Molecular Simulation Study of Wetting at Rough Surfaces

粗糙表面润湿的分子模拟研究

• 批准号: 0828979
• 负责人: Jeffrey Errington
• 金额: $ 20万
• 依托单位: SUNY at Buffalo
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0828979&HistoricalAwards=false
• 关键词: Molecular; Simulation; Study; Wetting; Rough

CBET-0828979ErringtonIntellectual MeritIn a wide range of both naturally occurring phenomena and industrial processes fluids interact with solid substrates. Such fluids exhibit a rich variety of behavior that is distinct from that observed for bulk fluids. The response of a fluid at a surface depends qualitatively upon the relative strengths and ranges of the fluid-fluid and fluid-substrate interactions and the structural characteristics of the substrate. It is the latter of these influences that we focus on here. Specifically, this project will examine the effect of nanoscale substrate roughness and curvature on wetting behavior. Our proposed studies are motivated by recent efforts that employ tunable nanostructured substrate features to modify and control the wetting behavior of a system. Examples include the use of oxygen-plasma treatment to produce polymer surface topographies with periodicity in the 50-300 nm range, the construction of surfaces with aligned carbon nanotube arrays, and the use of silicon nanowires with 20-50 nm diameters to produce fractally rough surfaces.The project proposes two molecular simulation studies that will both complement recent experimental work and advance fundamental knowledge with respect to the wetting behavior of fluids on heterogeneous and/or curved surfaces. Three model fluids will be utilized in this work: an atomistic Lennard-Jones fluid, water, and n-alkane chains. In our first general study we will examine the interfacial properties of fluids at substrates characterized by topographies with a period and amplitude in the 1-10 nm range. This effort will enable one to describe the influence of regular roughness at a length scale that is difficult to probe experimentally. To accomplish this task, the investigators will employ a model that enables us to systematically vary the relative amplitude, length scale, and shape of substrate features exposed to a fluid. Recently-developed simulation methodologies will be used to quantitatively probe how these nanoscale features influence important interfacial properties, including the contact angle, solid-vapor and solid-liquid interfacial tensions, and the line tension, as well as the order of the wetting transition. In the second general stud, they will probe the role of substrate curvature on wetting behavior. A number of recent strategies for controlling the contact angle of a droplet involve the exposure of a fluid to a porous assembly of cylindrical objectives (e.g. carbon nanotubes, silicon nanowires) with diameters on the order of 30-100 fluid molecular diameters. At the molecular level fluid particles interact with highly curved substrates. Density functional calculations with simple systems suggest that this degree of curvature has a significant impact on wetting properties. Given that the diameters of these cylindrical objects can often be controlled, quantitative knowledge of the extent to which curvature influences wetting will prove useful in the design of nanostructured substrates. Within this proposal, the investigators describe a means to quantitatively probe the interfacial properties of fluids at cylindrical objects with diameters spanning from a few to thousands of fluid molecular diameters.Broader ImpactDevelopment of a deeper fundamental understanding of the behavior of fluids in the presence of a surface would have a profound influence on the ability of scientists and engineers to design novel technologies and harness the unique features of natural systems. The results that emerge from this study will have broad impact on numerous scientific disciplines and industrial applications. Examples that illustrate the need for knowledge of how a fluid interacts with a surface are numerous, and include the design of water-repellent and stain-resistant fabrics, friction-reducing surfaces, sensors, medical implants, and nanoscale optofluidic devices. On the education front, this project will impact students at the elementary, undergraduate, and graduate levels. At the university level, students will be trained in the areas of surface thermodynamics, statistical mechanics, and computer simulation. The PI will actively recruit undergraduate students to participate in the project proposed here. Also, the PI will continue an outreach program in which he annually visits 5th grade classrooms at Big Tree Elementary School.

CBET-0828979 Errington智力优势在广泛的自然现象和工业过程中，流体与固体基质相互作用。这种流体表现出丰富多样的行为，这是不同于所观察到的体相流体。流体在表面处的响应定性地取决于流体-流体和流体-基底相互作用的相对强度和范围以及基底的结构特性。我们在这里重点关注的是这些影响中的后一种。具体来说，这个项目将研究纳米级基板粗糙度和曲率对润湿行为的影响。我们提出的研究的动机是最近的努力，采用可调的纳米结构基板功能，修改和控制系统的润湿行为。实例包括使用氧等离子体处理以产生具有50-300 nm范围内的周期性的聚合物表面形貌，具有对齐的碳纳米管阵列的表面的构造，和使用硅纳米线与20-该项目提出了两个分子模拟研究，这两个研究将补充最近的实验工作，并在以下方面推进基础知识：涉及流体在非均匀和/或弯曲表面上的润湿行为。在这项工作中将使用三种模型流体：原子Lennard-Jones流体，水和正烷烃链。在我们的第一个一般性的研究中，我们将研究在基板上的流体的界面特性，其特征在于在1-10 nm范围内的周期和振幅的地形。这一努力将使人们能够描述的影响，规则的粗糙度在一个长度尺度，这是很难探测实验。为了完成这项任务，研究人员将采用一种模型，使我们能够系统地改变暴露于流体的基底特征的相对振幅、长度尺度和形状。最近开发的模拟方法将被用来定量探测这些纳米尺度的功能如何影响重要的界面性质，包括接触角，固-气和固-液界面张力，和线张力，以及润湿过渡的顺序。在第二个一般研究中，他们将探讨基板曲率对润湿行为的作用。用于控制液滴的接触角的许多最新策略涉及将流体暴露于直径在30-100流体分子直径量级的圆柱形物镜（例如碳纳米管、硅纳米线）的多孔组件。在分子水平上，流体颗粒与高度弯曲的基底相互作用。密度泛函计算与简单的系统表明，这种程度的曲率有显着的润湿性能的影响。鉴于这些圆柱形物体的直径通常可以控制，曲率影响润湿的程度的定量知识将证明在纳米结构基底的设计中是有用的。在这一提议中，研究人员描述了一种定量探测流体在直径从几个到几千个流体分子直径的圆柱形物体上的界面性质的方法。更广泛的影响对存在表面的流体行为的更深入的基本理解的发展将对科学家和工程师设计新技术和利用独特的技术的能力产生深远的影响。自然系统的特征。这项研究的结果将对许多科学学科和工业应用产生广泛的影响。说明需要了解流体如何与表面相互作用的例子很多，包括防水和防污织物的设计，减少摩擦的表面，传感器，医疗植入物和纳米级光流体设备。在教育方面，该项目将影响小学、本科和研究生各级的学生。在大学一级，学生将接受表面热力学，统计力学和计算机模拟领域的培训。PI将积极招募本科生参与此处提出的项目。此外，PI将继续一个外展计划，他每年访问大树小学五年级的教室。