AFM AND IR STUDIES OF MOLECULAR ASSEMBLIES ON SILICA NANOASPERITIES FOR FRICTION MODIFICATION

摘要

Controlling friction, adhesion and wear of surfaces is of key importance to the proper function of micro-electromechanical systems (MEMS) devices. As the surfaces of these devices often exhibit nanoasperities on the order of 10 - 20 nm in dimension, the interactions between these nanoscopic asperities during intentional or intermittent contact will dominate the tribological properties of the surfaces. We have developed a simple platform on which molecular assemblies may be investigated on surfaces with controlled nanoscopic roughness. [1] Here, self-assembled monolayers (SAMs) of organosilanes on surfaces of controlled roughness have been examined by FTIR [2] and AFM to explore how film assembly and disorder impact friction and wear at these interfaces as a function of molecular chain length (C_8 - C_(18)) and asperity curvature. Importantly, disordered layers assembled on asperities can intercalate solvent molecules and act a means to store recoverable lubricant molecules, allowing for interfaces to be designed that will yield a slow release of lubricant into a wearing interface, to enable self-healing surfaces that exhibit reduced friction and wear. Here we have found that the uptake of short-chain alcohols by organosilane SAMs on silica nanoasperities yields films with reduced friction and enhanced resistance to wear.