FRICTION AND WEAR OF LANGMUIR-BLODGETT-FILMS OBSERVED BY FRICTION FORCE MICROSCOPY

Lubrication is documented on a microscopic scale with a friction force microscope. A reduction in friction is observed for Langmuir-Blodgett film-covered surfaces, compared to the bare substrates. Film defects not detected in the topographic mode are clearly recorded in the friction force mode. With applied forces over 10 nN, the initial stages of wear are observed. Small islands of bilayer height are moved in their entirety, conserving the normal orientation of the aliphatic chains. This collective motion of molecules allows the shear strength of the films to be determined. The observed ability of the molecules to remain in the ordered state illustrates one of the fundamental origins of boundary lubrication.