Tribology: Weak Interfaces in Action

Material wear during sliding contact is often of equal or greater importance than the coefficient of friction, for successful device operation. The above video shows a tungsten probe tip scratching a gold surface, eventually ploughing out some gold through the application of sufficient pressure. Observing processes like this directly is important for a better understanding of the mechanisms of material deformation at small scales.

Merkle, A.P. and L.D. Marks, Friction in full view. Applied Physics Letters 90(6): p. 064101, 2007

Behavior at the nanoscale can differ dramatically from the expected macroscale behavior, as this video shows. After adhering some gold to the end of this tungsten tip, the tip is withdrawn, and the extremely rapid diffusion of gold results in liquid-like behavior.

Merkle, A. and L.D. Marks, Liquid-Like tribology of gold studied by in situ TEM. Wear 265: p. 1864-1869, 2008