Frictional characteristics of exfoliated and epitaxial graphene
  To determine the friction coefficient of graphene, micro-scale scratch tests are conducted on exfoliated and epitaxial graphene at ambient conditions. The experimental results show that the monolayer, bilayer, and trilayer graphene all yield friction coefficients of approximately 0.03. The friction coefficient of pristine graphene is less than that of disordered graphene, which is treated by oxygen plasma. Ramping force scratch tests are performed on graphene with various numbers of layers to determine the normal load required for the probe to penetrate graphene. A very low friction coefficient and also its high pressure resistance make graphene a promising material for antiwear coatings. 
Young Jun Shin, Ryan Stromberg, Rick Nay, Han Huang, Andrew T. S. Wee,   Hyunsoo Yang, Charanjit S. Bhatia
cond-mat.mtrl-sci cond-mat.mes-hall