Wear-free sliding electrical contacts with ultralow electrical resistivity.

Sliding electrical contacts are commonly applied in electrical connectors, such as conductive slip rings, pantographs, switches, and commutators. However, they suffer from several unavoidable problems caused by friction and wear, including high energy consumption, intermittent failures, limited life, and even failure disasters. In this study, we realized an ultralow-friction and long-distance wear-free state, defined as structural superlubricity (SSL), between sliding electrical interfaces under ambient conditions. A conductive SSL can be implemented in experiments with single-crystal graphite flakes on flattened metals, such as Au and Ni films. Furthermore, we found that depositing a 2 to 3-nm-thick diamond-like carbon (DLC) film on a nickel alloy can lead to an even lower resistivity than that of metals alone. In addition, we revealed the mechanism by which DLC films can improve the conductivity between graphite and metals through density functional-theory simulations. In addition, we prepared a prototype of the SSL slip ring and proved that it possessed ultralow friction, was wear-free, and had no intermittent failures. Consequently, our results demonstrate a unique type of electrical-contact interface for applications requiring conduction while sliding. Thus, we opened the door for SSL electromechanical coupling.