Observation of normal-force-independent superlubricity in mesoscopic   graphite contacts
  We investigate the dependence of friction forces on normal load in incommensurate micrometer size contacts between atomically smooth single-crystal graphite surfaces under ambient conditions. Our experimental results show that these contacts exhibit superlubricity (super-low friction), which is robust against the application of normal load. The measured friction coefficients are essentially zero and independent of the external normal load up to a pressure of 1.67 MPa. The observation of load-independent superlubricity in micro-scale contacts is a promising result for numerous practical applications. 
Cuong Cao Vu, Shoumo Zhang, Michael Urbakh, Qunyang Li, Q.-C. He, and   Quanshui Zheng
cond-mat.mes-hall