Mixing, Migration, and Structure of Suspensions in Pressure-Driven Flows

中等颗粒体积分数的悬浮液在非线性剪切过程中易于分解。虽然这种效应已经在简单流动中进行了广泛的研究，以确定悬浮流变如何导致迁移，但很少有研究考虑在更复杂的流动中迁移是如何发生的。工业过程中的迁移长期以来一直是复杂的过程发展，随着研究人员努力处理和分析复杂生物机械流动中的血液和其他生物悬浮液，迁移变得越来越重要。本研究的目的是通过考虑流动中的基本对称性如何与底层悬浮结构相互作用来扩大我们对流动悬浮液的基本理解。在生物机械系统中常用的一维、二维和三维微通道流动中，将研究由多体流体动力相互作用引起的剪切迁移引起的悬浮液脱混与微通道内产生的混沌平流之间的竞争。直接测量流量和浓度分布将使用高速3D共聚焦激光扫描显微镜（CLSM）进行。该技术与停流扫描方案相结合，可以直接测量悬浮结构的各向异性，从而产生导致迁移的正应力。这些研究将扩展到技术相关流体的检查，包括多分散悬浮液、静电稳定悬浮液、粘弹性介质悬浮液和全血。由于流动、迁移和局部结构是直接使用CLSM确定的，因此可以检查添加单一大小悬浮液对细胞迁移和rouleau形成的影响。此外，连续介质模型将用于探索混沌流动中悬浮迁移与底层拓扑之间的耦合。本研究的智力优点和变革方面包括直接测量悬架结构的发展和展示流动悬架中混沌和分离之间的耦合。本研究的广泛影响包括使用混沌平流作为悬浮液自组织模板的新范式，可以彻底改变悬浮液处理从微观尺度到工业规模，全血分离和检测的潜在新平台，以及整合研究生，本科生，中学实践和基于网络的更广泛的粒子技术领域的学习。具体来说，将开发一个“本周图像”网站，向更广泛的社区展示这项研究和全校范围内的微尺度和纳米尺度研究的结果。同样，为了向早期科学家介绍更广泛的粒子技术主题，与当地一所中学合作开发一个探索颗粒介质的动手学习模块，将吸引来自社会经济地位较低的学生，以及工程和科学领域未被充分代表的少数群体。

Suspensions of a moderate particle volume fraction tend to demix in nonlinear shear. Although this effect has been studied extensively in simple flows to determine how suspension rheology results in migration, few studies have considered how migration occurs in more complicated flows. Migration in industrial processes has long complicated process development and has become increasingly important as researchers strive to process and analyze blood and other biological suspensions in complicated BioMEMS flows. The objectives of this research are to broaden our fundamental understanding of flowing suspensions by considering how the fundamental symmetries within flows interplay with the underlying suspension structure. In 1D, 2D and 3D microchannel flows commonly used in BioMEMS, the competition between suspension demixing via shear migration resulting from multibody hydrodynamic interactions and chaotic advection generated within microchannels designed to enhance mixing will be investigated. Direct measurement of flow and concentration profiles will be performed using high speed 3D confocal laser scanning microscopy (CLSM). This technique, coupled with a flow-stop-scan protocol, allows direct measurement of suspension structural anisotropy that generates the normal stresses that result in migration. These studies will be extended to examination of technologically relevant fluids, including polydisperse suspensions, electrostatic-stabilized suspensions, suspensions in viscoelastic media, and whole blood. Because flow, migration, and local structure is determined directly using CLSM, the effect of the addition of monosized suspension on cell migration and rouleau formation can be examined. In addition, continuum models will be used to explore the coupling between suspension migration and the underlying topology in chaotic flows. The intellectual merits and transformative aspects of this study include the development of directly measuring suspension structure and demonstrating the coupling between chaos and segregation in flowing suspensions. The broader impacts of this research include a new paradigm of using chaotic advection as a template for self-organization in suspensions that could revolutionize suspension processing from the microscale to industrial-scale, a potential new platform for whole blood fractionation and detection, and integration of graduate, undergraduate, middle school hands-on and web-based learning of the broader field of particle technology. Specifically, an Image of the Week website that presents the results of this research and university-wide microscale and nanoscale research to a broader community will be developed. Likewise, in order to introduce the broader subject of particle technology to early scientists, collaboration with a local middle school to develop a hands-on learning module for exploring granular media will engage students from low social economic status and otherwise underrepresented minority groups within engineering and the sciences.