近日，清华大学的郑泉水&马明及其研究团队取得一项新进展。经过不懈努力，他们揭示电场对微尺度结构超润滑石墨/金接触摩擦的反常影响。相关研究成果已于2024年1月25日在国际知名学术期刊《国家科学评论》上发表。

在施加电压的情况下，该研究团队在原子平坦的金表面上放置了微尺度石墨片。他们观察到，仅取决于石墨片的边缘是否与金衬底接触，摩擦现象表现出两种相反的趋势。当石墨片与金衬底接触时，随着电压的增加，摩擦力也随之增加；相反，当石墨片不与金衬底接触时，摩擦力会减小。值得注意的是，当电压关闭时，摩擦力会迅速恢复到原来的水平，表明没有发生磨损。

通过大气控制和分子动力学模拟，研究人员揭示了界面水分子和边缘水分子的不同作用。这一实验结果表明，结构超润滑在电场下具有显著的可调谐和鲁棒的摩擦特性。这不仅为滑动电触点的基础研究提供了理想的实验系统，也为需要可调谐摩擦的新型器件提供了理想的系统。

据悉，载流摩擦特性对滑动电触点的性能具有重要影响，而滑动电触点在许多电机和设备中发挥着关键作用。然而，这些特性受到多种因素的影响，包括材料表面质量、化学反应和大气环境等，综合考量这些因素是研究人员面临的一项挑战。结构超润滑（SSL）是一种理想实验系统，可以在接触的固体表面之间实现几乎零摩擦和无磨损的状态。

附：英文原文

Title: The anomalous effect of electric field on friction for microscale structural superlubric graphite/Au contact

Author: Wang, Yelingyi, Wang, Jin, Wu, Tielin, Chen, Weipeng, Peng, Deli, Wu, Zhanghui, Ma, Ming, Zheng, Quanshui

Issue&Volume: 2024-01-25

Abstract: The current-carrying friction characteristics are crucial for the performance of sliding electrical contact, which plays crucial roles in numerous electrical machines and devices. However, these characteristics are influenced by multiple factors such as material surface quality, chemical reactions, and atmospheric environment, leading to the challenge for researchers to comprehensively considering these impacts. Structural superlubricity (SSL), a state of nearly zero friction and no wear between contact solid surfaces, provides an ideal experimental system for these studies. Here, with microscale graphite flake on atomic-flattened Au surface under applied voltages, we observed two opposite friction phenomena, depending only on whether the edge of graphite flake was in contact with the Au substrate. When in contact the friction force would increase with an increasing voltage, otherwise, the friction force would decrease. Notably, when the voltage was turned off, the friction force would be quickly recovered to its original level, indicating the absence of wear. Through atmosphere control and molecular dynamics simulations, we revealed the mechanism to be the different roles played by the water molecules confined at the interface or adsorbed near the edges. Our experimental results demonstrate the remarkable tunable and robust frictional properties of SSL under an electrical field, providing an ideal system not only for the fundamental research of sliding electrical contacts, but also novel devices which demand tunable frictions.

DOI: 10.1093/nsr/nwae019

Source: https://dx.doi.org/10.1093/nsr/nwae019