流动电势是一种液体在外力作用下流过带电表面时产生的电场，在基础研究和工业生产中被广泛应用与表面zeta电势的测量。本论文发展了一种用于在微型通道中生成并检测流动电势的平台，对其构建方法以及实际应用进行了全面的研究和探讨。 / 我们构建的检测平台有三个主要组成部分：第一部分是两端植入有电极的微型通道，用于生成流动电势；第二部分是用于控制进液的注射泵；第三部分是用于读取电压信号的台式万用表。微型通道采用两种方法制备，分别生成聚二甲基硅氧烷与玻璃的杂化微型通道以及基于玻璃毛细管的微型通道。利用电脑程序控制，流动电势可在此平台中可自动产生和检测，并可运用Helmholtz-Smoluchowski公式转换成zeta电势。在本论文的第一部分中，该平台被用于研究不同的液体流动速度、电解质浓度以及溶液pH值对流动电势的影响，以及进行表面聚电解质组装的原位检测。 / 论文的第二部分探索了该平台在DNA无标记检测方面的应用。DNA的检测方法是在微型通道的内表面固定肽核酸（PNA）探针，利用PNA与DNA的杂化引入表面极性的变化，再通过流动电势的信号进行表征。研究结果表明，通过流动电势的测量，毛细管型微型通道中配对DNA的检测限可低至2nM并可区分配对DNA与CC错配DNA。在杂化型微型通道中，流动电势信号可对浓度范围在10- 200 nM的配对DNA进行定量响应，但检测的特异性较低。以上实验结果证明了这种基于流动电势测量的DNA传感器是一种低成本、原理简单、无需标记的DNA检测工具。 / 第三部分在原有的测量平台中加入了气动控制的微型蠕动泵以取代传统的注射泵用于在流动电势测量中控制液体的运动。我们制作的微型蠕动泵由三个顺序排列的正压驱动的主动阀门以及一个从动阀门组成，并可产生高达464 微升分钟的流速。采用该微型蠕动泵驱动液体流动可产生稳定的流动电势信号。实验结果初步证明了通过在微流芯片中植入微型蠕动泵可实现流动电势测量中电解质溶液的循环使用。 / This thesis describes the construction and application of a platform for streaming potential measurement in a microfluidic channel. Streaming potential is an electrokinetic phenomenon that produces electric field from pressure-driven liquid motion on a charged surface. The assessment of streaming potential is a widely-used method to determine the surface zeta-potential in both fundamental researches and industrial testings. / The platform we constructed was comprised of three parts: a disposable microfluidic channel with integrated microelectrodes, wherein the liquid flowed and generated streaming potential; a syringe pump to control the movement of liquid in the microfluidic channel; and a high-performance multimeter to monitor the potential signals. The microchannels were fabricated by two different approaches from glass and polydimethylsiloxane (PDMS), namely PDMS-glass hybrid microchannel and capillary-based microchannel respectively. The measurement was automated as both the syringe pump and the voltmeter were controlled by computer programs. The platform could determine zeta-potentials of microchannel surfaces from streaming potentials following the Helmholtz-Smoluchowski equation. We investigated the influence of the volumetric flow rate, electrolyte concentration and pH of the electrolyte solution on streaming potentials. The platform was demonstrated to be a simple, sensitive and reliable tool to measure streaming potentials and examine surface polarities. / We employed the platform to construct a label-free DNA sensor based on the hybridization of peptide nucleic acid (PNA) and DNA. The uncharged PNA probes were immobilized on the surface of microfluidic channels through routine chemical reactions. Upon forming hybrids with DNAs, more negative charges appeared on the PNA-coated micorchannel which were reflected in the shift of streaming potentials. We found that the DNA sensor using the capillary-based microchannel had a detection limit of 2 nM and could distinguish complementary DNAs from the DNA strands with a CC mismatch from original CG base pair. The sensor constructed by the hybrid microchannel could respond quantitatively to DNAs with a concentration of 10- 200 nM, whereas showed a lower specificity to the targeting DNAs. The streaming potential based DNA sensor enriches the tools for DNA diagnosis, and the sensor is inexpensive, straightforward, and requires no DNA labeling. / Finally, a pneumatic peristaltic micropump was fabricated to replace the bulky syringe pump to regulate the liquid motion in the platform. By combining together three consecutive active valves activated by positive pressure and one normally-closed passive valve, flow rate as high as 464 μL/min was generated and stable streaming potentials were obtained. The integration of the pneumatic micropump allowed recycling of liquids and fabrication of a more compact microchip for streaming potential measurement. