CAREER:Collective hydrodynamics of confined drops in microfluidic parking networks

职业：微流体停车网络中受限液滴的集体流体动力学

• 批准号: 1150836
• 负责人: Siva Vanapalli
• 金额: $ 40万
• 依托单位: Texas Tech University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-01 至 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1150836&HistoricalAwards=false
• 关键词: CAREER; Collective; hydrodynamics; confined; drops

1150836PI: VanapalliCurrent high-throughput screening (HTS) methods use robotic actuators for dispensing and diluting fluids in microliter-scale multi-well plates. This approach requires significant investment and imposes constraints on reducing the fluid volumes due to evaporation. Microfluidic arrays of immobilized drops could emerge as an inexpensive and powerful alternative to multi-well plate screening. However, the technical challenge in generating these static drop arrays (SDAs) is to develop a means to (i) array drops of tunable volume and (ii) vary the reagent concentration from drop to drop in the array. Despite recent progress, current microfluidic devices are incapable of manipulating individual drop concentration and varying the volume in the static array. The field is ripe for breakthroughs and if the challenge is met the benefits are enormous ? low cost; reduced fluid volumes; capability to monitor many reactions in drops simultaneously; and ability to further manipulate drops as the position is indexed in the array.To address this challenge, the PI proposes to investigate the dynamics of trains of confined drops and/or long plugs in a special class of fluidic networks called microfluidic parking networks (MPNs). MPNs typically consist of a repeated sequence of loops, with each loop containing a fluidic trap to park (i.e. immobilize) drops. Preliminary exploration in just a small region of the control parameter space yielded a series of unanticipated and astonishing behaviors driven by collective hydrodynamic resistive interactions in the network. Sub-classes of collective behavior involving drop parking, break-up, and coalescence led to the generation of SDAs with tuneable volumes as well as with variation in reagent concentration from drop-to-drop. To harness the full potential and autonomous control offered by the preliminary observations, the PI proposes a comprehensive investigation of the collective hydrodynamics of drops in MPNs, than is currently available. The investigation will focus on (i) coordinated experimental and modeling efforts to predict the spatiotemporal dynamics of drops in MPNs that drive many of the collective behaviors we observed. New tools involving drop-on-demand generators will be integrated into MPNs, to vary the control parameters to map the full phase space of collective dynamics (ii) providing a complete picture of drop/plug break-up in MPNs, by characterizing the fragmentation dynamics to control the size of drop relative to trap. This data when combined with a novel strategy to measure pressure variations during break-up will enable rigorous confrontation of existing models of drop break-up at bifurcations; and (iii) controlling the coalescence and material exchange between parked and moving drops, by probing the factors that regulate film drainage, and passive tracer transport and mixing when drops fuse. The proposed fundamental investigations will enable the development of inexpensive SDAs with sophisticated capabilities. This work is poised to deliver a true nanoliter-scale analog of the multi-well plate with the enormous simplification that dilutions and mixing are carried out passively, thus solving a long-standing challenge. Replacing a room full of robots with these penny-sized devices will tremendously benefit HTS methods in biology and material science. The CAREER project will also provide interdisciplinary training for students in the cutting-edge areas of microfluidics, multiphase flows, microfabrication and nonlinear dynamics. Graphic modules of droplet traffic and parking will be developed for active learning, where students will design their own network topologies and conduct original analysis. These modules will be integrated into an elective course on microfluidics and the core courses. Outreach activities will be developed for middle school girls on the theme "Bubbles on Chips" in which students will mold devices containing a street map of Lubbock and study bubble traffic to identify the exits that bubbles choose.

1150836 PI：Vanapalli目前的高通量筛选（HTS）方法使用机器人致动器在微升规模的多孔板中分配和稀释流体。这种方法需要大量的投资，并且由于蒸发而对减少流体体积施加了限制。固定液滴的微流控阵列可能成为多孔板筛选的廉价且强大的替代方案。然而，产生这些静态液滴阵列（SDA）的技术挑战是开发一种手段来（i）阵列可调体积的液滴和（ii）在阵列中液滴之间改变试剂浓度。尽管最近取得了进展，但目前的微流体装置不能操纵单个液滴浓度并改变静态阵列中的体积。这个领域的突破已经成熟，如果挑战得到满足，好处是巨大的？成本低;减少液体体积;为了应对这一挑战，PI提出研究一类特殊的流体网络中的受限液滴和/或长堵塞物的动力学，这类流体网络被称为微流体停放网络（MPN）。MPN通常由重复的环序列组成，每个环包含流体捕集器以停放（即，阻挡）液滴。在控制参数空间的一个小区域内进行的初步探索产生了一系列意想不到的惊人行为，这些行为是由网络中的集体流体动力学阻力相互作用驱动的。涉及液滴停放、破裂和聚结的集体行为的子类导致具有可调体积以及试剂浓度从液滴到液滴变化的SDA的产生。为了充分利用初步观察所提供的潜力和自主控制，PI提出了对MPN中液滴的集体流体动力学进行全面调查，而不是目前可用的。调查将集中在（i）协调实验和建模工作，以预测MPN中的液滴的时空动态，这些液滴驱动了我们观察到的许多集体行为。涉及按需滴发电机的新工具将被集成到MPN中，以改变控制参数来映射集体动态的全相空间（ii）通过表征碎片动态来控制相对于陷阱的液滴大小，从而提供MPN中液滴/插塞破裂的全貌。这一数据时，结合一种新的策略来测量压力的变化，在分裂过程中，将使严格的对抗现有的模型，滴分裂在分叉处;和（iii）控制停放和移动的滴之间的聚结和材料交换，通过探测的因素，调节膜排水，和被动示踪剂运输和混合时，滴融合。拟议的基础研究将使廉价的SDA的发展与先进的能力。这项工作准备提供一个真正的纳升级模拟多孔板，极大地简化了稀释和混合是被动进行的，从而解决了一个长期存在的挑战。用这些便士大小的设备取代一个装满机器人的房间将极大地有利于生物学和材料科学中的HTS方法。CAREER项目还将为学生提供微流体，多相流，微加工和非线性动力学等前沿领域的跨学科培训。将开发液滴流量和停车的图形模块用于主动学习，学生将设计自己的网络拓扑结构并进行原始分析。这些模块将被整合到微流体选修课程和核心课程。将为中学女生开展主题为“芯片上的气泡”的外联活动，学生们将制作含有拉伯克街道地图的装置，并研究气泡交通，以确定气泡选择的出口。