颗粒链孔迁移动力学特性的系统研究

It is ubiquitous that substances with a long-chain structure, such as granular chains or polymers, travel from one region to another region, only passing through the pore channel which connects both regions. The dynamic process is referred to as the pore translocation of long chains. Not only can the investigation on the pore translocation help to accelerate the progress of fast DNA sequencing, but to address some fundamental issues in the transport of complex fluid. In contrast with well-defined theoretical models and experiment measurements in polymer science, the studies for the pore translocation of granular chains are still absent. Consequently, it is very necessary to develop the research on the pore translocation of granular chains. In this proposal, we plan to establish experimental systems for the pore translocation in two-dimensions and three-dimensions. Then we measure the translocation time and record complete kinetic processes at the different conditions of external parameters. With using the simulation and classical ball-chain theory, we attempt to disclose the scaling relation between the translocation time or rate with the experimental parameters such as the chain length or external driving force. On the basis of experimental results and theoretical analyses, we further establish a universal model for the pore translocation of long chains by comparing and analogizing the concepts and the models in pore translocation of polymers. In conclusion, the studies on the pore translocation of granular chains can uncover the translocation mechanism, as well as potentially open a new avenue of research for polymer science.

长链材料（宏观颗粒链或者高分子链等）只能通过孔洞通道，从被该通道分离的区域A到达另一区域B的动力学过程被称为孔迁移。长链孔迁移研究不仅有助于解决如生物DNA快速测序等关键技术，而且也会帮助澄清复杂流体输运中的基础科学问题。相比已经开展了理论和实验研究的高分子链来说，现今宏观颗粒链孔迁移的模拟和测量工作依然缺乏。因此，非常有必要系统深入研究宏观链孔迁移。我们构建不同空间维度下的孔迁移实验体系，调控颗粒链自身物性和驱动外力等相关参数，通过测量记录迁移时间与迁移过程，结合理论分析与计算机模拟，揭示迁移时间、迁移率与材料参数之间的标度关系，建立普适长链孔迁移模型，类比分析高分子链孔迁移的结果，不仅可阐明宏观链迁移的物理机制，更可为高分子聚合物性质的研究提供新思路。

颗粒链孔迁移的研究不仅可进一步拓展与加深对颗粒物质的认识，有利于发展颗粒物理的基础理论；而且颗粒链在很多系统中已成为研究微观分子链的良好实验模型，对高分子理论起到积极的启发与验证作用，为高分子在孔迁移中的研究开辟新思路。本项目构建颗粒链二维孔迁移实验体系，调控颗粒链长、链的数量、链的自驱动性以及背景环境等实验参数，通过测量记录迁移时间与迁移过程，探究迁移时间、迁移率与材料参数之间的标度关系，与高分子链孔迁移的结果进行比较，建立相关模型合理解释实验结果。实验和理论结果表明，迁移时间随链长存在幂律关系，幂律指数随通道宽度增加而增加，且随通道宽度变大，其标度指数缓慢变小，符合标度律。幂律关系以及幂律指数随通道宽度的变化是由链水平动量的形式、迁移过程的摩擦效应以及进出口的熵力等共同作用所决定。将在颗粒热浴中的颗粒链与分子链在水溶液中的迁移行为进行比较，发现颗粒链系统与分子链系统在孔迁移时间与背景分子浓度上都具有转变特征，具有某种相似性。项目对自驱动颗粒链的单体、群体以及在复杂环境中的迁移动力学也进行了详细研究，单体迁移运动主要源自耗散对称性破缺，而群体迁移动力学受颗粒自驱动力强度、颗粒链数量、通道几何形状以及背景噪声决定，与布朗粒子浴相比，自驱动颗粒链在自驱动粒子中出现反常迁移，可能源于自驱动与颗粒链构型之间的耦合作用。