Lubricated friction around nanodefects
Lubricated friction around nanodefects
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DOI：
10.1126/sciadv.aaz3673
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发表时间：
2020-04-01
期刊：
影响因子：
13.6
通讯作者：
Voitchovsky, Kislon
中科院分区：
文献类型：
--
作者：
Cafolla, Clodomiro;Foster, William;Voitchovsky, Kislon
纳米流体的润滑特性是无数自然和工业过程的基础。然而，我们目前对润滑摩擦的理解仍然有限，特别是对于表现出纳米级化学和地形缺陷的非理想界面。在这里，我们使用原子力显微镜来探索一种模型润滑剂角鲨烷的平衡和动力学行为，角鲨烷被限制在金刚石尖端和原子步骤附近的石墨之间。我们将界面的高分辨率成像与不同速度和温度下的高度局部剪切测量相结合，得出表面缺陷周围润滑摩擦的定量图像。我们发现缺陷倾向于通过减少其附近稳定分子构型的数量来促进局部分子秩序和增加摩擦力。这种效应是普遍的，可以在数百纳米范围内传播，并且可以通过连接分子细节和中尺度观测的半经验模型进行定量描述。
The lubrication properties of nanoconfined liquids underpin countless natural and industrial processes. However, our current understanding of lubricated friction is still limited, especially for nonideal interfaces exhibiting nanoscale chemical and topographical defects. Here, we use atomic force microscopy to explore the equilibrium and dynamical behavior of a model lubricant, squalane, confined between a diamond tip and graphite in the vicinity of an atomic step. We combine high-resolution imaging of the interface with highly localized shear measurements at different velocities and temperatures to derive a quantitative picture of the lubricated friction around surface defects. We show that defects tend to promote local molecular order and increase friction forces by reducing the number of stable molecular configurations in their immediate vicinity. The effect is general, can propagate over hundreds of nanometers, and can be quantitatively described by a semiempirical model that bridges the molecular details and mesoscale observations.