UC Berkeley

Abstract: This report investigates the kinetics of lubricant molecules in the HAMR air bearing to understand the initiation and growth of PFPE contamination on the head surface. The collisions with the air bearing induce three forces—drag, thermophoresis, and lift. Of these, we find that lift forces are negligible. Then, a sensitivity analysis of the remaining two forces reveals the conditions where they dominate. Further, a hybrid simulation strategy is utilized to track their movements. The results show that the contaminations (smear) highly depend on the interplay between the thermophoresis and drag forces. We then explain the mechanism of the formation of the various observed patterns. Finally, we offer some recommendations to exploit the air bearing to contain smear on the head.