Very low viscosity at the solid-liquid interface induced by adsorbed C-60 monolayers

MOLECULES of C-60 (refs 1-4) are near-perfect spheres, and in the crystalline solid each molecule rotates rapidly while remaining at its lattice position. Speculation that this property may be conducive to good lubrication has not been borne out by experiments, at least for C-60 on its own(5-8). Here we report measurements of the intermolecular interactions of C-60 adsorbed as monolayers on surfaces immersed in a liquid. We find that the adsorbed layers impart a surprising effect on the flow properties of the liquid at the surface. The measured short-range oscillatory force indicates weak adsorption of one to two layers of C-60 on each surface. In the presence of adsorbed layers, fluid flow between two surfaces exhibits full-slip (zero drag) boundary conditions, giving rise to flow behaviour that is totally different from conventional fluid flow through narrow pores. This suggests that C-60 might be effectively used as an additive to conventional lubricant fluids.