Collaborative Research: Probing the hydrodynamic resistance and traffic of confined droplets in microfluidic networks for the rational design of two-phase fluidic processors

由于微流体科学和工程的快速发展，利用油相中的微小纳升级水滴作为反应容器应用于化学和生命科学的想法正在成为现实。尽管取得了这些进展，但将目前基于液滴的设备转变为能够表征大规模生物复杂性的下一代流体处理器仍然存在根本性的挑战。在实现这种集成两相流体处理器的过程中存在两个科学挑战。首先，微通道中大量受限液滴的传输导致了过高的压降。其次，由于集体流体动力阻力效应，难以控制装置上反应液滴的位置和时间。为了解决这些挑战，需要彻底了解由受限液滴运动引入的水动力阻力。pi将结合实验和建模来量化由于受限液滴及其对系统参数的依赖而产生的水动力阻力。这项工作的新方面包括使用敏感的微流体比较器技术来测量单个液滴水平上的流体动力阻力。将开发实验方法和模型来量化目前未知的端帽、薄膜和角流对矩形微通道中液滴流体动力阻力的贡献，最终目标是实现压降的预测能力，以增强器件性能。该研究将为合理设计具有自主和被动驱动潜力的两相流体处理器提供可能。这项工作还将影响其他依赖于对受限介质中多相流的基本理解的工程领域，如三次采油和燃料电池。该项目的教育部分包括吸引少数民族研究生和本科生进行微流控视觉上引人注目的研究，并提供微流控、微加工、显微镜和数值模拟方面的最先进培训。pi将在各自的机构开展外展活动，例如开展为期一周的实践活动和以“芯片上的泡沫”为主题的讲座。

0932796/0933090 Vanapalli/Wong The notion of using tiny nanoliter-scale water droplets in an oil phase as reaction vessels for applications in chemical and life sciences is turning into a reality due to rapid progress in the science and engineering of microfluidics. Despite such progress, fundamental challenges remain to transform current droplet-based devices to next generation fluidic processors capable of characterizing large-scale biological complexity. Two scientific challenges exist in the realization of such an integrated two-phase fluidic processor. First, the transport of a large number of confined droplets in microchannels leads to prohibitively excess pressure drop. Second, due to collective hydrodynamic resistive effects, it is difficult to control the position and timing of droplets for reactions on a device. To address these challenges requires a thorough understanding of hydrodynamic resistance introduced by the motion of confined droplets. The PIs will combine experiments and modeling to quantify the hydrodynamic resistance due to a confined droplet and its dependence on system parameters. Novel aspects of the work include the use of a sensitive microfluidic comparator technique to measure hydrodynamic resistance at the level of individual droplets. Experimental methods and models will be developed to quantify the currently unknown contribution of end-cap, thin film and corner flows to the hydrodynamic resistance of a droplet in rectangular microchannels, with the ultimate goal of achieving predictive capability of pressure drop for enhanced device performance. This study will enable rational design of two-phase fluidic processors that could be potentially autonomous and passively driven. This work will also impact other engineering areas that rely on fundamental understanding of multiphase flows in confined media such as tertiary oil recovery and fuel cells. Educational component of the project includes drawing minority graduate and undergraduate students to the visually striking research on microfluidics and providing state-of-the-art training in microfluidics, microfabrication, microscopy and numerical modeling. The PIs will pursue outreach activities at their respective institutions such as developing a weeklong hands-on-activities and lectures on the theme "Bubbles on Chips".