The transition from Elasto‐Hydrodynamic to Mixed Regimes in Lubricated Friction of Soft Solid Surfaces
The transition from Elasto‐Hydrodynamic to Mixed Regimes in Lubricated Friction of Soft Solid Surfaces
复制标题
软固体表面润滑摩擦从弹性流体动力学到混合状态的转变
DOI：
10.1002/adma.202211044
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发表时间：
2023
影响因子：
29.4
通讯作者：
Jagota, Anand
中科院分区：
文献类型：
--
作者：
Dong, Hao;Moyle, Nichole;Wu, Haibin;Khripin, Constantine Yuri;Hui, Chung‐Yuen;Jagota, Anand
软材料中的润滑触点在各种工程和自然环境中是常见的，例如轮胎、触觉应用、隐形眼镜和软电子设备的制造。两种主要的机制是弹性流体动力润滑（EHL），其中固体表面被流体膜完全分离，以及混合润滑（ML），其中存在部分固体与固体接触。这些状态之间的过渡控制着可实现的最小滑动摩擦，因此非常重要。一般认为，当润滑剂层的厚度与表面粗糙度的幅度相当时，发生从EHL到ML状态的过渡。在这里，据报道，在光滑，柔软，聚（二甲基硅氧烷）基板上的润滑滑动实验中，当液体层的厚度远大于凹凸不平的高度时，可以发生过渡。“接触”区域的直接可视化显示，过渡对应于在前接触边缘处形成波状表面褶皱以及在后接触边缘处形成相关的不稳定性，这被认为触发了向混合状态的过渡。这些结果改变了对软固体润滑滑动中重要的EHL-ML转变的理解。
Lubricated contacts in soft materials are common in various engineering and natural settings, such as tires, haptic applications, contact lenses, and the fabrication of soft electronic devices. Two major regimes are elasto‐hydrodynamic lubrication (EHL), in which solid surfaces are fully separated by a fluid film, and mixed lubrication (ML), in which there is partial solid‐to‐solid contact. The transition between these regimes governs the minimum sliding friction achievable and is thus very important. Generally, the transition from EHL to ML regimes is believed to occur when the thickness of the lubricant layer is comparable with the amplitude of surface roughness. Here, it is reported that in lubricated sliding experiments on smooth, soft, poly(dimethylsiloxane) substrates, the transition can occur when the thickness of the liquid layer is much larger than the height of the asperities. Direct visualization of the “contact” region shows that the transition corresponds to the formation of wave‐like surface wrinkles at the leading contact edge and associated instabilities at the trailing contact edge, which are believed to trigger the transition to the mixed regime. These results change the understanding of what governs the important EHL–ML transition in the lubricated sliding of soft solids.