Multi-scale Study of Coupled Reaction and Wetting in Droplet Spreading

技术总结该奖项支持与液滴扩散中的耦合反应和润湿动力学相关的理论和计算研究以及教育活动。重点研究了金属间化合物的形成对液滴润湿动力学、接触线推进和固液界面演化的影响。利用一个多尺度模型，在宏观尺度上集成了混合相场和任意拉格朗日-欧拉方法，并在原子水平上进行了分子动力学模拟，该项目试图解决在理解和预测反应润湿中的几个基本问题：(I)在反应润湿中，主导驱动力和耗散机制是什么？PI的目的是了解相关的驱动力和消散机制是否可以分为不同的制度，或者它们是否在一个或多个制度中强烈耦合。利用分子动力学模拟的输入，PI将金属间化合物的形成和生长集成到宏观移动边界问题中，以检查流动、物种传输和化学反应之间的耦合机制。(Ii)在新的界面形成过程中，材料是如何输送到接触线的？PI将研究反应和表面合金化对将新材料输送到接触线区域的机制的影响。金属间化合物在接触线区域的形成和生长对液滴润湿动力学的影响将被量化。(Iii)在耦合反应和润湿过程中固-液界面是如何演变的？将计算流动、温度和浓度场，以解释它们如何相互作用以产生特定形状的固-液界面和金属间化合物类型。PI还将量化金属间化合物的生长速度，并将其与衬底溶解速度联系起来。我们将探索固-液-固相变的可能性，并将结果与文献中的实验观察结果进行比较。基本了解反应润湿过程中的偶合反应和润湿动力学对于在材料连接中创建更强的键、提高薄膜涂层的附着力、用于生物植入的新型复合材料以及具有可调功能的表面改性新途径至关重要。这项工作将对材料加工、MEMS制造、电子封装、能量转换和存储以及表面化学等领域产生影响。该项目还将推进一个很大程度上未知的研究领域，涉及具有流动、热/质传递、相变和化学反应的多组分、多相系统。研究生和本科生将接受在物理学、材料科学、工程学和化学交叉学科研究领域工作的培训。与麦克马斯特大学和桑迪亚国家实验室的合作将使PI和她的学生能够与领先的研究小组互动，执行相变的原子建模。这项拟议的研究还将为两门研究生水平的课程提供新的课程材料，并通过Drexel的Hess荣誉计划和为期六个月的密集研究合作计划支持本科生研究人员。通过PI对费城学区的RET教师和宾夕法尼亚州东部的女童子军的指导，外展将扩展到大学预科学生和那些来自代表不足的群体的学生。非技术总结该奖项支持与液滴如何与表面接触和扩散有关的理论和计算研究和教育活动。等电点还将包括液体与其所在的固体基质的反应。这在材料加工和连接、薄膜涂层、可印刷电子制造、多相催化、液滴驱动和操纵以及表面修饰等许多技术应用中都发挥着重要作用。最近在材料方面的进展要求对这种反应性润湿过程的控制有更高的精度，这些材料的结构尺寸小于人类头发的一万倍。尽管反应润湿很重要，但它仍然是一个鲜为人知的过程。PI将进行计算机模拟，旨在解决了解反应润湿和使用计算机模拟过程的能力方面的基本问题。模型预测将与实验观测结果进行验证。该项目在材料加工和连接、薄膜涂层和液滴操纵过程中具有重要意义。该过程包括至少三个通常远离平衡状态的界面，并且在能量转换和存储、生物植入物、微型机电设备和电子封装的先进材料的合成和加工中发挥着重要作用。PI研究的复杂多相系统存在于许多过程工业中，以及自然界和生物体内。因此，这项工作将有助于建立可在广泛的应用中使用的研究方法。该项目的跨学科性质，处于物理、材料科学、工程和化学的交叉点，使其成为学生的一个很好的教育机会。研究生和本科生将接受培训，利用流体力学、热/质传递和材料科学中的交叉学科工具，研究材料加工过程中的传输现象。拟议的研究还将为两门研究生课程提供新的课程材料。研究产品将部分通过开放源码的计算机代码包传播。社区外展计划将扩展到费城市中心的K-12教师和学生，其中大约80%是少数族裔学生。

TECHNICAL SUMMARYThis award supports theoretical and computational research and educational activities related to coupled reaction and wetting dynamics in droplet spreading. Special attention is paid to examine the effect of intermetallic compound formation on drop wetting kinetics, contact line advancement, and the evolution of the solid-liquid interface. Using a multi-scale model that integrates the hybrid phase-field and arbitrary Lagrangian-Eulerian approach at the macroscopic scale and molecular dynamics simulations at the atomistic level, this project seeks to address several fundamental issues in the understanding and prediction of reactive wetting: (i) What are the dominating driving forces and dissipation mechanisms in reactive wetting? The PI aims to understand whether the relevant driving forces and dissipation mechanisms can be separated into distinct regimes or whether they are strongly coupled in one or multiple regimes. Using inputs from molecular dynamics simulations, the PI will integrate the intermetallic compound formation and growth into the macroscopic moving boundary problem to examine the coupling mechanisms among flow, species transport, and chemical reaction.(ii) How is material delivered to the contact line during new interface formation? The PI will examine the effect of reaction and surface alloying on mechanisms that deliver new materials to the contact line region. The effects of intermetallic compound formation and growth in the contact line region on drop wetting kinetics will be quantified.(iii) How does the solid-liquid interface evolve during coupled reaction and wetting? The flow, temperature, and concentration fields will be computed to explain how they interact to result in a certain shape of the solid-liquid interface and types of intermetallic compounds. The PI will also quantify the intermetallic compound growth rate and relate it with the rate of substrate dissolution. The possibility of solid to liquid to solid phase transition will be explored and results will be compared with experimental observations from the literature.Fundamental understanding of coupled reaction and wetting dynamics during reactive