Microbubble Phenomenon in Contact Area Between Soft Tribological Interfaces in Sliding Contact

The microbubble phenomenon in contact area between soft tribological interfaces in sliding conditions has been directly observed with a custom-built soft tribology instrument. Experimental results show that the formation of microbubble is due to surface instability. The surface instability in soft films arises from a competition between the adhesion forces and the elastic forces. There are two different mechanisms by which the microbubble phenomenon in contact area between soft tribological interfaces in sliding contact. When a shear force is imposed, the microbubble between PU and glass slide is due to surface buckling instability. For the softer rubber, the buckling does not occur in the thin interface layer between PDMS and glass slide and the contact front forms the microbubble edges. Theoretical analyses have been used to discuss the microbubble formation.