Aspect ratio and dimension effects on nanorod manipulation by atomic force microscope

This Letter deals with modelling of nanorod manipulation using an atomic force microscope (AFM). Widespread application of nanorods and a lack of real-time imaging in nanotechnology make process modeling necessary. This model considers three basic nano forces: van der Waals, friction and adhesive contact force for a quantitative analysis of effective parameters. A dynamic analysis of nanorod pushing considering depression on an elastic substrate, indention between tip-nanorod and deflection along a straight path is presented. Incorporating a beam on the elastic substrate assumption, a complete model for nanorod manipulation is introduced. The model is verified using available (theoretical and experimental) results. A polystyrene nanorod is simulated and critical force and time, maximum deflection and safety factor are obtained. Aspect ratio and dimension effects are the most significant contributions of this work. Also, it is determined that the dynamic modes of micro- and nanorods are different. Despite rolling being a dominant mode in microrod manipulation, sliding is observed in nanorod pushing as the dominant dynamic mode. Results show that an increase in length causes considerable deflection and decrease in the safety factor.