wetting is crucial in creating stronger bonds in materials joining, better adhesion for thin film coating, novel composites for bio-implants, and new routes for surface modification with tunable functionalities. This work will have impact on areas ranging from materials processing, MEMS fabrication, electronics packaging, to energy conversion and storage and surface chemistry. This project will also advance a largely uncharted area of research that is concerned with multi-component, multi-phase systems with flow, heat/mass transfer, phase change, and chemical reactions. Graduate and undergraduate students will be trained working in an interdisciplinary research area at the intersection of physics, materials science, engineering, and chemistry. Collaborations with McMaster University and Sandia National Laboratories will enable the PI and her students to interact with leading research groups on performing atomistic modeling of phase transformation. The proposed research will also enable new course materials for two graduate-level courses and support undergraduate researchers via Drexel's Hess Honors program and the six-month intensive research co-op program. Outreach will extend to pre-college students and those from underrepresented groups through PI's mentoring of RET teachers and Girl Scouts of Eastern Pennsylvania from School District of Philadelphia.NONTECHNICAL SUMMARYThis award supports theoretical and computational research and educational activities related to how a droplet makes contact with a surface and spreads. The PI will also include the reaction of the liquid with the solid substrate on which it is spreading. This plays an important role in many technological applications including materials processing and joining, thin film coating, printable electronics fabrication, heterogeneous catalysis, droplet actuation and manipulation, and surface modification. Recent advances in materials that are structured down to a scale some ten thousand times smaller than a human hair require greater precision in the control of this reactive wetting processes. Despite its importance, reactive wetting remains a poorly understood process. The PI will perform computer simulations aimed to address fundamental issues in understanding reactive wetting and the ability to use computers to simulate the process. Model predictions will be validated against experimental observations. This project is important in materials processing and joining, thin film coating, and droplet manipulation processes. The process involves at least three interfaces that are typically away from the balanced state of equilibrium and plays a significant role in synthesis and processing of advanced materials for energy conversion and storage, bio-implants, micro-electro-mechanical devices, and electronics packaging. The complex multi-phase systems studied by the PI occur in numerous process industries, as well as in nature and in living organisms. Thus, this work will help to establish research methodology that can be used in a broad array of applications.The interdisciplinary nature of the project, at the intersection of physics, materials science, engineering, and chemistry, makes it a great educational opportunity for students. Graduate students and undergraduate students will be trained to utilize interdisciplinary tools in fluid dynamics, heat/mass transfer, and materials science to study transport phenomena in materials processing across length scales. The proposed research will also enable new course materials for two graduate-level courses. Research products will be disseminated in part through open-source computer code packages. The community outreach programs will extend to inner-city K-12 teachers and students in Philadelphia with approximately 80% minority students.