Unique buckling responses of multi-walled carbon nanotubes incorporated as torsion springs

Buckling responses of multi-walled carbon nanotubes incorporated as torsion springs in electromechanical devices are predicted via classical molecular dynamics simulations. The observations reveal that the outermost walls of the nanotubes act as torsion springs and possess not only greatly enhanced first buckling strengths, but also stiffened post-buckling regimes characterized by a slight growth of helicoidal ridges and furrows. As a result, a second buckling point appears at a larger torque than the first one, with a positive torsional stiffness of about 55% relative to the value in the pre-buckling regime. Interestingly, these unique buckling responses are mainly caused by the presence of the third outermost wall acting as a hard core.