In summary, we again emphasize the very rich physics encountered in the study of multi-walled carbon nanotubes. In this review we gave, at best, a snap-shot of the present status of this rapidly changing field. As an illustration of the enormous potential of the multi-walled carbon nanotubes in basic and applied science, we present the manipulation of MWNTs of the Zettl group at Berkeley [166] of which we have become aware during the writing of this chapter. Describing their breakthrough, best summarizes the rapid progress of this field. They managed to peel a MWNT and to sharpen its tip at 'will' by using Joule heating applied via an STM tip in a transmission electron microscope (Fig. 38). The outer, supporting shortened cylinders reinforce the stability of the nanotube. This gives the possibility to improve considerably the resolution of a scanning probe tip. By attaching the STM tip to the innermost nanotube when the outer layers were peeled off, they have created an extremely low-friction nanoscale linear bearing and a constant force nano-spring. We believe that in the future such manipulations of MWNTs will revolutionize nanoscale architectures and studies at the nanoscale.

Fig. 38. Sequence of transmission electron microscope (TEM) images of a MWNT, showing the sharpening of the MWNT tip by applying current pulses with an STM tip [166]


The authors acknowledge the contributions to the work presented here by all their past and present collaborators, especially J.-M.Bonard, J.-P. Salvetat, A. Kulik, K. Hernadi, S. Pekker, Walt A. de Heer, D. Ugarte, A. Bachtold, and M. Buitelaar. The work in Lausanne and Basel is supported by the Swiss National Science Foundation Program NFP36.

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