Theoretical analysis of evaporation and re-adsorption of PFPE molecules on hard disk surface

The collision density of the evaporated lubricant molecules in the air with the hard disk was analyzed based on the kinetic theory of gases. It is found that the collision density is quite high even for the ultralow vapor pressure of the lubricant perfluoropolyether used in hard disks. This suggests that the adsorption of the collided molecules may have significant contribution to the lubricant film replenishment. In addition, the adsorption of the lubricant molecules is also expected to reduce the potential barrier to the surface diffusion, and hence to promote the spreading process of lubricant film on hard disk surface. An adsorbing–spreading mechanism is proposed for the lubricant film replenishment in hard disks.