Investigating the motion modes of smooth/rough micro/nanoparticles with circular crowned roller geometry and computing the maximum force

The exact positioning of micro/nanoparticles is essential in the construction of micro/nanoscale structures. Of course, the shape of a particle and the external force application location on it influence the type of behavior exhibited by that particle during its displacement on a surface. In former works, biological and non-biological particles have been modeled as cylindrical or spherical particles, while the shape of many such particles is a combination of these two geometries. In this paper, the driving and displacement of particles with circular crowned roller geometry on a substrate by means of an AFM cantilever tip have been modeled three-dimensionally. For a more realistic modeling of actual particle conditions, the Cooper model has been developed for this geometry and the effects of surface roughness have been incorporated into the model. By using the presented model, the forces applied on particle during the manipulation process, the deformations induced in the AFM cantilever, the rotation center and the maximum force applied on particle can be computed and the motion modes of particle (sliding, rolling, rotating) at the onset of displacement can be predicted. The findings indicate that the critical forces associated with rough particles are smaller than those for smooth particles. Furthermore, the effects of particle dimensions and roughness parameters such as the radius and height of asperities and also the effect of AFM tip location on a particle on its motion modes have been studied and the suitable conditions for creating different motion modes have been discussed.