56


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