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Motile colloids with tunable random walk: individual dynamics and collective behavior

具有可调随机游走的运动胶体：个体动力学和集体行为

基本信息

批准号：
2004926
负责人：
Petia Vlahovska
金额：
$ 56.11万
依托单位：
Northwestern University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-15 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2004926&HistoricalAwards=false
关键词：
Motile colloids tunable random walk

项目摘要

Non-technical Abstract:Flocks of birds and schools of fish are familiar examples of emergent collective behavior, where interactions between self-propelled (active) individuals lead to coherent motion on a scale much larger than the isolated unit. Similar phenomena have been observed with active micro-particles such as bacteria and motile colloids. Recently, the Quincke instability (spontaneous spinning of a dielectric particle in an applied uniform DC field) has attracted great interest as a means of propelling colloids, by simply letting the particles roll on a surface. The research team lead by Petia Vlahovska has found that Quincke rollers can be designed to perform Run-and-Tumble-like locomotion mimicking bacteria such as E. coli. Populations of the Quincke random walkers self-organize and exhibit behaviors reminiscent of bacterial suspensions such as dynamic clusters and mesoscale turbulent-like flows. However, the physical mechanisms underlying the self-organization are unknown. To fill this void, the research team will carry out a combined experimental and theoretical study that systematically explores the parameter space of particle density, activity, shape and motility pattern of the individual colloid. In addition to advancing basic knowledge, the research outcomes may lead to the design of novel active materials (e.g., suspensions with microstructure and effective viscosity tunable by electric field). The visually appealing nature of the experiments will excite students and the general public about active matter and electrohydrodynamics. The principal investigator will be involved in the successful outreach programs at Northwestern University to translate the relevance and significance of this work to attract students from underrepresented groups in science and engineering.Technical Abstract:Active particles such as swimming bacteria or self-propelled colloids spontaneously assemble into large-scale dynamic structures. The emergence of the collective states from the motility pattern of the individual particles, typically a random walk, is yet to be probed in a well-defined synthetic system. The Quincke random walker is a promising new experimental platform to explore active locomotion at the microscale and a testbed for the abundant theoretical models of the collective dynamics of active matter. For the first time, the collective dynamics of run-and-tumble microswimmers will be experimentally studied under well defined and controllable conditions e.g., particle density, speed (i.e., activity) and locomotion type (e.g., run-and-tumble and Levy walks), which can yield potentially transformative knowledge about the relation between the macroscale dynamics and the microswimmers motion and interactions. The experimental research will be complemented by theoretical modeling of the Quincke-walker dynamics, using microhydrodynamics approaches, to elucidate the physical mechanisms of the observed phenomena. The project integrates knowledge across the fields of fluid mechanics and soft matter, and thus the principal investigator anticipates both a much deeper understanding of the underlying physics as well as the discovery of new dynamical regimes and engineering opportunities. The research is interdisciplinary which will be very beneficial for the education and development of the students associated with the project.This Division of Materials Research (DMR) grant supports research to develop a novel experimental platform and the planned experiments and simulations for understanding the emergence of self-organization with funding from the Condensed Matter Physics (CMP) Program in DMR of the Mathematical and Physical Sciences Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要：鸟群和鱼群是新兴集体行为的常见例子，其中自我推进（主动）个体之间的相互作用导致比孤立单位大得多的规模的连贯运动。在细菌和运动胶体等活性微粒中也观察到了类似的现象。最近，昆克不稳定性（介电粒子在施加的均匀直流场中自发旋转）作为一种推动胶体的手段（通过简单地让粒子在表面上滚动）引起了人们的极大兴趣。 Petia Vlahovska 领导的研究小组发现，Quincke 滚轮可以设计成模仿大肠杆菌等细菌进行类似奔跑和翻滚的运动。昆克随机游走者群体会自组织并表现出类似细菌悬浮液的行为，例如动态簇和中尺度湍流。然而，自组织背后的物理机制尚不清楚。为了填补这一空白，研究小组将进行实验和理论相结合的研究，系统地探索单个胶体的颗粒密度、活性、形状和运动模式的参数空间。除了推进基础知识之外，研究成果还可能导致新型活性材料的设计（例如，具有微结构和可通过电场调节有效粘度的悬浮液）。实验的视觉吸引力将使学生和公众对活性物质和电流体动力学感到兴奋。首席研究员将参与西北大学成功的外展项目，以转化这项工作的相关性和意义，以吸引来自科学和工程领域代表性不足群体的学生。技术摘要：活性粒子，如游动细菌或自驱动胶体，自发地组装成大规模动态结构。从单个粒子的运动模式（通常是随机游走）中出现的集体状态尚未在明确定义的合成系统中进行探讨。 Quincke 随机行走器是一个有前途的新实验平台，用于探索微观尺度的主动运动，也是活跃物质集体动力学丰富理论模型的测试平台。首次，将在明确和可控的条件下对奔跑和翻滚微型游泳者的集体动力学进行实验研究，例如粒子密度、速度（即活动）和运动类型（例如奔跑和翻滚和利维行走），这可以产生有关宏观动力学与微型游泳者运动和相互作用之间关系的潜在变革性知识。实验研究将通过使用微流体动力学方法的昆克-沃克动力学理论建模来补充，以阐明所观察到的现象的物理机制。该项目整合了流体力学和软物质领域的知识，因此首席研究员预计对基础物理学有更深入的了解，并发现新的动力学机制和工程机会。该研究是跨学科的，这对于与该项目相关的学生的教育和发展非常有益。该材料研究部 (DMR) 拨款支持研究开发新颖的实验平台以及计划的实验和模拟，以了解自组织的出现，资金来自数学和物理科学理事会 DMR 凝聚态物理 (CMP) 项目。该奖项反映了 NSF 的法定使命，并具有通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。