Single-molecule manipulation experiments to explore friction and adhesion

Friction forces, which arise when two bodies that are in contact are moved with respect to one another, are ubiquitous phenomena. Although various measurement tools have been developed to study these phenomena at all length scales, such investigations are highly challenging when tackling the scale of single molecules in motion on a surface. This work reviews the recent advances in single-molecule manipulation experiments performed at low temperature with the aim of understanding the fundamental frictional response of single molecules. Following the advent of ` nanotribology` in the field based on the atomic force microscopy technique, we will show the technical requirements to direct those studies at the single-molecule level. We will also discuss the experimental prerequisites needed to obtain and interpret the phenomena, such as the implementation of single-molecule manipulation techniques, the processing of the experimental data or their comparison with appropriate numerical models. Finally, we will report examples of the controlled vertical and lateral manipulation of long polymeric chains, graphene nanoribbons or single porphyrin molecules that systematically reveal friction-like characteristics while sliding over atomically clean surfaces.