Drop detachment modes in microfluidics devices

微流体装置中的液滴分离模式

• 批准号: 0651035
• 负责人: Kathleen Stebe
• 金额: $ 20万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0651035&HistoricalAwards=false
• 关键词: Drop; detachment; modes; microfluidics; devices

National Science Foundation - Division of Chemical &Transport Systems Particulate & Multiphase Processes Program (1415)Proposal Number: 0651035Principal Investigators: Stebe, KathleenAffiliation: Johns Hopkins UniversityProposal Title: Drop detachment modes in microfluidics devicesIntellectual MeritDrops surrounded by a continuous phase are formed in microfluidics devices to sequester proteins, lipids, cellular fragments, reagents for materials manufacture, etc. The individual drops allow cross contamination to be minimized, and provide small "reactors" in which assays can be performed or products can be made. The drops are often formed in the presence of surfactants, either to prevent the adsorption of fragile reagents (e.g. proteins) and to reduce the work required to produce the drop-continuous phase interface. In the presence of surfactants, a wide range of drops can be formed in a flow focusing device by simply tuning the relative flow rates of the drop and continuous fluids. Surfactants likely play a strong role in determining the regime of drop detachment. However, this has not been established in a quantitative fashion with well characterized surfactants.We intend to study drop formation and detachment in a flow focusing device for three regimes of surfactant mass transfer; adsorption-desorption controlled surfactants, diffusion controlled surfactants and mixed kinetic-diffusion controlled surfactants in flow fields relevant to drop detachment in microfluidics. The question naturally arises- why study all three limits? Furthermore, how do you know which limit applies, and how does it depend on the surfactant related thermodynamic or kinetic parameters? Finally, what is the appropriate model to adopt for the mass flux of surfactant in a microfluidics device? A major focus of this work is to address these questions in numerics and experiment. We intend to establish the relative importance of bulk diffusion flux and adsorption/desorption kinetic fluxes as a function of drop length scale. We hypothesize that kinetics should dominate on length scales relevant to microfluidics. If this can be established, this would greatly simplify the analysis of drop dynamics in the length scale of ten microns and below. We propose to perform experiments using well characterized surfactants in terms of the surfactant thermodynamics and transport kinetic constants to compare to our numerical predictions. (The surfactants will be characterized by pendant drop analysis, in which the PI has extensive experience.Broader ImpactsMultiphase lab-on-a-chip devices nearly always contain deliberately added surfactant to reduce the work required to produce drops. They typically use drops to sequester reagents (e.g. proteins, peptides and fragments) that are surface active. At present, there are no selection rules to guide the relationship between surfactant formulations, injection modes and detachment conditions. Meanwhile, experimental evidence for the rich behavior of surfactant-laden drops in terms of phase diagrams of break up modes reveal complex behavior with a number of transitions. By developing improved control over these systems, we support expanded use of multiphase flow microfluidics devices for diagnostics, screening and manufacturing.The PI regularly welcomes undergraduate and high school students into her laboratories, and has directed more than 24 such students over the past 12 years. Of these students 9 were women, and 3 were African American. These students have been drawn from various channels, including interested undergraduates enrolled at JHU, and the JHUMRSEC-REU and high school outreach programs. The PI is regularly invited to speak at outreach events, such as the Whiting School Engineering Open House, or presentations for the Center for Talented Youth to draw students into the science and engineering fields.

美国国家科学基金会-化学与工业运输系统颗粒与安培多相工艺计划(1415)提案编号：0651035主要研究人员：Stebe，凯瑟琳附属公司：约翰霍普金斯大学提案标题：微流体设备中的液滴脱离模式智力被连续相包围的液滴在微流体设备中形成，以隔离蛋白质、脂类、细胞碎片、材料制造试剂等。液滴通常是在表面活性剂存在的情况下形成的，要么是为了防止易碎试剂(如蛋白质)的吸附，要么是为了减少产生液滴-连续相界面所需的功。在表面活性剂存在的情况下，通过简单地调节液滴和连续流体的相对流速，就可以在流动聚焦装置中形成大范围的液滴。表面活性剂可能在决定液滴脱离机制中起着重要作用。我们打算在流动聚焦装置中研究与液滴分离相关的三种流动聚焦装置中的液滴形成和分离：吸附-解吸控制的表面活性剂、扩散控制的表面活性剂和混合的动力学-扩散控制的表面活性剂。问题自然产生了--为什么要研究这三个限制呢？此外，您如何知道哪个限制适用，以及它如何依赖于与表面活性剂相关的热力学或动力学参数？最后，对于微流控装置中表面活性剂的质量流量，采用什么模型比较合适？这项工作的一个主要焦点是在数值和实验中解决这些问题。我们打算建立整体扩散通量和吸附/解吸动力学通量作为液滴长度尺度的函数的相对重要性。我们假设动力学应该在与微流体有关的长度尺度上起主导作用。如果能够确定这一点，这将极大地简化十微米及以下长度范围内的液滴动力学分析。我们建议使用表征良好的表面活性剂在表面活性剂热力学和迁移动力学常数方面进行实验，以与我们的数值预测进行比较。(表面活性剂将通过悬浮液滴分析来表征，PI在这方面拥有丰富的经验。宽频影响多相芯片实验室设备几乎总是含有故意添加的表面活性剂，以减少产生液滴所需的功。他们通常使用液滴来隔离具有表面活性的试剂(例如蛋白质、多肽和片段)。目前还没有一个选择规则来指导表面活性剂配方、注入方式和脱附条件之间的关系。同时，根据破裂模式相图，实验证据表明表面活性剂液滴具有丰富的行为，揭示了具有多个转变的复杂行为。通过改进对这些系统的控制，我们支持更多地使用多相流微流控设备进行诊断、筛选和制造。PI经常欢迎本科生和高中生进入她的实验室，并在过去12年中指导了24名以上的学生。在这些学生中，9名是女性，3名是非裔美国人。这些学生来自不同的渠道，包括在JHU注册的感兴趣的本科生，JHUMRSEC-REU和高中外展计划。PI经常被邀请在推广活动中发言，如怀廷学校工程开放日，或青年才华中心的演讲，以吸引学生进入科学和工程领域。