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下易于分层。 虽然这种影响已被广泛研究，在简单的流动，以确定如何悬浮液流变学迁移的结果，很少有研究考虑如何迁移发生在更复杂的流动。 工业过程中的迁移长期以来使过程开发变得复杂，并且随着研究人员努力在复杂的BioMEMS流中处理和分析血液和其他生物悬浮液而变得越来越重要。 这项研究的目的是扩大我们的基本理解流动悬浮液，考虑如何流动内的基本对称性与基本的悬浮结构相互作用。 在1D，2D和3D微通道流动中常用的BioMEMS，通过剪切迁移导致多体流体动力学相互作用和微通道内产生的混沌平流，以提高混合的悬浮液分层之间的竞争将被调查。 将使用高速3D共聚焦激光扫描显微镜（CLSM）直接测量流量和浓度分布。 这种技术，加上流动停止扫描协议，允许直接测量悬浮液结构各向异性，产生的正常应力，导致迁移。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，粘弹性介质中的悬浮液和全血。 由于流动，迁移和局部结构直接使用CLSM确定，因此可以检查添加单一尺寸的悬浮液对细胞迁移和rouleau形成的影响。 此外，连续介质模型将被用来探索悬浮迁移和混沌流的底层拓扑结构之间的耦合。 这项研究的智力价值和变革方面包括直接测量悬浮结构的发展，并展示了流动悬浮液中的混沌和分离之间的耦合。 这项研究的更广泛的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尺度到工业规模，全血分离和检测的潜在新平台，以及研究生，本科生，中学实践和基于网络的学习粒子技术的更广泛领域的整合。 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大学范围内的微米级和纳米级研究的结果。 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媒体的实践学习模块，将吸引社会经济地位较低的学生和工程和科学领域代表性不足的少数群体。

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.