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ACOUSTIC EJECTOR EMPLOYING LENS WITH AIR-REFLECTORS AND
PIEZOELECTRICALLY ACTUATED TUNABLE CAPACITOR
by
Chuang-Yuan Lee
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ENGINEERING)
August 2007
Copyright 2007 Chuang-Yuan Lee
Object Description
| Title | Acoustic ejector employing lens with air-reflectors and piezoelectrically actuated tunable capacitor |
| Author | Lee, Chuang-Yuan |
| Author email | chuangyl@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-06-20 |
| Date submitted | 2007 |
| Restricted until | Unrestricted |
| Date published | 2007-07-23 |
| Advisor (committee chair) | Kim, Eun Sok |
| Advisor (committee member) |
Katsouleas, Thomas Meng, Ellis |
| Abstract | This thesis presents microfluidic and radio-frequency (RF) microelectromechanical systems (MEMS) based on acoustic ejectors employing lens with air-reflectors (LWAR) and piezoelectrically actuated tunable capacitors, respectively.; For microfluidic MEMS, a new acoustic ejector with LWAR has been developed. This ejector requires no nozzle, nor heat for actuation, but uses LWAR to effectively focus acoustic waves for droplet ejection. LWAR utilizes the innate acoustic impedance mismatch between solid and gas, and has wide tolerance for its lens geometry. Ejections by the LWAR ejectors are demonstrated to be stable and repeatable. The acoustic ejectors are further integrated with reservoirs and channels for automatic liquid delivery, and continuous ejections have been attained without any frequency tuning.; Based on the LWAR ejectors, ejections of micron-sized droplets are attained through harmonic operations, and ejections in directional angles are realized through electrode pattern designs. Both harmonic operations and directional ejections are demonstrated to be stable and reproducible. Also the LWAR ejector is shown to dispense oil with large viscosity without any difficulty. With the mentioned abilities, this droplet-on-demand acoustic ejector has been successfully utilized for various biochemical applications, including DNA synthesis, droplet coalescence in air, and microreactions with oil encapsulation.; For RF MEMS, the first MEMS piezoelectric tunable capacitors employing ZnO actuation have been developed. Three different types of ZnO-actuated tunable capacitors are fabricated with surface and bulk micromachining techniques. The piezoelectric deflection is demonstrated to be linear and bi-directional, and the frequency response is fast and immune to environmental vibrations.; With the design of a bulk-micromachined mass structure driven by a ZnO unimorph, a 2,100% continuous capacitance tuning range (from 0.46 pF to 10.02 pF) is achieved with applied voltages from -35 V to +25 V. This is the highest tuning ratio ever reported for parallel-plate tunable capacitors. Another bridge-type surfacemicromachined tunable capacitor with a much smaller dimension is fabricated on a single chip without any bonding. Through the implementation of a simply-supported bridge structure driven by two ZnO-actuated cantilevers, 1400% continuous tuning from 0.13 pF to 1.82 pF is demonstrated without large stress developed in the bridge. |
| Keyword | ejector; tunable capacitor |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m639 |
| Rights | Lee, Chuang-Yuan |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Lee-20070723 |
| Archival file | uscthesesreloadpub_Volume48/etd-Lee-20070723.pdf |
Description
| Title | Page 1 |
| Full text | ACOUSTIC EJECTOR EMPLOYING LENS WITH AIR-REFLECTORS AND PIEZOELECTRICALLY ACTUATED TUNABLE CAPACITOR by Chuang-Yuan Lee A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (ENGINEERING) August 2007 Copyright 2007 Chuang-Yuan Lee |
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