Very low friction for diamond sliding on diamond in water

This letter reports the lowest coefficient of friction measured for diamond sliding on diamond. When a natural diamond stylus with a spherical tip about 50 μm in diameter slides on a polished polycrystalline chemically vapor deposited diamond film in water at a speed of 0.05 mm/s under a load of 50 g, the coefficient of friction falls to ∼0.001. This clearly shows the effectiveness of water for lubricating diamond sliding on diamond.