Confinement-induced refractive index change
Equipment
Materials
Plain strain moduli for the experimental interfaces
Surface cleaning
Roughness measurement
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
To derive the gap between the surfaces through the intensity, the confocal microscope was turned into reflection mode. Reflection of the laser from the bead surface forms an interference pattern known as Newton rings. The maximal intensity of the reflection will occur when the distance between the surfaces isd=(m+12)λ2n(2)where m = 0, 1, 2, 3, … is the ring number, λ = 514 nm is the excitation wavelength, and n = 1.484 is the refractive index of the fluorescent liquid. Thus, correlation between intensity and thickness is obtained by taking and comparing a cross section of the fluorescence intensity image and that of the laser reflection image. For details, see (19).