Effect of Bonded Molecules on Replenishment of Lubricant-Depleted Area Created by Sliding on Molecularly Thin Lubricant Film

The effect of a bonded lubricant on the replenishment of a lubricant-depleted area was examined. The replenishment process for a monolayer perfluoropolyether lubricant with different bonding ratios was imaged in real time using two-stage imaging ellipsometric microscopy. The relationship between the diffusion coefficient and bonding ratio was evaluated by comparing the experimental results with those of lubricant diffusion simulation. The diffusion coefficient of the replenishment process agreed with that of spreading on a disk with bonded lubricant, which suggests that the replenishment process can be modeled by the diffusion of mobile lubricant molecules through bonded ones.