CAREER: Mixing and Vorticity Dynamics in Active Fluid Systems

这个CAREER项目将探索主动流体系统的混合动力学和运动学。研究人员和工业从业者经常使用微流控技术来处理微量流体，从而最大限度地减少浪费，提高灵活性和效率。微流体系统控制流体的尺度非常小，通常小于一毫米。微流控技术的进步受到了小尺度混合的挑战，因为在非常小的通道中很难产生湍流。主动流体是含有离散实体的流体，它们在自身的动力下运动，可能会促进局部混合。即使在很小的空间里，活跃的流体也会产生湍流，促进微混合。本研究将探索活动流体的混合过程和涡旋动力学，包括描述该过程的方程，不同流体活动和边界条件的影响，以及活动流体与非活动流体结合的影响。由此产生的知识将刺激新的微混合技术的发展，这将提高化学工程和制药工业的生产效率，使产品能够按需合成，并减少储存和运输危险或反应性化学品的需要。该项目还将通过混合两种不同颜色的面团的比赛和在线活性物质模拟程序，为K-12学生提供混合动力学的实践经验。该项目还将包括一个在线教师培训模块，以帮助将活跃物质概念引入美国课堂。活跃湍流已经被描述和模拟，但是对于活跃湍流如何促进混合知之甚少。一些基本问题仍未得到解答，如“活性流体系统的混合效率是多少？”以及“哪些参数控制活性流体的混合效率？”为了解决这些问题并扩展有关主动湍流诱导混合的知识，将通过修改已建立的用于表征主动湍流的主动线虫流体动力学方程来模拟微管-动力蛋白主动流体的混合过程。该项目将扩展现有的活动线虫流体动力学模型，以描述具有非均匀活动、移动边界和多种流体的活动流体系统。该扩展模型将通过相关实验进行验证，将指导主动流体在科学和工业中的应用，并允许工程师有效地探索参数空间，以优化新型自混合系统，特别是在微米尺度上。该项目将连接两个已建立的领域——混合和主动流体建模——从而将已建立的混合理论扩展到包括主动流体，并阐明主动流体和被动流体混合之间的差异。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 CAREER project will explore the mixing dynamics and kinematics of active fluid systems. Researchers and industrial practitioners often use microfluidic technology to process tiny quantities of fluids, which minimizes waster and enhances flexibility and efficiency. Microfluidic systems manipulate fluids at a very small scale, typically smaller than one millimeter. Progress in microfluidic technology is limited by the challenge of mixing at a small scale, because it is difficult to generate turbulence at in very small channels. Active fluids are fluids containing discrete entities that move under their own power and may be able to promote local mixing. Even in tiny spaces, active fluids can generates turbulence and promote micromixing. This research will explore the mixing process and vortex dynamics of active fluids, including the equations that describe the process, the effects of varying fluid activity and boundary conditions, and the effects of combining an active fluid with an inactive fluid. The resulting knowledge will stimulate development of new micromixing technologies that will increase production efficiency in the chemical engineering and pharmaceutical industries, enable products to be synthesized on demand, and reduce the need to store and transport hazardous or reactive chemicals. This project will also provide K-12 students with hands-on experiences in mixing dynamics through a contest mixing two different colors of dough and an online active matter simulation program. This project will also include an online teacher training module to help bring active matter concepts to US classrooms.Active turbulence has been characterized and modeled, but little is known about how active turbulence facilitates mixing. Several fundamental questions remain unanswered, such as, “What is the mixing efficiency of an active fluid system?” and “What parameters control the mixing efficiency of active fluid?” To address these questions and expand knowledge about active turbulence-induced mixing, the mixing process of microtubule-kinesin active fluid will be modeled by modifying established active nematohydrodynamic equations developed to characterize active turbulence. This project will extend the existing active nematohydrodynamic model to describe active fluid systems with inhomogeneous activity, a moving boundary, and multiple fluids. The expanded model, which will be validated with accompanying experiments, will guide the application of active fluid in science and industry and allow engineers to efficiently explore parameter space to optimize novel self- mixing systems, particularly at the micron scale. This project will connect two well-established fields— mixing and active fluid modelling —and thus extend established mixing theory to include active fluids and elucidate differences between how active and passive fluids mix.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.