human computer interaction
natural computing
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Tobias Hertel, Robert Walkup, Richard Martel and Phaedon Avouris at IBM's Thomas J. Watson Research Center found that van der Waals forces -- attractive forces among atoms and molecules -- hold Nanotubes firmly against the surfaces they are placed on. Thus the researchers were able to change the Nanotubes' positions and orientations, and to alter their shape, by bending them. They distorted the Nanotubes in various ways using calibrated AFM forces; the strong interaction with the surface then stabilized the distorted Nanotubes. By applying particularly large forces, the researchers were able to cut the Nanotubes. For that to happen, however, the Nanotubes had to be anchored to the surface more firmly than normal, by means of chemical bonds rather than the physical van der Waals forces.

These studies led to the important conclusion that the van der Waals interaction between the Nanotubes and the surfaces on which they rest is itself strong enough to change the shape of Nanotubes. In general, they tend to adapt to the shape of the surface on which they sit by bending and becoming slightly squashed. Those changes can cause the properties of Nanotubes on surfaces to differ from those of perfect Nanotubes, which are straight and have circular cross-sections. This raises the possibility of tailoring Nanotubes' properties by intentionally changing their shapes.

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