Can stick-slip motion and structural superlubricity (SSL), two seemingly incompatible interfacial states, coexist? A team led by Professor Quanshui Zheng at Tsinghua Shenzhen International Graduate School has observed an unexpected phenomenon at a superlubric gold (Au)/graphite interface: below a critical driving velocity, stable and controllable periodic stick-slip occurs while the interface retains a near-zero coefficient of friction and zero wear. The finding shows that stick-slip does not necessarily entail high friction and wear. It deepens our understanding of the fundamental behavior of sliding interfaces and suggests new approaches to controlled actuation in micro- and nanoscale devices.
Stick-slip is one of the most common phenomena at sliding interfaces, spanning scales from geological processes such as earthquakes and biological tactile perception to discrete motion at the atomic scale. Its inherent periodicity offers opportunities for precise control and provides insight into interfacial physics. However, stick-slip is usually associated with high friction and wear, causing vibrational noise, increased energy consumption and surface degradation that limit practical applications. Interface science has therefore long sought to suppress stick-slip to achieve low power consumption and extended operating lifetimes, motivating research into superlubricity. Within this field, SSL enables direct sliding between solid surfaces without lubricants, with ultralow friction and zero wear.
Whether stable, controllable periodic stick-slip can occur at an SSL interface has remained an open question. Previous studies have offered clues. Atomic force microscopy (AFM) tip experiments show that periodic energy barriers coupled to a compliant probe acting as a spring can produce stick-slip. Yet the role of the vanishingly small energy corrugations at incommensurate SSL interfaces remains debated. Superlubric metal/two-dimensional (2D) material interfaces also commonly exhibit anomalous static friction peaks. A comprehensive physical picture has been difficult to establish because boundary lubrication layers, frictional ageing, chemical bonding, moiré superlattices and edge effects complicate their interpretation.
Figure 1. Overview of the experimental system, results and proposed mechanism.
To address this question, the team fabricated, in situ under ultrahigh vacuum, interfaces between microscale single-crystalline Au mesas and single-crystalline graphite. Below a critical driving velocity, the interfaces exhibited stable periodic stick-slip while retaining key SSL characteristics: a near-zero differential coefficient of friction, stable friction over 3,000 sliding cycles, and wear-free sliding supported by the absence of a detectable defect-related D peak in Raman spectra of the graphite surface after sliding.
Friction showed a nonmonotonic dependence on velocity, with three regimes: nearly constant friction at low velocity, decreasing friction at intermediate velocity, and a sublinear increase at high velocity. The intermediate regime runs counter to the conventional expectation that friction increases with velocity. In control experiments, deliberately introducing water molecules and organic airborne contaminants into the interface eliminated the stick-slip behavior and changed its velocity dependence, supporting the conclusion that the observed behavior originates from the pristine Au/graphite interface.
The team proposed a weak-pinning mechanism in which sparse point vacancy defects on graphite capture isolated Au atoms that form metallic bonds with the underside of the Au mesa. In this picture, competition between thermally activated bond formation and force-induced bond rupture governs switching between static and dynamic friction. The resulting model predicts a scaling law for the critical velocity, which was verified by control experiments varying the mesa's twist angle and the probe stiffness. The observed increase in critical velocity with temperature is also consistent with thermally activated bond formation.
The study, titled “Observation of stick-slip behavior with structural superlubric characteristics,” was published in Nature Communications.
The first author is Weipeng Chen, who joined the doctoral program in mechanics at Tsinghua University's School of Aerospace Engineering in 2022. The corresponding authors are Quanshui Zheng, a member of the Chinese Academy of Sciences and a professor at Tsinghua Shenzhen International Graduate School; Deli Peng, an assistant professor at the same school; and Zhanghui Wu, an associate professor at the College of Mechatronics and Control Engineering, Shenzhen University. Other authors include Tielin Wu and Yelingyi Wang, postdoctoral researchers at Tsinghua Shenzhen International Graduate School; Wanying Zhao, who joined the school's doctoral program in mechanical engineering in 2025; and Jin Wang, a postdoctoral researcher at the International School for Advanced Studies (SISSA), Italy.
The research was supported by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, the European Research Council, and relevant science and technology programs in Guangdong Province and Shenzhen.
Article link: https://www.nature.com/articles/s41467-026-77734-3
Text and figure by Weipeng Chen