倏逝波光阱中多微球动力学理论和实验研究

发布时间：2018-07-10 17:44

本文选题：双光束光阱 + 四光束光阱　；参考：《国防科学技术大学》2016年博士论文

【摘要】：光与分散体系中分散相微粒的相互作用包含着能量和动量的传递。光阱技术可以限制微粒运动的特性使得人们可以方便的观测分散体系中单个微粒的动力学过程,这对于研究微粒的个体行为和彼此间的相互作用是非常有用的。例如光阱中存在多微球的情况,其中每个微球不仅受到来自背景光场的力作用,还受到来自其他微球散射光场和流体运动的影响。在适当的条件下,多微球可以集聚形成各种结构,即光学结合(Opitcal binding)现象。尽管光阱中单微粒的力学特性已经被广泛研究,但人们往往容易忽视多微粒散射光的力学效应,因而对多微球动力学的定量研究显得比较粗糙;同时倏逝波光阱作为二维光阱,为光学结合现象提供了天然的载体,尚没有对紧密结构中微球行为特性的定量研究。对这些现象的观测和研究,可以帮助人们更加全面的认识光力作用和拓展新的应用。基于这些需求,本文观测了倏逝波光阱中多微球在光力作用下集聚形成小间隔的一维和二维结构的实验现象,利用微球的位置波动定量的分析了单体微球和一维微球链的动力学特性。主要研究工作包括以下几个方面:1.单微球布朗动力学仿真。比较了常用的光阱刚度标定方法,指出均方位移法和玻尔兹曼法都不需要微球在流体中的粘度信息,这种特性有助于近平面倏逝波光阱刚度的标定。利用蒙特卡洛法和有限元法分别通过位置和速度迭代方式仿真了流体中单微球在受限布朗运动影响下的位置波动,比较了它们的特点,介绍了速度相关记忆时间和位置相关记忆时间的概念。通过仿真结果求解刚度发现二者的误差相当,但位置迭代方式计算时间显著缩短了3~4个量级。在仿真中发现当光阱中两个正交方向上刚度差异较大时,二维坐标系的选取可以对微球位置波动相关函数造成显著的影响。最后仿真了微球在外力矩作用下转动并受到布朗运动影响的位置波动,分析了三种情况下微球位置波动相关函数的特性,即转动位移占主要因素的情况、布朗位移占主要因素的情况和介于二者之间的情况,这种相关函数的分析提供了一种测量微球转动信息的方法。2.倏逝波光阱系统。搭建了双光束倏逝波光阱系统,观测到直径1umSiO2的微球形成一维链式结构的实验现象;搭建了四光束倏逝波光阱系统,观测到直径1umSiO2的微球形成二维结构的实验现象。3.多微球位置同时探测算法的实现。描述了显微镜物镜衍射成像的特点,仿真了设定信噪比下点源在图像传感器中所成的数字图像。比较了单微球位置探测常用的图像分析算法,根据观察的微球链的运动特性,改进了现有的极值中心法,在取得同等探测精度的前提下大幅缩短了探测时间,为后续实验中多微球位置的探测奠定了基础。4.一维结构中单体微球动力学特性的研究。在双光束倏逝波光阱中,直径1um的SiO2微球在光力作用下形成间隔紧密的一维微球链。在得到微球的位置波动后,分析了不同条件下微球平均间隔的差异;将每个微球看作处于各自的势阱中,这些势阱的刚度可以通过球-弹簧模型中各微球间连接弹簧的弹性系数来获得。在不同条件下分别计算了链式结构中连接弹簧的弹性系数,并首次从实验中定量地确定了它与激光功率和结构中微球数量之间的线性关系。依据这种线性关系推算了微球形成稳定链式结构所需的阈值功率,和实验中所观察的现象相符合。5.一维微球链整体动力学特性研究。比较了微球链和聚合物分子链的共同点和不同点,详细介绍了聚合物分子链基本的动力学模型:Rouse模型和Zimm模型。由于同时求解微球链中多个微球的运动方程存在很大的困难,因此在单个微球位置波动的基础上,采用彼此独立的模式将其组合以描述微球链的运动特性。建立了一般化的微球运动方程,介绍了描述微球间流体运动相互影响的张量。将迁移矩阵特征化得到微球链运动状态的本征模式,并通过已知Rouse模型和Zimm模型的仿真验证了其有效性。利用矩阵特征化方法求解了实际微球链的本征模式,并探索了本征模式自相关函数衰减时间的特性。6.二维结构中单体微球动力学特性的研究。在四光束倏逝波光阱中记录了微球在布朗运动作用下的位置波动,并验证了方形“晶格”结构。变换坐标系和去掉单元结构质心位置波动后,展示了微球相对位置波动的分布特性。根据其方差计算了各微球所处光阱的刚度,结果证实了微球单元结构中各微球受到相等的光力作用。
[Abstract]:The interaction of dispersed phase particles in the light and dispersion system contains the transfer of energy and momentum. The optical trap technique can restrict the characteristics of the motion of particles so that it is convenient for people to observe the dynamics of a single particle in the dispersion system, which is very useful for the study of the individual behavior of particles and the interaction between these particles. There are many microspheres in the optical trap, in which each microsphere is not only affected by the force from the background light field, but also influenced by the scattering light field and fluid motion from other microspheres. Under appropriate conditions, the multi microspheres can be gathered to form various structures, that is, the optical binding (Opitcal binding) phenomenon. Although the mechanical properties of the single particles in the optical trap are in spite of the mechanical properties of the optical trap It has been widely studied, but people tend to ignore the mechanical effects of the multi particle scattering light, so the quantitative study of the dynamics of multi microspheres appears relatively rough. At the same time, the evanescent wave optical trap provides a natural carrier for the optical binding phenomenon as a two-dimensional optical trap, and there is no quantitative study on the behavior of microspheres in tight structure. The observation and study of some phenomena can help people to understand the effect of light force and expand the new application. Based on these requirements, this paper observates the experimental phenomenon that the multi microspheres in the evanescent wave optical trap gather with the light force to form a small spaced one and two dimensional structures, and the quantitative analysis of the single microspheres by the position fluctuation of the microspheres is used. The main research work includes the following aspects: 1. Brown dynamics simulation of single microsphere. Compared with the usual calibration method of optical well stiffness, it is pointed out that both the azimuth shift method and the Boltzmann method do not require the viscosity information of the microsphere in the fluid. This property is helpful to the standard of the near plane evanescent wave optical well. By using the Monte Carlo method and the finite element method, the position and velocity iteration methods are used to simulate the position fluctuation of the single microspheres under the influence of limited Brown motion respectively, and their characteristics are compared. The concepts of the time of the velocity related memory and the related memory time of the position are introduced. Through the simulation results, the errors of the two are found. The calculation time of the position