微通道内液滴生成与混合理论方法与实验研究

发布时间：2018-01-31 01:36

本文关键词： 微流控芯片微液滴混沌对流快速混合迪恩涡旋转扰动　出处：《河北工业大学》2016年博士论文　论文类型：学位论文

【摘要】：随着微机电系统的迅速发展,流体控制器件的微型化、集成化成为重要的研究方向之一。微流控芯片主要应用于生命科学、分析化学等领域。在这些领域中反应是十分重要的单元操作,充分的混合是实现微流控器件功能的重要条件。快速均一混合对于化学合成、生化分析、药物输送、核酸测序或合成等领域中的微流控系统具有重要的意义。微流体以层流或低雷诺数为主要流体特征,分层不掺混的流动造成了混合困难。微混合器和微混合技术的引入给微流体快速高效混合带来了突破性的发展。尤其是,微液滴混合技术以分散的液滴单元作为密闭的微反应器,具有快速、高效、易控制和易集成的特点,成为微流体混合技术的研究重点之一。本文采用数值模拟和实验研究相结合的方法,研究了微流体内层流混合困难的问题,提出了基于正弦变截面微通道的液滴快速均一混合方法。利用正弦变截面微通道的几何结构实现了不同维度涡系间的共同作用,从而强化流体通道内的扰动达到充分混合;利用自主设计、封装的聚二甲基硅氧烷(polydimethylsiloxane,PDMS)微混合器芯片,在微米尺度范围内开展液滴生成与混合实验研究。实验结果与仿真分析结果吻合较好,进一步验证了高效微混合器开发的可行性。主要研究以下几方面内容:(1)建立T型微通道二维几何模型,对两相流流场(不可压缩流体的NaiverStokes方程)和温度场(能量守恒方程)进行耦合求解,揭示了T型通道内的液滴生成机理及连续相流速、连续相粘度对液滴生成的影响规律。(2)建立了微混合过程中的浓度传输方程,揭示了扩散混合和对流混合的机理,提出了增强微混合的有效途径。研究表明,混沌对流混合是微尺度下增强相溶两相流体混合效果的最佳方法。同时建立了微混合器性能的定量评价指标,为后续混合性能的定量评价奠定基础。(3)在液滴生成数学模型的基础上,将二维通道模型中的对流扩散方程与两相流水平集方程进行耦合求解,得到了正弦变截面微通道中液滴内混合组分浓度变化规律。在正弦变截面微通道中,利用液滴生成时通道入口处的旋转扰动作用、变截面效应和不对称循环流三者的共同作用,显著增强了液滴内的混合效果。在20s-30s内,液滴内的混合指数即可达到0.9以上,实现了快速高效混合。(4)分析了基于正弦变截面微通道中连续相流速、液滴的长度、正弦通道波长与振幅的比值、波长与振幅的乘积等结构参数对液滴内混合指数的影响,揭示了其对液滴混合效果的影响规律。(5)基于自主设计加工的PDMS微混合器芯片,利用T型通道法在微混合器内生成均一稳定的液滴,并利用液滴成功包裹酵母菌。在此基础上开展了基于微液滴的快速混合实验研究。结合仿真分析结果,分析了入口形式、两相流率比、液滴尺寸、振幅与波长的乘积、波数对混合效率的影响。实验结果与仿真分析结果吻合较好,验证了基于微液滴的快速混合机理和仿真模型的有效性。通过对微通道中液滴内相溶两流体快速均一混合的理论分析、仿真研究和大量的实验验证,利用自主设计、封装的微混合器芯片,基于液滴的快速微混合技术,通过液滴的形变、液滴内的不对称循环流及入口旋转扰动,在几十秒内可实现液滴内不同流体的快速均一混合。
[Abstract]:With the rapid development of MEMS, micro fluid control devices, integration has become one of the important research direction. The microfluidic chip mainly applied in life science, analytical chemistry and other fields. The reaction in these areas is a very important unit operation, sufficient mixing is an important condition to realize the function of micro fluidic devices. Fast uniform mixing for chemical synthesis, biochemical analysis, drug delivery, plays an important role in microfluidic system or synthetic nucleic acid sequencing and other fields. The micro fluid in a laminar flow or low Reynolds number as the main characteristics of fluid, flow stratified mixing caused difficulties. Hybrid micro mixer and micro hybrid technology is introduced to the micro fluid fast efficient mixing brings a breakthrough in the development. Especially, the droplet droplet unit mixing technology to disperse as closed micro reactor, with fast, efficient, easy to control and easy to set The characteristics, becomes one of the focuses of micro fluid mixing technology. This paper uses the method of numerical simulation combined with experimental study, to study the micro flow in laminar mixing difficult problem, proposed the droplet fast homogeneous method of sine tapered micro channel based on geometric structure. Using sinusoidal variable cross section micro channel to achieve the interaction between the different dimensions of the vortex, thereby strengthening the fluid channel disturbance to achieve full mixing; using independent design, package two polydimethylsiloxane (polydimethylsiloxane, PDMS) micro mixer chip, carry out experimental study on droplet formation and mixing in the micro meter scale. The experimental results and the simulation results are in good agreement, further to verify the feasibility of micro mixer development. The main research contents as following: (1) the establishment of T type micro channel two-dimensional geometry model of two-phase flow (not The NaiverStokes equation of compressible fluid) and temperature (energy conservation) coupling droplet formation mechanism of type T in the channel and reveals the flow velocity of the continuous phase, influence of continuous phase viscosity on the droplet generation. (2) the establishment of a micro concentration transmission during the mixing process, diffusion and convection mixed reveal the mechanism, put forward an effective way to enhance the micro mixing. The results show that chaotic convective mixing is the best way to dissolve the effect of two-phase enhanced micro scale. At the same time established a quantitative evaluation index of Micromixer performance, lay the foundation for subsequent quantitative evaluation of the mixing performance. (3) generated based on mathematical model in the droplet, the two-dimensional convection diffusion equation in channel model and two-phase set equation solved by coupling the horizontal flow, the sinusoidal variable cross section micro channel drops in the mixed component concentration variation in the positive. String variable section in the micro channel, by rotating the disturbance of droplet formation at the entrance channel, the interaction of variable cross-section effect and asymmetric circulation flow, enhance the mixing effect of droplets. In 20s-30s, you can drop in the mixing index reached more than 0.9, to achieve fast and efficient hybrid (. 4) based on the analysis of sinusoidal variable cross-section in the micro channel continuous phase velocity, droplet length, ratio of length and amplitude of the sinusoidal channel, wavelength and amplitude effect of product structure parameters on the droplet mixing index, reveals its influence to the droplet mixing effect. (5) self design and processing the PDMS chip based on Micro mixer, using T type channel method in micro mixer to generate droplets of uniform and stable, and the droplet successfully wrapped yeast. On the basis of experiment were carried out to study the rapid mixing of water droplets. Based on the analysis combined with simulation Fruit, analysis of the entrance, two phase flow, droplet size, product of amplitude and wavelength, wavenumber effect on mixing efficiency. The experimental results and the simulation results are in good agreement, to verify the effectiveness of the rapid mixing mechanism of micro droplet and based on simulation model. Based on the micro channel inside the droplet phase theoretical analysis of mixed two fluid fast uniform, simulation study and experimental verification, the use of independent design, micro mixer chip package, droplet rapid mixing technology based on the deformation of the droplet droplet in the asymmetric circulation and entrance rotational perturbations in dozens of seconds can achieve rapid mixing of different fluids homogenization the droplet.

【学位授予单位】：河北工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH-39

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