title: Observation of microscale superlubricity in graphite.
abstract: Upon shearing a microscale lithographically defined graphite mesa, the sheared section retracts spontaneously to minimize interface energy. Here, we demonstrate a sixfold symmetry of the self-retraction and provide a first experimental estimate of the frictional force involved, as direct evidence that the self-retraction is due to superlubricity, where ultralow friction occurs between incommensurate surfaces. The effect is remarkable because it occurs reproducibly under ambient conditions and over a contact area of up to 10×10  μm2, more than 7 orders of magnitude larger than previous scanning-probe-based studies of superlubricity in graphite. By analyzing the sheared interface, we show how the grain structure of highly oriented pyrolitic graphite determines the probability of self-retraction. Our results demonstrate that such self-retraction provides a novel probe of superlubricity, and the robustness of the phenomenon opens the way for practical applications of superlubricity in micromechanical systems.
authors.affiliation: Department of Engineering Mechanics and Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China. zhe.liu@monash.edu
authors.forename: Ze
authors.initials: Z
authors.lastname: Liu
authors.forename: Jiarui
authors.initials: J
authors.lastname: Yang
authors.forename: Francois
authors.initials: F
authors.lastname: Grey
authors.forename: Jefferson Zhe
authors.initials: JZ
authors.lastname: Liu
authors.forename: Yilun
authors.initials: Y
authors.lastname: Liu
authors.forename: Yibing
authors.initials: Y
authors.lastname: Wang
authors.forename: Yanlian
authors.initials: Y
authors.lastname: Yang
authors.forename: Yao
authors.initials: Y
authors.lastname: Cheng
authors.forename: Quanshui
authors.initials: Q
authors.lastname: Zheng