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Yuefang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 80-84). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.iv / Table of Contents --- p.vi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Basic theory of streaming potential --- p.1 / Chapter 1.2 --- Streaming potential analyzer --- p.5 / Chapter 1.3 --- Applications of streaming potential phenomenon --- p.8 / Chapter 1.3.1 --- Generation and conversion of electrokinetic power --- p.8 / Chapter 1.3.2 --- Detection of pressure and flow velocity --- p.9 / Chapter 1.3.3 --- Quantification of zeta-potential --- p.10 / Chapter 1.4 --- Streaming potentials in nanofluidics and microfluidics --- p.11 / Chapter 1.5 --- Objective of the project --- p.13 / Chapter Chapter 2 --- Construction of the microfluidic platform for streaming potential measurement --- p.15 / Chapter 2.1 --- Introduction to microfluidic streaming potential analyzer --- p.15 / Chapter 2.2 --- Experimental --- p.17 / Chapter 2.2.1 --- Fabrication of the SP microchannels --- p.17 / Chapter 2.2.2 --- Streaming potential measurement --- p.18 / Chapter 2.2.3 --- Surface modification of the hybrid microchannels --- p.19 / Chapter 2.3 --- Results and discussions --- p.20 / Chapter 2.3.1 --- Zeta-potential determination --- p.20 / Chapter 2.3.2 --- Influence of electrolyte solution on streaming potentials --- p.24 / Chapter 2.3.3 --- In-situ characterization of layer-by-layer modification --- p.27 / Chapter 2.4 --- Conclusion --- p.28 / Chapter Chapter 3 --- A streaming potential-based DNA sensor --- p.30 / Chapter 3.1 --- Introduction to DNA sensors --- p.30 / Chapter 3.2 --- Experimental --- p.32 / Chapter 3.2.1 --- Immobilization of PNA probes on glass --- p.32 / Chapter 3.2.2 --- Hybridization experiment --- p.33 / Chapter 3.2.3 --- Characterization of the modified surface --- p.34 / Chapter 3.3 --- Results and Discussions --- p.35 / Chapter 3.3.1 --- PNA immobilization --- p.35 / Chapter 3.3.2 --- PNA/DNA hybridization --- p.39 / Chapter 3.3.3 --- Hybridization detection by streaming potentials --- p.41 / Chapter 3.3.4 --- PNA/DNA hybridization in PDMS-glass hybrid microchannel --- p.44 / Chapter 3.3.5 --- The capillary microchannel as DNA sensor --- p.49 / Chapter 3.4 --- Conclusion --- p.51 / Chapter Chapter 4 --- Application of pneumatic micropump in SP measurement --- p.53 / Chapter 4.1 --- Introduction to pneumatic micropump --- p.53 / Chapter 4.2 --- Experimental --- p.55 / Chapter 4.2.1 --- Fabrication of the pneumatic micropump --- p.55 / Chapter 4.2.2 --- Operation of the pneumatic micropumps --- p.58 / Chapter 4.2.3 --- Measurement of flow rate and streaming potential --- p.59 / Chapter 4.3 --- Results and discussion --- p.59 / Chapter 4.3.1 --- Design and evaluation of NPA micropumps --- p.59 / Chapter 4.3.2 --- Design and evaluation of the PPA micropumps --- p.64 / Chapter 4.3.3 --- Streaming potentials produced by micropump driven flow --- p.68 / Chapter 4.4 --- Conclusion --- p.71 / Chapter Chapter 5 --- Conclusions and perspectives --- p.72 / Chapter 5.1 --- Summary of the work --- p.72 / Chapter 5.2 --- Future perspectives --- p.73 / Chapter Appendix A --- Photolithography --- p.75 / Chapter Appendix B --- Pressure calibration --- p.77 / Reference --- p.80
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328132 |
| Date | January 2013 |
| Contributors | Li, Yuefang., Chinese University of Hong Kong Graduate School. Division of Chemistry. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (vii, 84 leaves) : ill. (some col.) |
| 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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