Exploring the Physical Limits of Structural Superlubricity

这笔赠款将专注于“结构性超润滑性”，这是一种特殊的现象，即两个物体之间的摩擦几乎为零，而不需要使用任何润滑剂。摩擦是机械系统和过程中有用能量损失的主要原因，对国家能源需求有巨大影响。事实上，最近的估计表明，与摩擦相关的经济损失可能高达美国等发达国家国内生产总值的几个百分点。为减少摩擦而设计的新方法对节约有用能源以及经济和环境可持续性具有重要影响。结构超润滑性就是这样一种方法，最近已经在实验中证明了这种方法适用于微观接触。这项研究项目将从运动速度、工作温度和接触尺寸方面探索结构超润滑性的物理极限，以确定这一想法是否可以用于在具有实际意义的机械系统中建立超低摩擦滑动。该项目具有显著的多样性，因为它将在加州大学默塞德分校进行，这是一家拉美裔服务机构，许多学生是第一代学生。除了这些研究工作外，还将针对社会经济服务不足的圣华金河谷地区的K-12学生开展外联活动。该项目的主要目标是从根本上了解结构超润滑性的物理极限，即其对温度和滑动速度等运行条件变化的稳健性，以及超低摩擦状态可以保持的长度范围。为了实现这一目标，将进行基于原子力显微镜的操纵实验，其中金片将在原子平面石墨基板上横向移动，相关摩擦力将被高精度记录下来。实验将在不同的温度、滑动速度和尺寸接近微米的薄片上进行。所获得的结果将为关于结构超润滑性物理限制的新理论提供重要的实验数据。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This grant will focus on “structural superlubricity”, a peculiar phenomenon where friction between two objects nearly vanishes, without the use of any lubricants. Friction is the leading cause of useful energy loss in mechanical systems and processes, with an enormous impact on national energy demand. In fact, recent estimates indicate that economic losses associated with friction can amount up to a few percent of the gross domestic product of a developed nation such as the USA. New methods devised to mitigate friction have important implications for the conservation of useful energy, as well as economic and environmental sustainability. Structural superlubricity is one such method, which has been recently experimentally demonstrated for microscopic contacts. This research project will explore the physical limits of structural superlubricity in terms of speed of motion, operation temperature, and contact size, to determine if the idea can be employed to establish ultra-low friction sliding in mechanical systems of practical relevance. The project has a significant diversity component, as it will be conducted at UC Merced, a Hispanic Serving Institution where many students are first-generation. The research efforts will be additionally complemented by outreach activities aimed at K-12 students in the socio-economically underserved region of San Joaquin Valley. The overarching objective of the project is to form a fundamental understanding of the physical limits of structural superlubricity, in terms of its robustness against changes in operating conditions such as temperature and sliding speed, as well as the length scale up to which the ultra-low friction state can be preserved. To achieve this objective, manipulation experiments based on atomic force microscopy will be performed, whereby gold flakes will be laterally moved on top of atomically flat graphite substrates and the associated friction forces will be recorded with high precision. Experiments will be performed at different temperatures, sliding speeds, and on flakes of sizes approaching the micrometer regime. The obtained results will provide crucial experimental data for the still nascent theories about the physical limitations of structural superlubricity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.