ADHESION OF SOLIDS

We report results of studies of adhesion of two solids on a microscopi c level. We show that the Johnson-Kendall-Roberts theory [Proc, R. Soc . London A 324, 301. (1971)] remains valid even at this level, and tha t the effects of roughness and an intervening fluid can be accounted f or by adjusting the value of the work of adhesion. We study adhesion h ysteresis and demonstrate that, in our system, it arises from bulk eff ects. We also find that the detachment of spherical particles from sol id surfaces occurs at smaller values of the shear rate than predicted by continuum theory, due to slip between the particle and the solid su rface which is not taken into account by continuum theories.