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，我们将使用计算方法研究静电和反应屏蔽对复杂介质（特别是具有粘弹性响应的流体）中化学驱动微型游泳器的集体动力学的影响。最终目标是更好地理解游泳者接触、（弹力）流体动力学和泳动（化学）相互作用的相互作用，这些相互作用是在各种现实世界系统中观察到的合作行为的基础。例如，对于最近在活性物质界引起实验关注的化学模型系统，对推进机制的更好理解可能有助于了解细菌侵入我们重要器官内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项工作做出贡献。我们最近考虑了各种自电泳系统，例如过氧化氢溶液中的 Janus 胶体，我们从理论上证明了它们的自电泳系统-推进可以通过引发反应筛选的大量离子反应来强烈调节。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，我们将使用在上一个 SPP 资助期间开发的晶格电动 (lattice-EK) 算法对活性粒子进行建模。 Lattice-EK 利用了流体动力学的格子玻尔兹曼 (LB) 算法的计算效率，并将其与强大的溶质浓度和静电场数值求解器相结合。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，并探索集体运动的发生方式，同时使我们能够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，这是此类算法中的第一个。我们在本次SPP资助期间的策略是对点阵进行进一步的算法改进-EK为了促进集体运动的研究并更好地恢复相关物理。这些修改包括自适应网格细化和润滑校正，以及将晶格 EK 和粘弹性 LB 方法结合在一起。同时，我们将使用我们的软件来研究由我们的 SPP 合作者通过实验实现的许多游泳者系统，并系统地表征其中的集合。通过采用这种方法，我们的项目将更好地理解导致主动驱动粒子的复杂非平衡行为的关键参数。