Active Fluids in Externally Driven Flows

本研究将为主动流体的设计和控制提供理论框架。主动流体是由组成流体的小颗粒所增加的能量驱动的。例如，细胞内的细胞质流动是因为分子马达消耗了储存能量的ATP分子，并利用这种能量使刚性生物聚合物相互滑动。这种滑动运动产生的流动可用于细胞爬行或细胞内生物材料的运输。目前，人们对开发人工活性物质系统非常感兴趣，例如一种可以自我泵送的微流体装置。了解活性流体的流体动力学性质是必要的，如果他们曾经是在医药或工业上的实际应用。本研究的重点是在受到外部驱动流（如泵驱动流）的情况下，对活动流体的流动进行数学建模。理论计算结果将与实验结果进行比较，以确定控制主动流性质的参数。本研究将为本科生和研究生的科学培养提供支持。这些pi将通过领导力联盟夏季研究早期识别项目，指导工程和物理科学领域历史上代表性不足的群体的本科生。与这项工作相关的主题将被整合到工程和物理的本科和研究生课程中。对受外部流动影响的活性物质的研究很少。本研究的目的是研究活性凝胶的流体动力学，即活性极性细丝被充分稀释，它们往往不会自发排列并形成液晶相。采用线性稳定性分析和数值计算的方法，研究活性凝胶在库埃特、泊泽维尔和泰勒-库埃特三种外源流作用下活性驱动的二维流动转变。模拟将用于探索限制对活性凝胶在盖子驱动的空腔流动的影响。最后，将研究活性凝胶的三维通道流动，以及活性凝胶中物体的阻力和扭矩以及自发运动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research will develop the theoretical framework for the design and control of active fluids. Active fluids are driven by energy which is added at the small scale of the particles that make up the fluid. For example, the cytosol in our cells flows because molecular motors consume energy-storing ATP molecules and use this energy to slide rigid biopolymers past each other. This sliding motion induces flows that can be used for cell crawling or the transport of biological materials within the cell. There is currently great interest in developing artificial active matter systems, such as a microfluidic device which pumps itself. Understanding the hydrodynamic properties of active fluids is essential if they are ever to be of practical use in medicine or industry. The focus of this research is to mathematically model the flow of an active fluid when it is subject to an externally driven flow, such as the flow driven by a pump. The results of theoretical calculations will be compared with experiments to determine the parameters that control the nature of active flow. This research will support the scientific training of undergraduate and graduate students. The PIs will mentor undergraduates from historically underrepresented groups in engineering and physical science through the Leadership Alliance Summer Research Early Identification Program. Topics related to this work will be integrated into undergraduate and graduate courses in engineering and physics. There are very few studies of active matter subject to external flows. The goal of this research is to study the fluid dynamics of active gels, i.e. active apolar filaments that are sufficiently dilute that they tend not to spontaneously align and form a liquid crystalline phase. Linear stability analysis and numerical computation will be used to study the activity-driven flow transitions in active gels in two dimensions subject to external flows of Couette, Poiseuille, and Taylor-Couette types. Simulations will be used to explore the effect of confinement on active gels in lid-driven cavity flow. Finally, three-dimensional channel flows of active gels will be studied, as well as the drag forces and torques and spontaneous motion of objects in an active gel.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.