Resonance Shear Measurement for Studying Confined Liquids

Abstract

Liquids confined in molecular-scale spaces show remarkably different properties from those of the bulk state due to the spatial limitation and the interactions between the liquid molecules and solid surfaces. We have developed the resonance shear measurement (RSM) based on the surface forces apparatus (SFA) and applied it for evaluating the viscosity and lubricity of confined liquids. This method utilizes the resonance signal of the top mechanical unit that sensitively changes depending on the properties of the confined liquids, offering a method with high sensitivity and stability. This article reviews the principle of RSM and applications of the measurement for tribology by providing examples of water between silica surfaces and pheny ether lubricants between mica. The future use of the measurement is described.