Ryu, KyungJoo
(2008)
MICRO PUMPING AND SEPARATING/COLLECTING PARTICLES USING OSCILLATING BUBBLES.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
When a gaseous bubble in liquid is excited by acoustic waves, it oscillates in harmony with the wave and generates strong vortical flows around it, so-called cavitational microstreaming. In this thesis, the microstreaming phenomenon is investigated in development of two microfluidic devices: micropump and microparticle separator. In the micropump, the key idea is to vertically place a capillary tube above the oscillating bubble to collect the upward microstreaming flow into the tube. When the bubble is excited at its resonance frequency, it oscillates with surface undulations (surface wave mode) and pumps water through the tube. The performance of micro pumping is experimentally studied in various conditions in terms of the generated flow rate and pressure. The maximum flow rate and generated pressure are measured at ~0.7 ¥ìl and 1.8 Pa, indicating that the present pump falls into high-flow-rate and low-pressure type pumps. The present pump runs without physical connections or electric wiring to bubbles, implicating potential applications of implantable micropumps. The microparticle separator utilizes the recently-discovered phenomenon that the oscillating bubble attracts and captures large neighboring objects, not small objects (< 20 ¥ìm). This capturing principle is evaluated in three different microfluidic configurations: mini- and micro-channels and microchamber. Single or multiple microbubbles are deposited on Teflon-patterned spots or microcavities in the channel and oscillated by an acoustic wave. When a mixture solution with 80- and 2-¥ìm particles is injected into the channels, only the 80-¥ìm particles are captured near the oscillating bubbles while the 2-¥ìm particles pass the bubbles without being captured. By simply turning off the acoustic wave, the captured 80-¥ìm particles are easily released. A similar capturing (separating) operation is achieved in the microchamber. Since the filled water in the microchamber is quiescent, oscillating bubbles need to move in the chamber to selectively capture 80-¥ìm particles suspended in the chamber. 2-D movements of oscillating bubbles are achieved by sequentially activating arrayed square electrodes on the chamber bottom surface, so-called electrowetting-on-dielectric (EWOD). When the bubble is simultaneously actuated by EWOD and acoustic excitation, it captures and carries 80-¥ìm particles, not 2-¥ìm particles.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
8 September 2008 |
| Date Type: |
Completion |
| Defense Date: |
10 July 2008 |
| Approval Date: |
8 September 2008 |
| Submission Date: |
28 July 2008 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering |
| Degree: |
MSME - Master of Science in Mechanical Engineering |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
MEMS; microfabrication; microfluidics |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-07282008-113542/, etd-07282008-113542 |
| Date Deposited: |
10 Nov 2011 19:54 |
| Last Modified: |
15 Nov 2016 13:47 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/8684 |
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