In-situ Observation of Lubrication Dynamics between Soft Elastomer and Glass Substrate

Direct observation is done for the thin lubrication layer in the friction between glass plate and soft elastomer using laser interference method. A poly(dimethylsiloxane) (PDMS) rubber having very flat surface was used as soft elastomer and water is used as lubricant. The surface of PDMS was modified by evaporation of a few dozen micron meters of Au layer in order to increase the reflectivity. It is observed that when the sliding velocity exceeded ca. 10 -3 m/s, lubricant intrude into the dry zone from the outer edge, and that the decrease of the friction is due to the decrease of the dry area. This phenomenon is interpreted by the theory of Brochard et al.