Carbon nanotubes

Cylinders and ropes from 0.8 nm to 50 nm in diameter, to many microns in length. These are TEM images. The upper left is a multi-wall nanotube, and the lower left is a matte of single-wall tubes. The lower right shows how single-wall tubes tend to form bundles or ropes.

The stress test: One experiment repeatedly bent a nanotube through contortions to see if it would break. All these modifications were performed by the NanoManipulator, with the user guiding the AFM tip by moving the Phantom force-feedback pen. 

Small bends have periodic ripples, which are reversible. They move along tubes freely depending on the location of the bend. Large bends form a kink with a height larger than expected and form a weak spot that tends to kink again.

Side view of a bend, showing periodic ripples nearest, and kinks further away. A similar image appeared on the cover of Nature magazine; see the reference at the end of this page.

Sliding a tube across the surface:

When the motion is modeled for several manipulations of different tubes, it shows the expected pivot point from a stiff rod sliding on a surface with uniform friction.

This is a different story: an off-center push doesn't re-orient this tube:

Instead, it rolls, like a round pencil on a smooth desk. How do we know it rolls?

bulletNo in-plane rotation
bulletTip end changes periodically
bulletLateral force periodic with circumference of nanotube

This nanotube is stable for imaging only in particular orientations, 60 degrees apart, same as symmetry of graphite lattice.

Two tubes moved over the same patch of graphite - their orientations are maintained through the collision. Helicity of the tube determines its lock-in orientation with the graphite substrate.

This is the lateral force measurement for this modification:

NEMS devices: building a nanotube bridge:

A side view of the bridge:

More details can be found in these references:

"Rolling and sliding of carbon nanotubes", M. R. Falvo, R. M. Taylor II, A. Helser, V. Chi, F. P. Brooks Jr., S. Washburn, and R. Superfine, Nature 397, 236 - 238. (1999) (PDF)

"Nanomanipulation experiments exploring frictional and mechanical properties of carbon nanotubes", M. R. Falvo, G. Clary, A. Helser, S. Paulson, R. M. Taylor II, V. Chi, F. P. Brooks Jr, S. Washburn, R. Superfine Microscopy and Microanalysis, 4, 504-512. (1998) (PDF)

"Bending and buckling of carbon nanotubes under large strain," M. R. Falvo, G.J. Clary, R.M. Taylor II, V. Chi, F.P. Brooks Jr., S. Washburn and R. Superfine, Nature 389, 582-584. (1997) (PDF)

Paulson, S., M. R. Falvo, N. Snider, A. Helser, T. Hudson, A. