Ubiquitous friction：from the macroscopic to the single-atom regime

Friction is a crucial and ubiquitous scientific issue in the history of human civilization and daily life, without which humans cannot live or create products；therefore, friction must be considered in all types of fabrication on the atomic scale. From macro to micro, friction is very complex, mysterious and intriguing! In the macroscopic regime, the classic da Vinci—Amontons law was established 500 years ago. However, in the microscopic regime, friction exhibits behavior that is quite distinct from those on the macroscopic scale, such as super-lubrication in which the friction coefficient is reduced to almost zero, and also negative friction in which the friction force decreases as the load increases. This presents a new perspective on controlling friction at the microscopic level. The present article briefly describes tribology and the history of its development, with a focus on micro-physical mechanisms and regulation of the origin of friction on the single-atom scale.