Active Fluids in Externally Driven Flows

这项研究将为主动流体的设计和控制提供理论框架。活性流体由能量驱动，该能量以构成流体的颗粒的小尺度添加。例如，我们细胞中的胞质溶胶流动是因为分子马达消耗储存能量的ATP分子，并利用这种能量使刚性生物聚合物相互滑动。这种滑动运动诱导可用于细胞爬行或细胞内生物材料运输的流动。目前，人们对开发人工活性物质系统，例如泵送自身的微流体装置有很大的兴趣。了解流体的流体动力学性质是必不可少的，如果他们曾经是在医学或工业中的实际用途。本研究的重点是数学模型的主动流体的流动时，它受到外部驱动的流动，如由泵驱动的流动。理论计算的结果将与实验进行比较，以确定控制主动流性质的参数。这项研究将支持本科生和研究生的科学培训。PI将通过领导联盟夏季研究早期识别计划，指导来自工程和物理科学历史上代表性不足的群体的本科生。与这项工作有关的主题将被纳入工程和物理学的本科和研究生课程。很少有研究活动的物质受到外部流动。本研究的目的是研究活性凝胶的流体动力学，即活性非极性细丝，其被充分稀释，它们往往不会自发地排列并形成液晶相。线性稳定性分析和数值计算将被用来研究的活性驱动的流动转换在两个维度的活性凝胶受到外部流的Couette，Poiffille，和泰勒-Couette类型。模拟将被用来探讨在盖子驱动的空腔流的活性凝胶的约束的效果。最后，将研究活性凝胶的三维通道流动，以及阻力和扭矩以及活性凝胶中物体的自发运动。该奖项反映了NSF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.