Probing the wear characteristics of graphene on flexible polymer substrates using a heated atomic force microscopy tip

Graphene is a useful solid lubricant for flexible micro/nanoelectromechanical systems (MEMS/NEMS) because of its beneficial mechanical properties. However, understanding the tribological and wear characteristics of graphene on polymer substrates under high-temperature conditions is essential for predicting whether graphene will fail as a solid lubricant for flexible substrates in high-temperature environments. Herein, the friction and wear characteristics of monolayer graphene on flexible polydimethylsiloxane (PDMS) substrates are studied by atomic force microscopy using a heated tip. The friction of graphene before wear is more stable than that of PDMS, demonstrating that graphene can be used as a solid lubricant to stabilize the stick-slip motion of the tip on the flexible substrate at elevated temperatures. The friction of graphene shows an increasing trend with the heating temperature increasing due to an enlarged tip-graphene contact area. However, the friction of graphene considerably decreases with the tip sliding velocity increasing at a speed of less than 0.5 µm/s, resulting from a reduced tip-graphene contact area. The thermally-induced wear of graphene is caused by the coupling effect of the temperature and the sliding velocity. These results can provide an in-depth understanding of graphene as a solid lubricant for flexible polymer-based MEMS/NEMS devices in high-temperature environments.