This thesis is missing page i, all other copies are missing this page as well. - Digitization Centre / Emergence of efficient cooling techniques has been a crucial factor in development of faster and more powerful electronic equipment and ICs. One of the key obstacles towards further miniaturization is efficient heat removal from regions of high temperature to maintain continued operation of these devices below their maximum operating range. Recently, a significant amount of research has been directed to develop liquid based cooling techniques. For example, microchannel heatsinks have been designed to remove up to 1 kW/cm2. Developing microscale actuators that provide sufficient pressure head is essential for integrating these microscale cooling schemes with the electronic devices. Different techniques can be used to pump fluid in the microscale such as electroosmotic, magnetohydrodynamic, and electrohydrodynamic (EHD) pumping. Among these technologies, EHD pumps are particularly promising for microfluidic devices because they use no moving parts, and uses very small power and has low cost and maintenance requirements. This work presents the development and test of EHD micropumps with different electrode configurations. Four different electrode configurations: (1) planar symmetric electrodes, (2) planar asymmetric electrodes, (3) 3-D symmetric electrodes, and (4) 3-D asymmetric electrodes were investigated. In addition, the effect of different design specifications, such as the inter-electrode spacing and spanwise spacing of the micropillars were investigated. The electrodes were fabricated using a two mask process. First, a thin layer of chromium was deposited on glass as a seed layer for gold electrodes. Positive photoresist (AZ P4620) was patterned to form the mould for the micropillar electrodes. Nickel was electroplated to fill the mold. Subsequently, a Cr/Au layer was patterned to devise the electrode base connector and pads. The microfluidic channels were fabricated by casting polydimethylsiloxane (PDMS) on top of an SU-8 100 (MicroChem Corp.) mould which was patterned to delineate the microchannel structure. The PDMS microchannel was integrated on the electrode base by plasma oxidizing the PDMS and glass wafer, and sealing the connection with liquid PDMS. The pump performance was experimentally determined with Methoxynonafluorobutane (HFE-7100) as the working fluid. All of the micropumps were tested under a no net flow condition to find the maximum pressure generation. The micropumps with planar and asymmetric planar electrode configurations were also tested for maximum flow rate under no imposed back pressure. The results show that the micropumps with the 3D asymmetric electrode design generated a higher pressure head compared to the other micropumps with identical inter electrode spacing under no flow conditions. The micropumps with planar asymmetric design had a higher performance compared to the micropumps with planar asymmetric electric under both no flow condition and no back pressure condition. A maximum pressure head of 2240 Pa was generated at an applied voltage of 900 V by the micropump with 3D asymmetric electrode design. A maximum flow rate of 0.127 mL/min was achieved by the micropump with planar asymmetric electrode configurations. This is five times higher than the maximum flow rate generated by the micropump with the planar symmetric electrode design. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24389 |
| Date | January 2007 |
| Creators | Kazemi, Pouya |
| Contributors | Ching, C. Y., Selvaganapathy, P., Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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