iterative method shortened the 3~4 magnitude significantly. In the simulation, it was found that when the stiffness difference between the two orthogonal directions in the optical trap was large, the selection of the two-dimensional coordinate system could have a significant influence on the correlation function of the microsphere position fluctuation. Finally, the microspheres were rotated under the external torque and influenced by the Brown motion. The characteristics of the position fluctuation of the microspheres are analyzed in three cases, that is, the main factors of the rotation displacement, the main factors of the Brown displacement and the situation between the two, and the analysis of the correlation function provides a method of measuring the transfer information of the microspheres.2. evanescent wave optical well system. A double beam evanescent wave optical trap system is used to observe the experimental phenomenon of one dimension chain structure of the microspheres with diameter 1umSiO2, and a four beam evanescent wave optical trap system is built. The experimental phenomenon of the formation of a two-dimensional structure of 1umSiO2 microspheres is observed..3. multi microsphere location detection algorithm is realized. The characteristics of the diffraction imaging of the microscope objective are described. The digital image of the point source in the image sensor under the set signal to noise ratio is simulated. The image analysis algorithm commonly used in the single microsphere location detection is compared. According to the motion characteristics of the observed microsphere chain, the existing extremum center method is improved. The detection time is shortened greatly on the premise of obtaining the same detection precision, and it is a multi microsatellite in the follow-up experiment. In the double beam evanescent wave optical trap, the SiO2 microspheres with diameter 1um form a compact one dimension microsphere chain under the action of light force in the double beam evanescent wave optical trap. The difference of the average interval between the microspheres under different conditions is analyzed and each microsphere is divided into each microsphere in the evanescent wave optical trap of a double beam. In the potential well, the stiffness of these potential wells can be obtained by the elastic coefficient of the spring between the microspheres in the ball spring model. The elastic coefficients of the spring are calculated in the chain structure under different conditions, and the quantity between the laser power and the number of the microspheres in the structure is determined for the first time in the experiment. Based on this linear relation, the threshold power required for the formation of a stable chain of microspheres is calculated. The whole dynamics characteristics of the.5. one-dimensional microsphere chain are studied in accordance with the observed phenomena in the experiment. The common points and different points of the microsphere chain and the polymer chain are compared, and the basic kinetics of the polymer molecular chain are detailed and detailed. Model: Rouse model and Zimm model. Because there is a great difficulty in solving the motion equations of microspheres in microspheres at the same time, on the basis of the fluctuation of the single microspheres, they are combined to describe the motion characteristics of the microspheres. A general microsphere motion equation is established, and the microsphere flow is described. The eigenmode of the motion state of the microsphere chain is obtained by characterizing the migration matrix, and the validity of the model is verified by the simulation of the known Rouse model and the Zimm model. The eigenmode of the actual microsphere chain is solved by the matrix characterization method, and the characteristic.6. of the eigenmode autocorrelation function is explored. The dynamic characteristics of a single microsphere in a two-dimensional structure are studied. In the four beam evanescent wave optical trap, the position fluctuation of the microspheres under the action of Brown is recorded and the square lattice structure is verified. The distribution characteristics of the position fluctuation of the microsphere phase are displayed after the change of the coordinate system and the position of the mass center of the removed unit. The stiffness of the optical trap at each microsphere is calculated. The results confirm that the microspheres in the microsphere structure are subjected to the same optical force.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O43

【相似文献】