IMECH-IR  > 国家微重力实验室
Alternative TitleDiffusion behavior of non-spherical colloidal particles in confined space
Thesis Advisor王育人 ; 郑中玉
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline一般力学与力学基础
Keyword胶体粒子 受限空间 非球形 扩散行为 流体动力学相互作用












Other Abstract

Colloids is an important research area of soft matter. Recent years, more and more attention has been paid to the study of colloidal systems, due to their unique physical, mechanical, chemical and biological characteristics.

The diffusion behaviors of non-spherical colloidal particles in confined space are widely encountered in nature, industrial production and basic scientific research. Different from the simple Brownian diffusion of isotropic particles in unconstrained space, the shape of non-spherical colloidal particles will lead to the anisotropy of the diffusion behavior, and the diffusion behaviors are also affected by the spatial constraint and the interactions between colloidal particles, thus increasing the difficulty of this research. Over the past decades, researchers have conducted extensive research on how these three factors affect the diffusion behavior of colloidal particles. However, the theoretical research on the diffusion behavior of non-spherical colloidal particles in quasi-one-dimensional confinement is insufficient, and there is no relevant experimental research. This research plays an important role in guiding the practical problems, such as blood vessel flow, microchannel chip design, and drug delivery and so on. It also plays an important role in expanding and improving the research field of the diffusion behavior of anisotropic colloidal particles in confined space.

In this paper, experimental observation, theoretical analysis and computer numerical simulation are considered to study these problems systematically.

Polystyrene (PS) ellipsoidal particles with controllable aspect ratios are fabricated by controlled deformation method. Silicon wafer substrates are fabricated by photolithographic mask method and polydimethylsiloxane (PDMS) channel models are obtained by molding method. Using fluorescence microscopy, we observed and recorded the Brownian motion of ellipsoidal particles in various experimental systems. The trajectory data of ellipsoidal colloidal particles are obtained by image particle tracking technique, and characteristic parameters such as diffusion coefficients, mean squared displacement (MSD) and radial distribution function of ellipsoidal particles are calculated by MATLAB.

In the experimental observation, we obtained some novel experimental observations:

(1) The isolated ellipsoid particles Brownian diffusing in a quasi-one-dimensional (q1D) channel shows stable stratification, and its long axis nearly parallel to the direction of channel.

(2) Two adjacent Brownian ellipsoidal particles in a q1D channel are located symmetrically in the centre of the channel. Their short-term self-diffusion coefficients change obviously with the change of their separation distance, and the self-diffusion appears a crossover region, in which the diffusion coefficient increase with the increasing time, in the intermediate time regime.

(3) The translation-translation coupling diffusion of two adjacent ellipsoidal particles diffusing in a q1D channel changes from positive to anomalous negative correlation with the increase of their transverse separation.

These novel experimental phenomena have rarely been reported in previous studies. With reasonable assumptions, we proposed the corresponding rectangular channel model and cylinder-dumbbell point force model to different experimental systems. Thus the theoretical solutions of characteristic parameters which correspond to experimental data in various experimental systems are obtained through theoretical derivation. By using finite element analysis software, the finite element numerical simulations of the relevant problems are carried out, and the flow field and numerical simulation results of characteristic parameters are obtained.

The rationality of the theoretical model is verified by comparing various characteristic parameters obtained by experimental observation, theoretical derivation and finite element numerical simulation. We can explain how particle shapes, spatial constraints, and hydrodynamic interaction affect particles self-diffusion behaviors. As a result, the physical nature of these novel experimental phenomena is revealed.

These studies will deepen and expand our understanding on how colloidal particle shapes, spatial constraints affect their self-diffusion, the hydrodynamic interaction between them and other issues. It also provides theoretical guidance for drug delivery, microfluidic chip design and other practical applications.

Document Type学位论文
Recommended Citation
GB/T 7714
李瀚海. 受限空间中非球形胶体的粒子扩散行为研究[D]. 北京. 中国科学院大学,2019.
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