Abstract
Over the past twenty years, thin film lubrication (TFL) theory has been used to characterize the molecular behaviors in lubrication films thinner than 100 nm, effectively bridging the gap between elastohydrodynamic lubrication and boundary lubrication. Unfortunately, to date, the TFL molecular model proposed in 1996 has not been directly proven by experimental detection. Herein, a method based on surface-enhanced Raman spectroscopy was developed to show both the packing and orienting of liquid molecules in the TFL regime. By trapping liquid crystal molecules between a structured silver surface and a glass surface, molecular ordering states dominated by shear effect and surface effect were successfully distinguished. A nanosandwich structure consisting of an adsorbed layer, an ordered-molecule layer, and a fluid layer was demonstrated. Molecule imaging in TFL was achieved. Our results illustrate the molecular behaviors and lubrication mechanism in nanoconfined films and facilitate the lubrication design of nanoelectromechanical and microelectromechanical systems.
Highlights
Molecules confined in a nanogap present special properties different from those at the macroscale [1,2,3,4]
Owing to the ultrathin film interferometry, Spikes et al directly observed a sub-nanometer liquid film and believed that there is no boundary film for hexadecane and both mono- and multi-layered structures exist for stearic acid within a nanogap without any layered orientations [19,20,21,22]
Our new approach induced both the Ag nanorod surface and the shear-flow field to direct the alignment of the 6CB molecules
Summary
Molecules confined in a nanogap present special properties different from those at the macroscale [1,2,3,4]. Owing to the ultrathin film interferometry, Spikes et al directly observed a sub-nanometer liquid film and believed that there is no boundary film for hexadecane and both mono- and multi-layered structures exist for stearic acid within a nanogap without any layered orientations [19,20,21,22] This updated technique suggested a layer structure by testing the thickness of the liquid film. In 1996, the TFL molecular model was developed by Luo et al [23] It proposed that different layers, composed of a fluidic film, ordered film, and adsorbed film, will be formed, and the lubricant molecules are differently oriented in each layer owing to the surface influence and shearing force. This work extends the applicability of the TFL model and initiates research on lubrication at the molecular level
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
