Manipulation of an Ag ND. The solid black arrow indicates the direction of the tip movement, and the dashed black arrow shows the direction of oscillation of the tip (a). The ND rolls over approximately 90° (a, b), then rotates around one of its bulbs (b-d) and finally runs into a NW (d). White arrows indicate the type of motion. Corresponding tip-dumbbell interaction force in time was recorded by a QTF sensor (e).