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Mechanics of Nanoscale Single Asperity Contacts in Friction Force Microscopy

摩擦力显微镜中纳米级单粗糙体接触的力学

基本信息

批准号：
EP/F039999/1
负责人：
Graham Leggett
金额：
$ 51.34万
依托单位：
University of Sheffield
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FF039999%2F1
关键词：
Mechanics Nanoscale Single Asperity Contacts

项目摘要

Many new technologies are relying upon nanostructured devices and materials to deliver new properties and improved performance. Many everyday technologies also depend upon the organisation of materials at the nanometre scale. A good illustration of this is the action of hair and fabric conditioners, which rely for their performance on the ability to control the distribution of conditioner molecules at complex, curved surfaces (hair fibres are only 100 micrometres in diameter, and textile fibres may be much smaller) with uniform distribution being required on very small length scales. In all of these areas, there is an urgent need for information about the distribution of molecules at the surface with a resolution of nanometres. However, there are very few ways of doing this. Friction force microscopy (FFM), which uses a sharp tip attached to a flexible microscopic cantilever to measure surface friction, provides one solution to this problem. In addition to providing a means of mapping surface composition, FFM also provides an ideal model system for understanding the types of sliding contacts that occur in new miniaturised technologies such as microelectromechanical devices, where tiny sliding contacts require lubrication but where conventional lubricants fail.The principal difficulty with using FFM to solve these varied problems is that we still lack an adequate understanding of the fundamental principles that underpin its mechanism of operation. In order to obtain quantitative information about surface friction, we must first be able to understand the contact mechanics associated with the tip-sample interaction - the microscopic physical interactions that determine the strength of the frictional interaction. There has been a great deal of debate about this. Some researchers have favoured the use of a very old physical law, Amontons' law, which states simply that the friction force is proportional to the load applied perpendicular to the sample surface. Others have suggested that more complex laws apply. Recent significant progress was made by the applicants, who showed for the first time that not just the strength of the frictional interaction, but also the type of mechanics that applied seemed strongly influenced by the environment in which the FFM experiment was conducted. The objective of this proposal is to build on these preliminary findings, by building a broad understanding of the mechanics of FFM. Such a venture will provide an interpretational framework for the technique that is grounded in solid experimental data. In addition to developing a better understanding of fundamental principles, we also aim to apply the technique to two important classes of materials: organic polymers (polystyrene and polymethylmethacrylate), where the molecular weight determines many of the mechanical properties of the material; and polymer brushes, new materials that are attracting enormous interest because of the potential they offer for control of interfacial interactions such as adhesion. In both cases, FFM may provide a quicker and easier method for exploring molecular structure and properties than other techniques currently available, and it could prove a valuable tool to researchers working on a variety of problems.

许多新技术都依赖于纳米结构的器件和材料来提供新的特性和改进的性能。许多日常技术也依赖于纳米尺度的材料组织。这方面的一个很好的例子是头发和织物调理剂的作用，其性能依赖于控制调理剂分子在复杂弯曲表面（头发纤维的直径仅为100微米，纺织纤维可能小得多）上的分布的能力，在非常小的长度尺度上需要均匀分布。在所有这些领域中，迫切需要有关表面分子分布的信息，其分辨率为纳米。然而，这样做的方法很少。摩擦力显微镜（FFM），它使用一个尖锐的尖端连接到一个灵活的微观悬臂测量表面摩擦，提供了一个解决这个问题。除了提供绘制表面成分的方法外，FFM还提供了一种理想的模型系统，用于了解新的小型化技术（例如微机电设备）中出现的滑动接触类型，在微小的滑动接触需要润滑，而常规润滑剂失效的情况下，使用FFM解决这些不同问题的主要困难在于，我们仍然缺乏对基本原理的充分理解支撑其运作机制的东西。为了获得有关表面摩擦的定量信息，我们必须首先能够理解与针尖-样品相互作用相关的接触力学-决定摩擦相互作用强度的微观物理相互作用。关于这一点有很多争论。一些研究人员倾向于使用一个非常古老的物理定律，即阿蒙顿定律，该定律简单地说，摩擦力与垂直于样品表面施加的载荷成正比。其他人则建议适用更复杂的法律。申请人最近取得了重大进展，他们首次证明，不仅摩擦相互作用的强度，而且所应用的力学类型似乎都受到FFM实验进行环境的强烈影响。这项建议的目的是在这些初步调查结果的基础上，对实况调查的机制有一个广泛的了解。这样的冒险将为基于坚实实验数据的技术提供一个解释框架。除了更好地理解基本原理外，我们还旨在将该技术应用于两类重要的材料：有机聚合物（聚苯乙烯和聚甲基丙烯酸甲酯），其中分子量决定了材料的许多机械性能;和聚合物刷，新材料吸引了巨大的兴趣，因为它们提供了控制界面相互作用的潜力，如粘附力。在这两种情况下，FFM可以提供一个更快，更容易的方法来探索分子的结构和性能比目前可用的其他技术，它可以证明是一个有价值的工具，研究人员对各种问题的工作。