Cooperative Motion of Microswimmers: The Influence of Ionic and Reactive Screening on Hydrodynamic Interactions in Complex Fluids

微型游泳者的协作运动：离子和反应筛选对复杂流体中水动力相互作用的影响

• 批准号: 254456455
• 负责人: Professor Dr. Christian Holm
• 金额: --
• 依托单位: Institut für Computerphysik (ICP)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/254456455?language=en
• 关键词: Cooperative; Motion; Microswimmers; Influence; Ionic

In this project, we will study the effect of electrostatic and reactive screening on the collective dynamics of chemically driven microswimmers in complex media -- specifically, fluids with viscoelastic response -- using computational methods. The ultimate goal is to achieve a better understanding of the interplay of swimmers' contact, (elasto)hydrodynamic, and phoretic (chemical) interactions that underlie the cooperative behavior observed in a large variety of real-world systems. For example, for chemical model systems, which have recently gained experimental attention within the active matter community, an improved understanding of the propulsion mechanisms may give insights into the way bacteria invade the protective viscoelastic mucus lining our vital organs. Our project aims to contribute to this effort by studying currently available model systems from a more fundamental perspective.We have recently considered a variety of self-electrophoretic systems, e.g., Janus colloids in a hydrogen peroxide solution, where we have theoretically demonstrated that their self-propulsion can be strongly modulated by bulk ionic reactions that induce reactive screening. We will extend these single particle results in this SPP funding period to encompass the collective dynamics of these systems. To this end, we will model the active particles using our lattice-electrokinetics (lattice-EK) algorithm, developed during the previous SPP funding period. Lattice-EK exploits the computational efficiency of the lattice-Boltzman (LB) algorithm for hydrodynamics and combines this with powerful numerical solvers for solute concentration and electrostatic fields. This efficiency enables us to simulate the interaction between many chemical swimmers and explore the way collective motion comes about, while giving us full control over all elements included in the modelling. Our lattice-EK is state of the art, as it is capable of simulating moving boundary conditions for charged systems, a first of its kind for this type of algorithm.Our strategy for this SPP funding period is to make further algorithmic improvements to the lattice-EK in order to facilitate the study of collective motion and to better recover the relevant physics. These modifications include adaptive grid refinement and lubrication corrections, as well as bringing together lattice-EK and viscoelastic LB methods. Simultaneously, we will use our software to investigate a number of swimmer systems that are experimentally realized by our SPP collaborators, and systematically characterize the collectivity therein. By following this approach, our project will lead to an improved understanding of the key parameters that bring about the complex out-of-equilibrium behavior of actively driven particles.

在这个项目中，我们将研究静电和反应屏蔽对化学驱动的微泳者在复杂介质中的集体动力学的影响-特别是粘弹性响应的流体-使用计算方法。最终的目标是实现更好地理解游泳者的接触，（弹性）流体动力学和泳（化学）相互作用的相互作用，在大量的各种现实世界的系统中观察到的合作行为的基础。例如，对于化学模型系统，最近在活性物质社区中获得了实验关注，对推进机制的更好理解可能会让我们深入了解细菌入侵我们重要器官的保护性粘弹性粘液的方式。我们的项目旨在通过从更基本的角度研究当前可用的模型系统来为这一努力做出贡献。我们最近考虑了各种自电泳系统，例如，Janus胶体在过氧化氢溶液中，在那里我们已经从理论上证明了它们的自推进可以强烈调制的散装离子反应，诱导活性筛选。我们将在SPP资助期间扩展这些单粒子结果，以涵盖这些系统的集体动力学。为此，我们将使用我们的晶格电动力学（lattice-EK）算法对活性粒子进行建模，该算法是在上一个SPP资助期间开发的。Lattice-EK利用格子玻尔兹曼（LB）算法的计算效率进行流体力学，并将其与溶质浓度和静电场的强大数值求解器相结合。这种效率使我们能够模拟许多化学游泳者之间的相互作用，并探索集体运动的方式，同时让我们完全控制建模中包含的所有元素。我们的lattice-EK是最先进的，因为它能够模拟带电系统的移动边界条件，这是此类算法的第一种。我们在SPP资助期间的策略是对lattice-EK进行进一步的算法改进，以促进集体运动的研究，并更好地恢复相关的物理。这些修改包括自适应网格细化和润滑校正，以及汇集格EK和粘弹性LB方法。同时，我们将使用我们的软件来研究一些由我们的SPP合作者实验实现的游泳者系统，并系统地描述其中的集体性。通过遵循这种方法，我们的项目将导致对导致主动驱动粒子的复杂失衡行为的关键参数的更好理解。