The van der Waals cohesive force between two carbon nanotubes

The van der Waals cohesive forces acting at a single contact between two carbon nanotubes were experimentally investigated. An isolated nanotube was brought in contact with another one under observation by transmission electron microscopy. The cohesive forces of contacted nanotubes were obtained as the separation forces of the contact, which were estimated from the deflection and Young's modulus of nanotubes. As a result, the cohesive forces at cross-contacts ranged from 1.7 to 8.5 nN and increased with the increase in the diameter of nanotubes. The closed cap of the nanotube indicated a nine times larger cohesive force than that of the sidewall.