基于微流控捕获技术的孤立颗粒体散射函数研究

发布时间：2019-03-09 18:08

【摘要】：颗粒的光学体散射函数特性是颗粒的一项重要的物理学特性。传统的颗粒体散射函数研究主要建立在使用颗粒群样本间接测量的基础上,现有的孤立颗粒体散射函数直接测量方法存在样本适应性差和易受环境因素干扰等缺点。因此,设计一种稳定、可靠、快速、环境依赖少的孤立颗粒体散射函数测量系统具有十分重要的价值。本论文,从孤立颗粒样本捕获和体散射函数测量两个方向出发,结合微流控芯片技术,提出了基于流体力颗粒捕获微流芯片的孤立颗粒体散射函数测量方法,解决了孤立颗粒体散射测量的核心问题。通过综合运用流体力学方法与有限元分析工具,设计并制备具有自调节能力的孤立颗粒捕获微流控芯片；根据孤立颗粒光散射的特点,设计了基于空间滤波器和PMT光电探测器的散射光接收装置；基于各模块设计成果,完成了孤立颗粒体散射函数测量系统,通过对不同粒径颗粒的实际测量和分析,验证了该系统用于孤立颗粒体散射函数研究的有效性和探测能力。本论文阐述了微流控芯片内部流道中的流场分布特点,通过建立流阻等效模型,运用Matlab对流道结构参数与流场分布特性关系进行了综合计算,提出了一种不仅可同时达到高捕获效率和高捕获准确率,而且利用捕获微粒自身对流体分布进行自动反馈调节的微流道结构。运用有限元流体计算工具,对前述结构进行三维仿真研究,并进一步对影响捕获效果的流场局部特征进行优化。在此基础上设计并制备了具有高光学透过率的孤立颗粒捕获芯片。为实现孤立颗粒散射光的有效探测,通过原理分析、理论计算、数值仿真和综合对比,设计并搭建了一套基于空间滤波器和PMT光电探测器的角度扫描式大动态范围散射光测量模块,并实验验证了系统实际视场和大光强动态范围下的线性度。基于理论分析与上述孤立颗粒捕获模块、散射光测量模块的研究成果,研制了一套孤立颗粒体散射函数测量系统。通过消除了有机溶液吸胀、环境温度波动和层流边界对折射率匹配的影响,提高了光学匹配效果。通过空间精密对准,对实际捕获的孤立聚苯乙烯颗粒的大角度范围内的体散射函数进行实际测量。多次重复测量20.42μm颗粒在20至1620之间的散射光分布在光强变化约1×106范围内的波动中心值约为20%-25%。直径分别为23μm,23.75μm,31μm的聚苯乙烯标准颗粒样品的实验结果与Mie散射理论曲线趋势上符合良好。实验数据和理论曲线中20°至55°区间内数据进行曲线拟合和参数分析,相同粒径颗粒的理论与实验拟合参数差别不大于8.6%；不同粒径颗粒的拟合参数间差异明显。通过对颗粒体散射函数的实际测量与分析,证明本方法在定性和定量角度均与理论曲线符合较好,是一种快速、有效且富有潜力的孤立颗粒体散射测量方法。
[Abstract]:The optical scattering function of particles is an important physical property of particles. The traditional research on particle scattering function is mainly based on the indirect measurement of particle group samples. The existing methods for direct measurement of isolated particle scattering function have some disadvantages such as poor sample adaptability and easy to be disturbed by environmental factors. Therefore, it is very important to design an isolated particle scattering function measurement system which is stable, reliable, fast and less dependent on the environment. In this thesis, based on the technique of microfluidic chip, an isolated particle scattering function measurement method based on fluid particle capture microfluidic chip is proposed, which is based on the capture of isolated particle samples and the measurement of volume scattering function, and the microfluidic chip technology is used to measure the scattering function of isolated particles. The core problem of scattering measurement of isolated particles is solved. An isolated particle capture microfluidic chip with self-adjusting ability was designed and fabricated by using fluid mechanics method and finite element analysis tools. According to the characteristics of isolated particle light scattering, a scattering light receiving device based on spatial filter and PMT photodetector is designed. Based on the design results of each module, an isolated particle scattering function measurement system is completed. Through the actual measurement and analysis of different particle sizes, the validity and detection ability of the system used in the study of scattering function of isolated particles are verified. In this paper, the characteristics of flow field distribution in the internal channel of microfluidic chip are described. By establishing the equivalent model of flow resistance, the relationship between the structural parameters of the channel and the distribution characteristics of the flow field is comprehensively calculated by using Matlab. This paper presents a micro-channel structure which not only can achieve high capture efficiency and high capture accuracy at the same time, but also uses the captured particles to adjust the fluid distribution automatically. The three-dimensional simulation of the above-mentioned structure is carried out by using the finite element fluid calculation tool, and the local characteristics of the flow field affecting the capture effect are further optimized. On this basis, an isolated particle capture chip with high optical transmittance was designed and fabricated. In order to realize the effective detection of isolated particle scattering light, through the principle analysis, theoretical calculation, numerical simulation and comprehensive comparison, A set of angular scanning large dynamic range scattering light measurement module based on spatial filter and PMT photodetector is designed and built. The linearity of the system in real field of view and large dynamic range of light intensity is verified by experiments. Based on the theoretical analysis, above-mentioned solitary particle capture module and scattering light measurement module, a set of scattering function measurement system for isolated particles is developed. The optical matching effect is improved by eliminating the effects of organic solution imbibition, ambient temperature fluctuation and laminar boundary on refractive index matching. The volume scattering function in the wide angle range of the isolated polystyrene particles captured in practice is measured by space precision alignment. The scattering light distribution of 20.42 渭 m particles in the range of 20 to 1620 is measured repeatedly. The center value of the scattering light distribution in the range of 1 脳 10 ~ 6 is about 20% ~ 25%. The experimental results of polystyrene standard particles with diameters of 23 渭 m, 23. 75 渭 m and 31 渭 m are in good agreement with the theoretical curve of Mie scattering. The curve fitting and parameter analysis between the experimental data and the theoretical data in the range of 20 掳to 55 掳show that the theoretical and experimental fitting parameters of the same particle size are less than 8.6%, and the fitting parameters of different particle sizes are obviously different. Through the actual measurement and analysis of particle scattering function, it is proved that this method is a fast, effective and potential method for measuring the scattering of isolated particles from both qualitative and quantitative angles in good agreement with the theoretical curve.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN492

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