CAREER: Unveiling the Stability, Rheology, and Topology of Active Fluids

该职业奖涉及新兴的活性流体领域，活性流体是一类由致密颗粒悬浮液组成的新型液体材料，可以通过将本地可用燃料的能量转化为运动来推动自己。活性流体在开发新材料和新产品方面具有巨大的潜力，但要实现这一潜力，就需要对这些流体所表现出的不寻常的材料特性和传输机制进行定量了解，这些特性和传输机制可能与惰性颗粒悬浮液的特性有很大不同。 本计画将联合收割机理论分析与数值模拟相结合，以建立一个完整的计算架构，用于复杂微流体环境中主动流体的建模、分析与控制。该项目将提供本科生和研究生培训，创造K-12外展机会，并支持虚拟现实包的开发，这将有助于解释研究成果和丰富课堂教学。虚拟现实软件包和演示将在网上向公众提供，沿着项目中开发的一些开放源码计算代码，这将使应用科学和工程领域的学生和研究人员受益。当悬浮在液体中时，运动的微粒对环境流施加应力，环境流作为耦合介质用于产生大规模的非稳定集体动力学。这些集中的系统往往表现出共同的特点，包括有序过渡，波动的密度，和力的产生。该项目的研究将采取下一步工程步骤，学习如何通过充分利用它们的集体行为来操纵活性流体。该项目包括四个研究方向：（1）开发一种混合算法，结合无穿透斯托克斯动力学粒子模拟和粗粒度有源液晶模型;（2）研究流体动力学不稳定性和相干流;（3）研究非平衡流变特性和拓扑结构;（4）设计用于新工程应用的有源液体超材料。混合算法将遵循自底向上的多尺度方法。微尺度离散粒子动力学将被用来建立连续动力学模型和新的极性液晶模型。计算框架将允许研究人员和从业人员通过在微观尺度上调整粒子活动和相互作用以及通过在宏观尺度上控制和引导受约束的相干流来控制活性流体。数值研究，连同支持实验验证，将导致跨尺度的动力学之间的联系的定量理解，并可能为输送流体和粒子的新的工程设备。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

This CAREER award involves emerging field of active fluids, which are a new class of liquid materials made up of densely packed suspensions of particles that can propel themselves by converting energy from locally available fuel into locomotion. Active fluids hold great potential for the development of new materials and products, but realizing this potential requires a quantitative understanding of the unusual material properties and transport mechanisms that these fluids exhibit, which can be much different than the properties of suspensions of inert particles. This project will combine theoretical analysis and numerical simulations to build a holistic computation framework for modeling, analysis, and control of active fluids in complex microfluidic environments. The project will provide undergraduate and graduate student training, create K-12 outreach opportunities, and support the development of a Virtual Reality package that will help interpret research results and enrich classroom teaching. The Virtual Reality package and demos will be available online to the general public, along with some of the open-source computation codes developed in the project, which will benefit both students and researchers in applied science and engineering.The physical properties of active fluids are fundamentally different from those of classical equilibrium systems. When suspended in a liquid, motile microparticles exert stresses on the ambient flows, which acts as a coupling medium for generating large-scale, unsteady collective dynamics. These concentrated systems often show common features, including ordering transition, fluctuating density, and force generation. The research in this project will take the next engineering step of learning how to manipulate active fluids by taking full advantage of their collective behaviors. The project consists of four research thrusts: (1) Develop a hybrid algorithm that combines penetration-free Stokesian dynamics particle simulations and coarse-grained active liquid crystal models; (2) Study the hydrodynamic instabilities and coherent flows; (3) Investigate non-equilibrium rheological properties and topological structures; and (4) Design active-liquid metamaterials for novel engineering applications. The hybrid algorithm will follow a bottom-up multiscale approach. The microscale discrete particle dynamics will be used to construct continuum kinetic models and new "polar" active liquid crystal models. The computational framework will permit researchers and practitioners to control active fluids by adjusting particle activity and interactions at the microscale, and by controlling and guiding constrained coherent flows at the macroscale. The numerical studies, together with supporting experimental verifications, will lead to quantitative understandings of the linkages between dynamics across scales, and possibly to new engineering devices for transporting fluids and particles.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.