【作者】 杨胡坤；

【导师】 王扬； 姜洪源；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 微流控系统是20世纪90年代发展起来的一项高新技术,其主要以分析化学和分析生物化学为基础,以微机电加工技术为依托,以微管道网络为结构特征,是当前微全分析系统乃至芯片实验室发展的重点。在微流控系统中,微流体驱动技术是其中的一项关键技术,微流体驱动技术的好坏直接决定微流控系统的性能。尽管微流体驱动技术在过去的十余年得到了快速发展,但微流体驱动系统集成化和微流体驱动系统可靠性的提高仍然是微全分析系统的薄弱环节。交流电渗(AC electroosmosis, ACEO)是近几年发展起来的一项新技术,它以驱动电压低、芯片制作过程简单、容易与系统集成等优点而倍受学者青睐。目前国外对该技术研究还处于不断探索和完善阶段,而在国内关于该技术的研究成果报道甚少,因此展开对ACEO驱动微流体技术的研究具有重要的意义。本文从电渗驱动理论的基础出发,对直流电渗(DC electroosmosis, DCEO)和ACEO的驱动原理及双电层的产生的机理进行了详细的理论分析,揭示了其共同点和主要特征。经过设计毛细管DCEO微泵并进行实验,研究了DCEO流速与驱动电压、微通道结构的关系。针对ACEO中双电层的产生是由于电极极化产生的特征,从理论上推导了ACEO的流速公式。在研究非对称电极ACEO中,根据非对称电极ACEO驱动微流体实验现象,建立了非对称电极ACEO微流体驱动的物理模型。分析了非对称电极ACEO电场和流场特性及相互关系,研究了其边界条件的建立过程。对非对称电极ACEO驱动微流体流场进行了仿真,通过仿真与实验结果的对比分析,验证了理论研究的正确性。开展了行波电渗(Traveling wave electroosmosis,TWEO)驱动微流体的理论和实验研究。提出了一种新颖的用对称电极设计非对称电极ACEO驱动微流体芯片的方法,设计了驱动电路。阐述了粒子图像测速法在非对称电极ACEO和TWEO中的应用及实验数据处理方法,通过对比分析和实验研究,比较了两者芯片的加工过程,验证了在等效驱动电压的情况下,TWEO比ACEO驱动微流体具有更高的效率。以Gouy–Chapman–Stern双电层理论为基础,建立了TWEO驱动微流体非线性物理模型,经过线性变换,对TWEO驱动微流体进行了仿真分析,并对封闭通道内的Poiseuille流进行了分析。通过TWEO驱动微流体流场实验,验证了TWEO驱动微流体理论模型的正确性,获得了TWEO流场流线比ACEO流场流线更平坦结论。对TWEO驱动微流体流速影响因素进行实验及理论研究,研究了不同电导率溶液在TWEO中的容抗比例系数的确定方法和芯片电极的加工工艺,并对芯片电极材料、芯片基底材料、通道材料的选择进行了分析。对驱动不同电导率溶液的实验结果表明,电导率越小,出现最大速度峰值时的频率越小、速度峰值越大。并且通过改变电极参数可以达到改变电渗流流速及最大速度峰值时的频率的目的;同时,在低电势驱动下,在TWEO驱动微流体中,可以忽略电热效应、粒子介电泳运动等对实验测速的影响。综上所述,通过本文对电渗流微流体驱动基础理论和相关技术的研究,进一步证实了非对称电极ACEO驱动微流体具有输入信号电压低、芯片容易与系统集成等特点,比DCEO更具有工程应用的优越性。同时,理论及实验研究结果表明,TWEO比非对称电极ACEO在驱动微流体中更具有效率。因此,本论文的研究结果为电渗流技术的进一步深入研究和工程应用具有重要参考价值。本论文的研究得到了“高等学校学科创新引智计划项目(B07018)”的资助,同时受国家留学基金委“国家建设高水平大学公派研究生项目”资助(录取文号为留金出[2007]3020号)。更多还原

【Abstract】 Microfluidics system developed on 1990s is a technology that has emphasis on micro-total-analysis-system (μ-TAS) and lab on a chip based on chemical analysis and biological analysis. It is fabricated on MEMS technology and characterized by microchannel net. Its performance is determined by the key technology of microflow pumping. Despite of the rapid development of microflow pumping technology in the past more than ten years, there are still weakness which limit the application of the microfluidics system, such as the difficulties of systematic integration and the low reliability of the system. To overcome these shortcomings, AC elctroosmosis (ACEO) technology has been developed in recent years for its advantages such as low driving voltage, simple fabrication process and facility of integration with system. Currently, the research of ACEO is at developing stage abroad, while there are few publications have been found in China. Therefore, it is of great significance to research microflow pumping with ACEO.In the study, the theory and the mechanism, as well as the similarity and main features, of ACEO and DC electroosmotic (DCEO) were analyzed. With the design and the test of capillary DCEO pump, the driving voltages and microchannel structures impacting on pumping velocity of DCEO were investigated. In ACEO, the double electric layer is caused by electrode polarization. The velocity formula on ACEO was deduced from the comparison of the mechanism of ACEO and DCEO.In the study of asymmetry ACEO, the physical model of electric field and flow field was proposed based on ACEO pumping microflow experimental phenomenon. The electric and velocity fields with their boundary conditions were analyzed in the simulation. By comparing experimental and simulated results of velocity field of ACEO microflow pumping simulation, the theoretical model was verified.A new idea for the research of traveling wave electromosis (TWEO), that is, a new driving circuit for the chip used in a symmetry electrode array, was presented. The applications of particle image velocity (PIV) method for the measurement of velocity of moving particles and the method of image processing in ACEO and TWEO were discussed. According to the experimental and practical uses, the fabrication processes for ACEO and TWEO chip were compared. Under equivalent driving voltages, the experiments for ACEO and TWEO were studied. The results shows that compared with ACEO, TWEO was more efficient in driving particles. The nonlinear model of voltage distribution for TWEO pumping microflow was presented based on Gouy-Chapman-Stern double electric layer theory. With linear transform, TWEO was simulated. The Poiseuille flow in a closed microchannel was analyzed. The theoretical model of TWEO pumping microflow was verified experimentally. The simulated results show that the streamline of TWEO is smoother than that of ACEO.The factors that influencing characteristics of TWEO microflow pumping were explored experimentally and theoretically. The method for the determination of capacitance ratio coefficients in TWEO with different conductivity of solutions was proposed. Furthermore, the chip electrode fabrication process was shown. The selections of material for chip electrode, substrate and channel were discussed. The experimental results of pumping different conductivity solution show that for lower conductivity electrolyte, the bigger the peak velocity value is, the smaller the frequency for peak velocity is. It is concluded from experimental and theoretical analysis that the variation of structural parameters of electrode may change the electroosmosis velocity and the frequency on peak velocity value. For a low voltage, the effect of electrothermal, particle dielectrophoresis motion and other several factors on the measurement of flow velocity in TWEO microflow pumping can be ignored.On the above discussion, with the basis theory and technology of electroosmosis microflow pumping in this research, ACEO application in engineering has more advantages than DCEO, such as low voltage, facility of integration. Theoretical and experimental research results show that TWEO is more efficiency than ACEO. The experimental and theoretical results are beneficial to the practical application of electroosmosis microflow pumping.The study is sponsored by the Chinese 111 project (Grant Number: B07018) and China Scholarship council“National Project for Sending Graduated Students to Build High Level Universities”(Grant Number: [2007]3020).更多还原