Nanotube (carbon nanotube) A carbon nanotube (CNT) is a miniature cylindrical carbon structure that has hexagonal graphite molecules attached at the edges. Nanotubes look like a powder or black soot, but they're actually rolled-up sheets of graphene that form hollow strands with walls that are only one atom thick. Nanotubes, which are sometimes called buckytubes, were developed from the Fullerene, a structure that is similar to the geodesic domes. Nanotubes, which are grown in a laboratory, are strong and exhibit many thermal and electrical properties that are desirable to chip makers. Carbon nanotubes have the potential to be used as semiconductors, for example, potentially replacing silicon in a wide variety of computing devices. Nanotubes can be characterized by their number of concentric cylinders, cylinder radius and cylinder length. Some nanotubes have a property called chirality, an expression of longitudinal twisting. Multiple nanotubes can be assembled into microscopic mechanical systems called nanomachines. See also: Nanotechnology