Microscopy
Confinement-induced refractive index change
Equipment
Materials
Plain strain moduli for the experimental interfaces
Surface cleaning
Friction
Contact area and load-bearing area size and average thickness of liquid layer calculation
Slope, root-mean-square roughness of the surfaces, and pressure
Average thickness measurement during sliding
Connection between theory and experiment
Viscosity as a function of specific film thickness
Predicted friction coefficient
Plasticity in glass-on-glass contacts
Calculation of the average contact pressure
Fluorescent liquid adsorption
Change of dry friction coefficient with roughness and waiting time
Roughness measurements were done using a 3D laser scanning microscope (KEYENCE VK-X-1000). Surface roughness Sq was measured after the sliding experiments and calculated as the root-mean-square height variation over an area of 150 μm by 100 μm measured at a resolution of 108 nm per pixel. Because Sq can depend sensitively on the cutoff length and sampling rate, we vary the resolution and size of the measurement area (fig. S10).