Hydrodynamic Crystals: Structural Evolution in Confined Suspension Flows

从细菌菌落动力学到微流体动力学，了解微受限悬浮流动中的集体流体动力学现象在各个研究领域都至关重要。然而，这些现象还远未被理解。为了阐明颗粒系统的集体流体动力学，我们建议研究平行壁面通道中强约束有序悬浮液的演化。我们将研究两种系统：仅通过水动力相互作用的粒子阵列，以及流动驱动的胶体晶体，其中粒子有序源于势和水动力。我们对流动驱动有序粒子阵列的初步研究表明，这些系统表现出波动传播、粒子晶格的突然重排、有序无序转变和指指不稳定性。使用数值，实验和理论方法，我们将研究产生这种丰富的动力行为的水动力机制。我们的研究见解将为颗粒流动的基本问题提供新的思路，将适用于其他有序耗散系统，并将为实际应用提供新的策略（例如，多滴微流体装置和颗粒涂层流动）。所提出的数值模拟将使用我们新颖的精确和高效的Stokesian动力学算法进行。实验部分将包括使用全息光学镊子组装规则的二维粒子阵列，并使用共聚焦显微镜观察悬浮结构的变化。我们的理论研究将涉及规则粒子阵列中位移波的傅立叶分析和描述阵列演化和不稳定性的有效介质方法。智力价值：我们提出的研究的智力价值既基本又实用。我们将研究蠕变颗粒流中一类全新的水动力现象。我们的研究结果将与非线性物理相关（包括复杂流体动力学、尘埃等离子体中的结构演化和超导体中通量漩涡的集体运动）。我们的研究结果也将对工程应用产生重大影响，特别是在微流体领域。新兴的多滴微流控应用包括可调谐光学器件、高通量芯片上实验室分析和制造微结构材料。了解在强约束条件下控制悬架结构的水动力机制是此类应用的关键，我们提出的研究将揭示这些机制。更广泛的影响：该项目将为研究生、本科生和高中生提供教育和研究机会。研究生和本科生将在新英格兰复杂流体研讨会和国家科学会议上展示他们的工作。来自代表性不足群体的学生将通过耶鲁大学的STARS（科学、技术和研究学者）项目被招募。这些pi将通过担任纽黑文科学博览会的评委来支持大纽黑文的K-12教育。我们项目的跨学科意义在于获得的结果将用于图案形成的物理，物理化学和微流体技术。我们研究的见解也将适用于涉及集体流体动力学效应的生物科学研究，例如细菌运动的研究。粒子跟踪软件和一些斯托克动力学代码将通过免费网站传播。这项研究还涉及国际合作。

0931504BlawzdziewiczUnderstanding of collective hydrodynamic phenomena in microconfined suspension flows is crucial in diverse research fields that range from dynamics of bacterial colonies to microfluidics. Such phenomena, however, are far from being understood. To elucidate collective hydrodynamics of particulate systems we propose to investigate the evolution of strongly confined ordered suspensions in parallel wall channels. We will study two kinds of systems: particle arrays interacting only via hydrodynamic forces, and flow driven colloidal crystals where particle ordering stems from potential and hydrodynamic forces. Our preliminary studies of flow driven ordered particle arrays reveal that these systems show wave propagation, sudden rearrangements of particle lattice, order disorder transitions, and fingering instabilities. Using numerical, experimental and theoretical methods, we will investigate hydrodynamic mechanisms that produce this rich dynamical behavior. Insights from our studies will shed new light on basic questions of particulate flows, will be applicable to other ordered dissipative systems, and will also suggest new strategies for practical applications (e.g., multidrop microfluidic devices and particulate coating flows). The proposed numerical simulations will be performed using our novel Stokesian dynamics algorithm that is accurate and highly efficient. The experimental part will consist in assembling regular 2D particle arrays using holographic optical tweezers, and observing changes in suspension microstructure using confocal microscopy. Our theoretical investigations will involve Fourier analysis of displacement waves in regular particle arrays and an effective medium approach to describe the evolution and instabilities of the arrays.Intellectual Merit: The intellectual value of our proposed research is both fundamental and practical. We will study an entirely new class of hydrodynamic phenomena in creeping particulate flows. Our results will be relevant to nonlinear physics (including dynamics of complex fluids, structural evolution in dusty plasma, and collective motion of flux vortices in superconductors). Our results will also have significant impact on engineering applications, especially in microfluidics. Emerging multidrop microfluidic applications include tunable optical devices, high throughput lab-on-chip assays, and manufacturing microstructured materials. Understanding hydrodynamic mechanisms governing suspension structure under strong confinement conditions is key in such applications, and our proposed research will uncover such mechanisms.Broader Impact: This project will provide educational and research opportunities for graduate, undergraduate and high school students. Graduate and undergraduate students will present their work at New England Complex Fluids Workshops and at national scientific meetings. Students from under represented groups will be recruited through the STARS (Science, Technology and Research Scholars) program at Yale. The PIs will support K-12 education in Greater New Haven by serving as judges in New Haven science fairs. Interdisciplinary significance of our project consists in obtaining results that will be used in physics of pattern formation, physical chemistry, and microfluidic technology. Insights from our research will also be applicable to biological sciences in investigations involving collective hydrodynamic effects, e.g., in studies of bacterial motion. Software for particle tracking and some of the Stokesian dynamics codes will be disseminated through free websites. This research also involves international collaboration.