Dynamics of capillary threads and high-viscosity droplets in microfluidic systems

0932925古巴该奖项是根据2009年美国复苏和再投资法（公法111-5）资助的。该研究描述了一套集成的活动，用于在小规模的不混相低粘性流体护套中精确操作高粘度流体。微流体学是一个快速发展的领域，但对大粘度差的多流体流动的研究仍然有限。然而，许多工业和生物流体，如重油和溶剂，表现出广泛不同的粘度。他们的小规模操作将为芯片实验室设备提供新的功能。透明的高压微型装置将显示与小流体通道中高粘度材料的润滑有关的机制。计划进行两项调查。第一部分研究了分散-收敛微流体室中粘性岩心环流的动力学。细长粘性结构在发散微通道中的屈曲不稳定性将用于控制螺纹形态和诱导断裂。研究了线与微通道壁之间的薄插层膜的稳定性，以研究波纹的形成和强制润湿现象。第二项研究研究了高粘度液滴在腔室和物理化学分层。高粘度液滴之间的流体动力耦合和聚结将在拉伸几何中进行研究。PI将研究通过诱导低粘度和高粘度液滴之间的聚结来增强微混合的可能性。最后，在横流中注入物理化学分层将形成粘性液滴。该系统将提供一个简单的多步流反应器模型。本研究计划将在一个相对未开发的微尺度多流体流动区域中描述新的流体行为。特别是，利用拉伸微观几何来改变对流时间尺度，可以操纵复杂的现象，如高粘度微观结构的屈曲、润湿、聚并、破裂和松弛。简单的流动几何图形将阐明这些现象之间的相互关系。本研究将整合系统的实验方法与数值模拟和理论预测，以协助下一代微流体装置的发展。这项工作结合了对大量学生的研究和培训，包括代表性不足的高中生、本科生和研究生。教育活动的中心目标是吸引和培养理工科学生。本项目的一个重要方面是设计方法来控制高粘性油和溶剂（如乙醇）之间的新型连续乳化过程。因此，将开发的技术专长可能会为制造更高效的发动机、提高石油采收率以及开发用于生物燃料生产的连续多步流反应器提供颠覆性的进步。

0932925CubaudThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This study describes an integrated suite of activities for the precise manipulation of high-viscosity fluids in a sheath of immiscible less viscous fluids at the small-scale. Microfluidics is a fast developing field, yet investigations of multi-fluids flows with large viscosity contrasts have remained limited. Numerous industrial and biological fluids such as heavy oils and solvents, however, exhibit widely varying viscosities. Their manipulation at the small-scale would provide new capabilities for lab-on-chip devices. Transparent high-pressure microdevices will display the mechanisms associated with the lubrication of high-viscosity materials in small fluidic passages. Two investigations are planned. The first pursues the dynamics of viscous core-annular flows in diverging-converging microfluidic chambers. Buckling instabilities of slender viscous structures in diverging microchannels will be exploited to control the threads morphology and induce breakup. The stability of thin intercalating films between threads and microchannel walls will be investigated for formation of ripples and forced wetting phenomena. The second investigation studies high-viscosity droplets in chambers and physicochemical stratifications. The hydrodynamic coupling and coalescence between high-viscosity droplets will be examined in extensional geometries. The PI will investigate the possibility to enhance micromixing by inducing coalescence between low- and high-viscosity droplets. Finally, physicochemical stratifications injected in cross-flow will engineer viscous droplets. This system will provide a simple model of multi-step flow reactors. This research program will characterize novel fluid behaviors in a relatively unexplored region of microscale multi-fluid flows. In particular, the alteration of convective time-scales using extensional microgeometries permits the manipulation of complex phenomena such as buckling, wetting, coalescence, breakup, and relaxation of highly-viscosity microstructures. Simple flow geometries will elucidate the interrelation between these phenomena. This study will integrate a systematic experimental approach with numerical simulations and theoretical predictions to aid development of next-generation microfluidic devices. This work combines research and training of a large spectrum of students, including underrepresented, high school, undergraduate, and graduate students. A central objective of the educational activities is to attract and nurture students in the science and engineering fields. An important aspect of this project is to devise methods to control novel continuous emulsification processes between highly viscous oils and solvents, such as ethanol. Thus, the technical expertise that will be developed can potentially provide disruptive advances for making more efficient engines, enhancing oil recovery, and developing continuous multi-step flow reactors for bio-fuel production.