Friction measurement and motion state determination of a single polystyrene nanoparticle during manipulation

Over the past two decades, the manipulation of nanoparticles has attracted increasing attention. This process provides essential information about tribology, which is of great significance for the exploration of the origin of friction. However, the motion state of the nanoparticles during this process must first be determined. Furthermore, since the nanoparticles could slide, roll, or spin when manipulated by the probe of the atomic force microscope, it was difficult to distinguish whether the force measured in the experiments denoted sliding or rolling friction. In this Letter, considerable manipulation and friction measurement experiments were performed, while the theoretical rolling and sliding friction were calculated using the Double-Hertz model. Furthermore, by comparing the theoretical calculations and experimental results, the motion state of the nanoparticle could be determined. Additionally, it was found that the critical rolling distance, which is essential for calculating rolling friction, decreases as the particle size increases.