Nanoscale friction could lead to surface improvement

In search of low-friction components for nanosystems, the physicists led by professors Thorsten Hugel and Alexander Holleitner examined how and why single polymer molecules in various solvents slide over or stick to certain surfaces.

Their goal was to understand the basic laws of physics at the molecular scale in order to develop targeted anti-friction surfaces and suitable lubricants.

For their studies the scientists attached the end of a polymer molecule to the nanometre-fine tip of an atomic force microscope (AFM). While they pulled the polymer molecule over test surfaces, the AFM measured the resulting forces, from which the researchers could directly deduce the behaviour of the polymer coil.

Besides the two expected friction mechanisms such as sticking and sliding the researchers detected a third one for certain combinations of polymer, solvent and surface. The researchers dubbed this ‘desorption stick’.

‘Although the polymer sticks to the surface, the polymer strand can be pulled from its coiled conformation into the surrounding solution without significant force to be exerted,’ said Prof Hugel. ‘The cause is probably a very low internal friction within the polymer coil.’