Cavitational Film-Splitting of Lubricants

We report work in which an oil film is stretched between a moving colloid sphere and a static plane surface. Under some circumstances, when the sphere and the surface are pulled apart sufficiently rapidly, an unexpected transient decrease of the sphere-surface separation is recorded. Numerical simulations indicate that cavitation bubble growth may result in the development of sufficient tension to account for this phenomenon: a finding confirmed by separate acoustic experiments and high speed microphotographic work.