2015 Volume 15 Issue 5 Pages 205-211
In order to elucidate lubrication by liquids confined between solid surfaces, the resonance shear measurement (RSM), which we developed, is a powerful tool. RSM can evaluate the properties of confined liquids as a function of surface separation from μm to contact with nm resolution. Thus, it is especially useful for studying boundary lubrication where the lubrication layer becomes thin and solid surfaces are partially in contact. In this article, we describe the principle and advantages of RSM, and reviews our recent studies on nanoconfined liquids by using RSM: (i) four phenyl ether lubricants with different bulk viscosity exhibited significant increase in the viscosity when confined between mica surfaces (gap < ca. 20 nm), and the one with the lowest bulk viscosity showed the highest viscosity in a gap below 2–3 nm, (ii) water confined between silica surfaces exhibited better lubricity and load bearing property when the surface silanol density was increased, (iii) two ionic liquids confined between silica surfaces showed significant increase in viscosity and the their magnitude relation became reverse when they are confined in nano-space.
