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.

国家科学基金会 - 化学与运输系统部颗粒与多相过程计划（1415）提案编号：0651035原理研究人员：Stebe，Kathleenavefitiation：Johns Hopkins University -Propopals标题：降落脱离模式：微流体设备设备的固有机器人的序列序列序列序列的序列序列序列序列化，该工具是序列化的。细胞碎片，材料制造的试剂等。单个滴剂可以最大程度地减少交叉污染，并提供小的“反应器”，可以在其中进行测定或可以进行产品。滴通常是在存在表面活性剂的情况下形成的，以防止脆弱的试剂（例如蛋白质）的吸附，并减少产生落水相位界面所需的工作。在存在表面活性剂的情况下，可以通过简单地调整液滴和连续流体的相对流速来形成各种液滴。表面活性剂可能在确定降落脱离的状态中起着重要作用。但是，这尚未以定量的方式以表面活性剂的特征性表面作用。吸附 - 吸附受控的表面活性剂，扩散控制的表面活性剂和混合动力扩散受控的表面活性剂与微流体脱落相关的流场中。这个问题自然出现了 - 为什么研究所有三个限制？此外，您如何知道哪个限制适用，如何取决于表面活性剂相关的热力学或动力学参数？最后，在微流体设备中采用表面活性剂质量通量的合适模型是什么？这项工作的重点是在数字和实验中解决这些问题。我们打算确定散装扩散通量和吸附/解吸动力通量的相对重要性，这是滴度长度尺度的函数。我们假设动力学应在与微流体有关的长度尺度上占主导地位。如果可以建立这一点，这将大大简化对十微米及以下长度尺度的滴动力学分析。我们建议使用表面活性剂热力学和运输动力学常数进行表面表面活性剂的表面活性剂进行实验，以与我们的数值预测进行比较。 （表面活性剂将以吊坠分析为特征，其中PI具有丰富的经验。BoaderImplassmultiphase Lab-on-A-A-Chip设备几乎总是包含故意添加的表面活性剂，以减少产生掉落所需的工作。它们通常会使用滴剂来进行序列的序列（例如，蛋白质，肽，eptertions，efterts extress）是有效的。配方，注入模式和脱离条件。在过去的12年中，已经导演了24多个这样的学生。在这些学生中，有9名是女性，其中3名是非裔美国人。这些学生来自各种渠道，包括在JHU招收的有兴趣的大学生以及Jhumrsec-Reu和高中宣传计划。经常邀请PI在外展活动中发表演讲，例如Whiting School Engineering Open House，或为才华横溢的青年中心的演讲，以吸引学生进入科学和工程领域。