An ultra-low frictional interface combining FDTS SAMs with molybdenum disulfide

Abstract

Interfacial friction is of crucial importance to ensure the friction-reducing and anti-wear properties of mechanical microstructures in micro/nanoelectromechanical systems (MEMS/NEMS). An ultra-low frictional interface combining hydrophobic 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) self-assembled monolayers (SAMs) coated on an AFM tip with mechanically exfoliated molybdenum disulfide (MoS₂) nanosheets deposited on a planar Si/SiO₂ substrate was achieved. The FDTS SAMs/MoS₂ interface between the FDTS SAMs and the MoS₂ nanosheets exhibits an ultra-low friction force that is independent of the relative humidity. The incommensurate contact with ultra-low energy dissipation between FDTS and MoS₂ nanosheets and hydrophobic surface properties lead to this ultra-low frictional FDTS SAMs/MoS₂ interface. Also, the MoS₂ nanosheets have a high elastic modulus, which gives them a smaller contact area than the FDTS SAMs and contributes to the low friction. The excellent hydrophobic properties of both the FDTS SAMs and MoS₂ enable them to be unaffected by the relative humidity by preventing the capillary interaction. This study paves the way for extensive applications in reducing the friction of nanoscale contact interfaces.