Emergent Behaviors of Dense Active Suspensions Under Shear

非技术摘要溶液中由微小颗粒组成的致密悬浮液的流动对于从3D打印到半导体元件抛光的各种工业过程都是重要的。这个项目试图开发一种新的旋钮来操纵这种材料的流动。特别是，提出了粒子活性，即利用电场在单个粒子水平上以粒子旋转或其他运动的形式注入能量，可以发展成一种新型的旋钮来操纵流动悬浮液的性质。这项工作利用PI开发的一种新颖的组合实验、模拟和理论技术来绘制流动悬浮物中的活动可以诱导和确定推动这些流动变化的悬浮颗粒的潜在组织的行为范围。除了这些技术影响外，还建议开展一些教育和推广活动，包括科学交流讲习班、参加本科生暑期活动的研究经验，以及面向更广泛公众的各种推广活动。技术摘要活性物质已成为统计力学的一个主要分支，其中能量不是守恒的，而是在粒子水平上被注入系统。合成活性材料的巨大潜力之一是能够通过控制其组成的微观相互作用来调节其宏观块体性质。然而，到目前为止，大多数活性体系在制造可伸缩性方面都受到限制，这使得研究块体性质变得困难。该项目利用新的Quincke转子主动系统的开发，能够调查活动对悬浮液整体流变性的影响。拟议的工作重点放在密集3D区域中的活动的影响上，因为这是粒子相互之间以及与流动耦合最强的区域。特别是，它的目的是确定活性如何改变悬浮液的流变性，包括剪切增稠和堵塞转变。具体地说，建议使用实验、模拟和理论来确定：1)活性如何改变稠密悬浮体的剪切行为(例如增稠)；2)活性颗粒相互作用如何影响中尺度承载结构的形成；以及3)驱动这些行为的力网络是如何在空间上组织的。这些研究将提供一个新的旋钮，活性，用于调节悬浮液的流变行为，悬浮液是从3D打印到半导体工艺中抛光的重要材料系统。除了这些技术影响外，还建议开展一些教育和推广活动，包括科学交流研讨会、参与本科生活动的研究经验和各种推广活动。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical AbstractThe flow of dense suspensions comprised of microscopic particles in solution is important to a variety of industrial processes ranging from 3D printing to polishing of semiconductor components. This project seeks to develop a new knob for manipulating the flow of such materials. In particular, it is proposed that particle activity, i.e. using electric fields to inject energy in the form of particle rotations or other motions at the single particle level, can be developed into a novel knob for manipulating the properties of flowing suspensions. The work capitalizes on a novel combination experimental, simulation, and theory techniques developed by the PIs to map out the range of behaviors that activity in flowing suspensions can induce and determine the underlying organization of the suspended particles that drives these changes to the flow. In addition to these technological impacts, a number of education and outreach activities are proposed including science communication workshops, participation in research experience for undergraduate summer activities, and various outreach activities to the broader public.Technical AbstractActive matter has become a major branch of statistical mechanics where energy, rather than being conserved, is pumped into the system at the particle level. One of the great anticipated potentials of synthetic active materials is the ability to tune their macroscopic bulk properties through control of the microscopic interactions governing their constituents. To date, however, most active systems have been limited in their manufacturing scalability making it difficult to investigate bulk properties. This project capitalizes on the development of new Quincke rotor active systems that enable the investigation of the effect of activity on the bulk rheological properties of suspensions. The proposed work focuses on the effects of activity in the dense 3D regime since this is the regime where particles couple most strongly with one another and with the flow. In particular, it aims to determine how activity alters the rheological properties of suspensions including shear thickening and jamming transitions. Specifically, it is proposed to use experiments, simulations, and theory to determine: 1) how activity alters the shear behavior (e.g. thickening) of dense suspensions; 2) how the active particle interactions affect formation of mesoscale load bearing structures, and 3) how the force networks driving these behaviors are organized spatially. These investigations will provide a new knob, activity, for tuning the rheological behaviors of suspensions, an important material system for processes ranging from 3D printing, to polishing in semiconductor processes. In addition to these technological impacts, a number of education and outreach activities are proposed including science communication workshops, participation in research experience for undergraduate activities, and various outreach activities.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.