Self-folding of single- and multiwall carbon nanotubes

Long carbon nanotubes (CNTs) have many important applications. However, long CNTs may self-fold and therefore compromise their applications. The authors have determined the critical length for self-folding as 4πEI∕γ, where EI and γ are the CNT bending stiffness and binding energy, respectively. This simple expression has been verified by atomistic simulations. For single-wall CNTs, the critical self-folding length ranges from a few hundred nanometers to about 2μm. For multiwall CNTs, the critical length increases rapidly with the number of walls and exceeds 10μm for a 14-wall CNT.