【作者】 杨大勇；

【导师】 刘莹；

【作者基本信息】 南昌大学 ， 机械电子工程， 2009， 博士

【摘要】 微流控芯片是一种新型的微全分析系统,可用于分析化学和生物医学等领域的分析和检测,具有试剂用量少、分析速度快和成本低等优点。本文在对国内外微流控芯片发展概况和存在问题进行深入分析研究的基础上,针对微流控芯片在加工和应用中存在的表面效应等问题,采用理论分析、数值模拟和实验研究相结合的方法,对微流控芯片中的电渗流输运规律进行了系统的研究。本文完成的主要研究工作和创新成果如下:1、研究了微流控中存在的动电现象和微流体的常用驱动与控制机理,基于多物理场耦合特征,提出了电动微流体的总体研究方案,分析了微流控芯片中的一般数学模型,采用有限元方法(FEM)离散控制方程,推导了双电层电场Poisson-Boltzmann方程、外加应用电场Laplace方程及电渗流场Navier-Stokes方程等的求解步骤,为全文的理论分析和数值模拟确定了具体的研究路线。2、在光滑微通道电渗流(EOF)特性的基础上,采用基于FEM的COMSOL软件,模拟了具有矩形、三角形、正弦和准分形粗糙表面的微通道EOF,对微通道近壁区、主流区分别进行了分析。研究表明,在近壁区,粗糙表面会导致EOF速度出现局部极大值;在主流区,当粗糙度在微米范围以内时,主流EOF速度基本保持不变;整体范围内,EOF速度会随着粗糙度的增大而非线性降低,当粗糙元高度接近0.3倍EDL厚度时,EOF速度受到粗糙度影响最大。该结果揭示了粗糙结构对EOF的影响机理,对于微流动的摩擦研究具有指导意义。3、对疏水和亲水表面微通道内的EOF进行了瞬态和稳态数值模拟,研究表明,亲水表面与疏水表面光滑微通道相同,EOF的稳态时间尺度在毫秒量级,其大小与微通道高度的平方成正比,EOF速度与电场强度成正比;随着溶液浓度的增大,疏水表面较亲水表面微通道EOF速度增大明显。该结果对于提高疏水表面微通道内EOF控制精度有参考价值。4、对光滑和粗糙表面的3D微流控芯片中的样品传输、进样和分离过程进行了系统级的数值模拟,结果显示表面粗糙度使样品区带增宽,出现峰面“拖尾”现象,提出可以通过调节微通道内的外加电压场强分布加以解决。该结果对于提高粗糙表面微流控芯片中样品分析的效率和精度有重要意义。5、以聚甲基丙烯酸甲酯(PMMA)为材料,设计和制作了两种PMMA微流控芯片,并测量了其表面形貌参数;基于电流监测法原理,设计并组建了多通道EOF检测实验系统,采用虚拟仪器软件LabVIEW开发了检测平台;在此基础上,完成了PMMA微流控芯片内流体流动的测试。本文的理论分析、数值模拟和实验结果吻合良好,对于微流控芯片的基础研究、设计开发及其应用具有重要的理论意义和现实意义。更多还原

【Abstract】 Microfluidic Chip (MFC) is a novel kind of micro total analytical system. It can enhance the performance of chemical analysis with respect to smaller amounts of samples, higher analysis speed, better sensitivity and low cost, which can be used to in the fields of the analytical chemistry, biomedicine, etc. In this thesis, on the basis of deep analyzing and studying domestic and foreign development conditions and existing problems of MFC, aiming at the problems in the process of the manufacturing and application, the transporting rules of fluid in MFC were studied systematically, using the methods of theoretical analysis, numerical simulation and experimental instruments. The main innovative jobs are as followed:The electrokinetic phenomena, as well as the driving and controlling mechanism of the microfluid are studied firstly. The total project of electrokinetic microfluid was summarized based on its multiphysics field coupling characters, and the general mathematical models of MFC were also analyzed. Based on the finite element method (FEM), the Poisson-Boltzmann equation of electric double layer electric field, the Laplace equation of external electric field and the Navier-Stokes equation of electroosmotic flow (EOF) field were discretized, which form the detailed research scheme of the theoretical analysis and numerical simulation.On the basis of the EOF characteristics in smooth microchannel, the EOF was modeled in rough microchannel with rectangle, triangle, sinusoidal and quasi-fractal roughness element, using the COMSOL Multiphysics based on the FEM, which were all divided into the near-wall and bulk flow area. The simulation results indicate that there is a local max value of EOF velocity in the near-wall area of the rough microchannel and the bulk flow EOF velocity almost keep invariable while the roughness is in the scope of the micrometers. In the whole channel, the average EOF velocity decreased nonlinearly with the increasing of the roughness, which decrease quickly when the roughness element height is 0.3 times of the EDL thickness. The results show the mechanisms of the rough element to EOF, which can guide the friction research of the microflow.The transient and the steady state of the EOF were modeled in hydrophobic and hydrophilic microchannel. The results show that the transient characteristics of EOF are similar in hydrophobic and hydrophilic microchannels, the steady time of EOF is proportional to the square of microchannel scale, and the magnitude is microsecond. EOF velocity in hydrophobic microchannel is proportional to the electric strength and independent of the channel height, and decreases slowly with the ionic concentration, which is lower than that in hydrophilic microchannel. The results can provide the reference for the EOF control in hydrophobic microchannel.The microflow processes, such as sample transport and separation in smooth and rough 3D MFC, were modeled in the level of system. The results indicate that the surface roughness can enlarge the sample zone and there is a "delay phenomenon" in the profile of the microflow, which can be eliminated by adjusting the applied electric strength in microchannels. The results can improve the separate efficiency and accuracy of sample in rough microfluidic chips.Two kinds of polymethyl methacrylate (PMMA) microfluidic chips were planed and manufactured. The surface parameters were also tested. Based on the current monitoring method, the multi-channel EOF experimental systems was designed and build up and the virtual instrument LabVIEW software was also used to develop the data acquisition human machine interface. The EOF in PMMA microfluidic chips was achieved on the experiment system at last.The results of the theoretical analysis, numerical simulation and experiment coincide very well, which have important theoretical significance and practical values to the fundamental research, development and application of MFC.更多还原