The state of vanishing friction known as super-lubricity is highly desirable to reduce parasitic energy loss. However, without efficient means to turn on and off the super-lubricity, it would be difficult to realize its full potential in engineering applications. Here we report that the nanoscale super-lubricity between amorphous silica tip and graphite basal plane can be tuned by physisorbing various molecules from the environment. In particular, the super-low fiction can be further reduced by about 54% in -pentanol vapor, but increases by around 25 and 45 times in water and phenol vapor respectively. The vapor molecules influence the friction by adsorbing onto the silica surface and being entrained into the sliding interface. Based on the structures of adsorbed molecules, it could be deduced that adsorbates with high conformational entropy can suppress the interfacial commensuration and enhance the super-lubricity, while the ones that can facilitate commensurate interactions with the graphite surface increase friction. This finding provides the basic principle enabling on-demand control of friction into and out of the super-lubricious state of solid interface.

中文翻译：

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通过分子吸附调节超润滑性


被称为超润滑性的摩擦消失状态对于减少寄生能量损失是非常理想的。然而，如果没有有效的手段来开启和关闭超润滑性，就很难充分发挥其在工程应用中的潜力。在这里，我们报告说，无定形二氧化硅尖端和石墨基面之间的纳米级超润滑性可以通过物理吸附环境中的各种分子来调节。特别是，超低摩擦力在正戊醇蒸气中可进一步降低约54％，但在水和苯酚蒸气中分别增加约25倍和45倍。蒸气分子通过吸附到二氧化硅表面并被夹带到滑动界面来影响摩擦。根据吸附分子的结构，可以推断，高构象熵的吸附物可以抑制界面相称性，增强超润滑性，而促进与石墨表面相称相互作用的吸附物则增加摩擦力。这一发现提供了实现按需控制进入和离开固体界面超润滑状态的摩擦的基本原理。