Blow-Off Flow of Nano PFPE Liquid Film at Hard Disk Surfaces

Blow-off test was conducted for two different types of perfluoropolyether (PFPE): non-functional PFPE Z25 and functional PFPE Zdol3000. The film thickness of PFPE during the blow-off test was monitored intermittently in terms of ellipsometry. It is found that the two types of PFPE show completely different rheological behavior; micro-slip at the hard disk surface was observed for the non-functional PFPE Z25, while there was no micro-slip for the functional PFPE Zdol3000. Experimental results were analyzed theoretically, and it is found that micro-slip velocity of Z25 decreases steeply at first with the increases in the distance from the front end and then reaches a constant value, the film thickness in the front region increases with time due to the different micro-slip velocity, and a pileup layer is formed in the region. The pileup layer has a much lower viscosity than the original layer.