Controlling Microscale Tipstreaming for Sustained Formation of Nanoscale Droplet Reactors

提案编号：0730727主要研究者：Anna， Shelley隶属机构：卡内基梅隆大学提案标题：控制尖端流的纳米级液滴反应器的持续形成提议的工作目标是将一个众所周知的流体力学现象纳入一个流动聚焦微流体装置。这种现象，即尖端流，将允许在内部尺寸大得多（几十微米和几百微米）的微流体装置中形成亚微米级的液滴。作为这项工作的一部分，我们将证明小反应器（液滴）是控制和研究纳米颗粒合成反应的理想选择。该项目的成功完成需要满足三个目标：(1)量化尖端流背后的物理化学力学；(2)利用几何和流体添加剂来实现可控和持续的尖端流；(3)在尖端流产生的纳米反应器中合成金属纳米颗粒。目前在pi实验室进行的研究提供了完成拟议工作所需的实验和分析专业知识。智力优势：两个重要的问题将在拟议的工作中解决：控制界面主导的流体力学现象，以及控制纳米颗粒的生长。我们将发展基本原理和分析模型，以控制微流体装置的尖端流。该模型将为在微流体装置中形成单分散亚微米液滴的方法提供基础，这些微流体装置是通过低成本的技术（如软光刻）制造的。利用和控制亚微米液滴形成过程的能力将为微反应器的开发和定制乳剂的设计开辟新的途径。所获得的知识不仅与这里使用的流动聚焦几何有关，而且与形成亚微米液滴有关，用作形成纳米颗粒的微反应器；我们认为这些小尺寸将为金属纳米颗粒的生长提供一个良好的控制环境。这项工作将使我们能够验证反应器体积均匀性对纳米颗粒质量的影响。该项目将产生一种能够正确研究纳米颗粒生长和发育本质的设备。更广泛的影响：提出的工作将为微流体系统的发展提供一个重要的工具，即能够产生比设备小几个数量级的结构。通过将微流控装置的鲁棒流动控制与低雷诺数液滴动力学的精度相结合，可以在易于制造尺寸的器件中形成亚微米级液滴。这将为不断发展的微流体和“芯片实验室”技术领域带来新的局面。通过pi参与校园教育和外展活动的良好记录，拟议的研究将产生广泛的教育影响。PI和co-I致力于跨学科研究；在两位调查员之间，我们在CMU的五个部门和两个不同的学院（机械工程）中有任命。化学工程，材料科学与工程；（化学和物理）。拟议的项目将真正实现协同增效，两家私人投资机构都将作出重大贡献。专业知识和密切合作的明确必要性。参与该项目的研究生和本科生需要与两个研究小组密切合作；这种互动的好处已经在两位目前共同指导的学生身上得到了证明。过去两年，两间私人顾问一直举行联合小组会议，以加强教育，并让学生接触到互补的思想和技巧；这个项目将从现有的协同作用中发展。这项工作的微流体组成部分的高度可视化性质将允许容易地推断到所有级别的外展活动。我们还将为现有的推广项目开发模块，以消除与“纳米技术”一词相关的一些常见误解。这些模块将适合读者，它们将解决这样一个问题，即即使是学术界以外受过教育的科学家和工程师也对纳米尺度过程（长度和时间）缺乏概念。

Proposal Number: 0730727 Principal Investigators: Anna, Shelley Affiliation: Carnegie Mellon University Proposal Title: Controlling Tipstreaming for Sustained Formation of Nanoscale Droplet Reactors The goal of the proposed work is to incorporate a well-known fluid mechanical phenomenon into a flow-focusing microfluidic device. The phenomenon, tipstreaming, will allow submicron droplets to be formed in microfluidic devices which have much larger internal dimensions (tens and hundreds of microns). As part of this work, we will demonstrate that small reactors (droplets) are ideal for controlling and studying nanoparticle synthesis reactions. Successful completion of the project will require meeting three objectives: (1) quantifying the physicochemical mechanics underlying tipstreaming, (2) exploiting geometry and fluid additives to achieve controllable and sustained tipstreaming, and (3) synthesis of metal nanoparticles within tipstreaming-generated nanoreactors. Current research being performed in the PIs laboratories provides the experimental and analytical expertise needed to complete the proposed work. Intellectual Merit: Two important problems will be tackled in the proposed work: control of an interface-dominated fluid mechanics phenomenon, and control of nanoparticle growth. We will develop fundamental principles and analytical models to control tipstreaming in a microfluidic device. This model will provide the basis for a method to form monodisperse submicron droplets in microfluidic devices that are fabricated via cost effective techniques like soft lithography. The ability to harness and control the process for submicron droplet formation will open new avenues for microreactor development and for the design of custom emulsions. The knowledge gained will be pertinent not only to the flow-focusing geometry utilized here, but is to form submicron droplets for use as microreactors in the formation of nanoparticles; we argue that these small dimensions will provide a well-controlled environment for growing metal nanoparticles. This work will enable us to verify the impact of reactor volume homogeneity on nanoparticle quality. This project will result in a device capable of properly investigating the nature of nanoparticle growth and development. Broader Impact: The proposed work will contribute an important tool to the development of microfluidic systems, namely the ability to generate structures orders of magnitude smaller than the device. By combining robust flow control in microfluidic devices with the precision of low Reynolds number droplet dynamics, submicron droplets can be formed in devices with easily fabricated dimensions. This will add a new regime to the growing field of microfluidic and 'lab-on-a-chip' technology. The proposed research will have broad educational impact through the strong records of both PIs of involvement in educational and outreach activities on campus. The PI and co-I are committed to interdisciplinary research; between the two Investigators, we have appointments in five departments and two different colleges at CMU (Mechanical Eng., Chemical Eng., Materials Science & Eng., Chemistry and Physics). The proposed project will be truly synergistic, with significant contributions coming from both PIs? expertise and a clear necessity for close collaboration. Graduate and undergraduate students involved in the project will need to work closely with both research groups; the benefit of this interaction has already been demonstrated with two current co-advised students. The two PIs have been holding joint group meetings for the last two years to enhance the education and exposure of students to complimentary ideas and techniques; this project will grow from this existing synergy. The highly visual nature of the microfluidics component of this work will allow for easy extrapolation to outreach activities at all levels. We will also develop modules for existing outreach programs to dispel some of the common misconceptions associated with the term 'nanotechnology'. These module(s), which will be made audience-appropriate, will address the issue that even educated scientists and engineers outside of academia have little concept of the scales (length and time) involved in nanoscale processes.