PhD Student, part-time RA
To elucidate the relationship(s) between friction forces and charges, experiments at well-defined interfaces are required. A crucial simplification is achieved by reducing one of the surfaces in contact with the other down to a single asperity. Such single-asperity contact experiments are performed using an atomic force microscope (AFM), which is a tool that can detect forces down to atomic the scale. In this approach, the (normal) interaction between a sharp probe (“tip”, the asperity used in friction experiments), is regulated while other physical quantities involved (e.g. lateral force, potential) are varied/monitored. The figure shows an example of friction control by charges deposited/injected previously by the biased AFM tip.