Controlled manipulation of rigid nanorods by atomic force microscopy

Abstract

The motion of rigid nanorods caused by the normal vibrations of a nanotip rastering a flatsurface is described within an original collisional model. Provided that the frictionbetween the nanorods and the surface is sufficiently high, the direction of motionand the orientation of the nanorods are determined by two pairs of differentialequations. In the limiting case of thin nanowires, the direction of motion is preciselyrelated to the length of the nanowire, the tip radius and the density of the scanlines. At the same time the wire oscillates perpendicularly to this direction ina characteristic wobbling motion. Similar conclusions approximately hold alsowhen the rod thickness is not negligible (compared to its length), as shown by acomparison between numerical solutions of our model and measurements on goldnanorods manipulated on a silicon oxide surface. Our results open the path tounderstanding and controlling the manipulation of arbitrarily shaped nanoparticles.