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

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。特别注意检查的效果，金属间化合物的形成液滴润湿动力学，接触线的进步，和固-液界面的演变。使用一个多尺度模型，集成了混合相场和任意拉格朗日-欧拉方法在宏观尺度和分子动力学模拟在原子水平上，该项目旨在解决几个基本问题的理解和预测反应润湿：（一）什么是反应润湿的主导驱动力和耗散机制？PI旨在了解相关的驱动力和耗散机制是否可以分为不同的机制，或者它们是否在一个或多个机制中强烈耦合。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整合到宏观移动边界问题中，以研究流动，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向接触线区域提供新材料的机制的影响。金属间化合物的形成和生长的接触线区域上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？将计算流场、温度场和浓度场，以解释它们如何相互作用，从而形成一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率，并将其与基材溶解速率相关联。将探讨固体到液体到固体相变的可能性，并将结果与文献中的实验观察结果进行比较。对反应润湿过程中的耦合反应和润湿动力学的基本理解对于在材料连接中创建更强的键合、更好的薄膜涂层粘附力、用于生物植入物的新型复合材料以及具有可调功能的表面改性的新途径至关重要。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，该领域涉及多组分，多相系统的流动，热/质传递，相变和化学反应。研究生和本科生将在物理学，材料科学，工程和化学的交叉点的跨学科研究领域工作。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就相变的原子模型进行互动。拟议的研究还将为两门研究生课程提供新的课程材料，并通过德雷克塞尔的赫斯荣誉计划和为期六个月的密集研究合作计划支持本科研究人员。通过PI对RET教师和费城学区宾夕法尼亚州东部女童子军的指导，外联活动将扩展到大学预科学生和那些代表性不足的群体。非技术性总结该奖项支持与液滴如何与表面接触和传播有关的理论和计算研究以及教育活动。PI还将包括液体与其在其上铺展的固体基质的反应。这在许多技术应用中起着重要作用，包括材料加工和连接、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改性。材料的最新进展是结构化到比人类头发小一万倍的规模，这需要更高的精度来控制这种反应性润湿过程。尽管其重要性，反应润湿仍然是一个知之甚少的过程。PI将进行计算机模拟，旨在解决理解反应润湿和使用计算机模拟过程的能力的基本问题。模型预测将根据实验观察进行验证。该项目在材料加工和连接、薄膜涂层和液滴操作过程中非常重要。该过程涉及至少三个界面，这些界面通常远离平衡的平衡状态，并且在用于能量转换和存储、生物植入物、微机电设备和电子封装的先进材料的合成和加工中发挥重要作用。PI研究的复杂多相系统发生在许多过程工业中，以及自然界和生物体中。因此，这项工作将有助于建立可用于广泛应用的研究方法。该项目的跨学科性质，在物理学，材料科学，工程学和化学的交叉点，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，利用流体动力学，热/质传递和材料科学的跨学科工具，研究跨长度尺度材料加工中的传输现象。拟议的研究还将为两门研究生课程提供新的教材。研究产品将部分通过开放源码计算机代码包传播。社区外展计划将扩展到费城市中心的K-12教师和学生，其中约80%是少数民族学生。

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.