CAREER:Collective hydrodynamics of confined drops in microfluidic parking networks

目前的高通量筛选（HTS）方法使用机器人执行器在微升规模的多孔板中分配和稀释流体。这种方法需要大量投资，并且由于蒸发而限制了减少流体体积。固定化液滴的微流控阵列可能成为多孔板筛选的一种廉价而强大的替代方法。然而，生成这些静态液滴阵列（SDAs）的技术挑战是开发一种方法来(i)阵列可调节体积的液滴和（ii）改变阵列中每一滴的试剂浓度。尽管最近取得了进展，但目前的微流控装置无法控制单个液滴浓度和改变静态阵列中的体积。该领域取得突破的时机已经成熟，如果迎接挑战，收益将是巨大的。低成本;流体体积减小；能够同时监测液滴中的许多反应；并且可以在数组中索引位置时进一步操作下降。为了应对这一挑战，PI建议研究一种特殊类型的流体网络（称为微流体停放网络（mpn））中受限液滴和/或长塞的动力学。mpn通常由重复的循环序列组成，每个循环包含一个流体陷阱来停放（即固定）液滴。在控制参数空间的一个小区域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集体流体动力阻力相互作用驱动的。集体行为的子类包括滴停车、分裂和聚结，导致sda的产生具有可调节的体积以及滴到滴的试剂浓度变化。为了充分利用初步观测提供的潜力和自主控制，PI建议对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。研究将集中在(i)协调实验和建模工作，以预测驱动我们观察到的许多集体行为的mpn下降的时空动态。包括按需滴入发生器在内的新工具将集成到mpn中，以改变控制参数来绘制集体动力学的完整相空间。（ii）通过表征破碎动力学来控制相对于捕集器的滴入大小，提供mpn中滴入/桥塞破裂的完整图像。当这些数据与一种测量破裂过程中压力变化的新策略相结合时，将能够严格对抗现有的分岔液滴破裂模型；(3)通过探索液滴熔合时调节膜排水、被动示踪剂输送和混合的因素，控制停滴和动滴之间的聚结和物质交换。拟议的基础研究将使开发具有复杂功能的廉价sda成为可能。这项工作将提供一个真正的纳米级多孔板模拟，极大地简化了被动进行稀释和混合的过程，从而解决了一个长期存在的挑战。用这些一分钱大小的设备取代满屋子的机器人，将极大地有利于生物和材料科学中的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。液滴交通和停车的图形模块将开发为主动学习，学生将设计自己的网络拓扑并进行原始分析。这些模块将整合到微流体选修课程和核心课程中。以“薯条上的泡泡”为主题，为中学女生开展拓展活动，学生们将制作包含拉伯克街道地图的设备，并研究泡泡交通，以识别泡泡选择的出口。

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.