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Colloidal Mikado: Self-motion of a stiff slender rod in a maze of linelike obstacles

胶体天皇：一根坚硬细长的杆在线状障碍物迷宫中的自我运动

基本信息

批准号：
218924699
负责人：
Professor Dr. Thomas Franosch
金额：
--
依托单位：
Institut für Theoretische Physik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/218924699?language=en
关键词：
Colloidal Mikado Self motion stiff

项目摘要

Strongly hindered transport of highly elongated micron- and submicron-sized objects is of fundamental interest both from a purely theoretical point of view as well for various applications ranging from emulsions in the food industry, dense solutions of viruses to the complex viscoelastic response of biological networks. Already the free motion of needle-like objects such as fibers, biofilaments, or nanotubes in solution is anisotropic due to hydrodynamic coupling to the solvent, however the ratio of the diffusion along and perpendicular to the axis can never exceed the value of 2. In contrast in dense needle liquids, the motion of a single rodlike objects is almost entirely along its axis implying that anisotropies can become arbitrarily large. The strong mutual interactions of the rods give rise to peculiar complex dynamics of the solution characterized by a pronounced rotation-translation coupling. The goal of the project is to delevelop a complete theoretical characterization of the selfdynamics of slender rod of high aspect ratio in a semidilute suspension of rods. The statistical properties of transport will be characterized in terms of a generalized van Hove correlation function, i.e. the probability distribution that the rod has travelled a certain distance while reorienting to a new direction in a prescribed lagtime, provided its initial position and orientation was known. From this conditional probability all two-time correlation functions such as the mean-square displacements, mean-quartic displacements, the orientational correlation function, or the intermediate scattering functions can calculated. The theory will be based on an effective medium approach, where the needle moves in a homogeneous medium, yet the presence of the surrounding needles gives rise to peculiar material properties of this medium. The theoretical predictions will be validated by extensive computer simulations both for a simplified model, where only the tracer is allowed to move, as well as for a liquid of needles, where all particles are treated on equal footing. We believe that such a combined approach of theoretical advancement and computer simulation study will be useful to understand even more complex transport phenomena occuring in suspension of filaments or networks.

无论是从纯理论的角度，还是从食品工业中的乳剂、病毒的密集溶液到生物网络的复杂粘弹性响应等各种应用的角度来看，高度细长的微米和亚微米大小物体的强阻碍运输都具有根本的意义。针状物体（如纤维、生物丝或纳米管）在溶液中的自由运动由于与溶剂的流体动力耦合而具有各向异性，但是沿轴和垂直轴的扩散比永远不会超过2。相反，在密集的针状液体中，单个棒状物体的运动几乎完全沿着其轴线，这意味着各向异性可以变得任意大。棒的强相互作用产生了以明显的旋转-平移耦合为特征的特殊复杂动力学。该项目的目标是开发一个完整的理论表征的自动力学的细长杆高长径比在半稀悬架杆。传输的统计特性将用一个广义的van Hove相关函数来表征，即在已知其初始位置和方向的情况下，棒子在规定的滞后时间内移动了一定距离并重新定向到新方向的概率分布。从这个条件概率可以计算出所有的两次相关函数，如均方位移、均四次位移、方向相关函数或中间散射函数。该理论将基于有效介质方法，其中针在均匀介质中运动，但周围针的存在会产生该介质的特殊材料特性。这些理论预测将通过广泛的计算机模拟得到验证，模拟对象包括简化模型（只允许示踪剂移动）和针状液体（所有粒子都被平等对待）。我们相信，这种理论进步和计算机模拟研究相结合的方法将有助于理解在细丝或网络悬浮物中发生的更复杂的输运现象。