Micro-electro-mechanical Systems (MEMS) technology has revolutionized the micro/nano world by making micro/nano devices feasible. These devices allow more exploration and understanding of the micro/nano world. In this dissertation, we will discuss the measurement of wall shear stress in an integrated microfluidic system built by MEMS technology. Specifically, carbon nanotubes (CNTs) were used as the sensing element for gas-flow shear stress measurement in this work. CNTs have already been proven to have an excellent sensing response to temperature, pressure, and alcohol vapour. Based on the thermal sensing response of CNTs, the sensor was designed to operate using convective heat transfer principles in fluid flow. Dielectrophretic manipulation was used to batch fabricate CNTs on a PMMA substrate. The CNT sensor was then integrated into a PMMA microchannel, which was fabricated by a rapid prototyping technique using moulding/hot-embossing processes. The sensor responded to impinging flow as well as gas-flow shear stress. The sensor activation power was found to be linearly related to the 1/3 exponential power of the wall shear stress. With the measurements of an array of sensors, the flow profile of a microchannel with various types of flow could be studied. Compared with the conventional polysilicon sensor, the CNT sensor has the advantage of small dimensions, i.e. a greater spatial resolution for fluidic measurements, and low power consumption, i.e. it consumes ∼1,000 times less power than polysilicon sensors. Therefore, CNT sensors have a great potential to serve as an alternative to silicon-based sensors. / Chow, Wing Yin Winnie. / Adviser: Wen J. Li. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3743. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 105-110). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344318 |
| Date | January 2008 |
| Contributors | Chow, Wing Yin Winnie., Chinese University of Hong Kong Graduate School. Division of Automation and Computer-Aided Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xiii, 110 leaves : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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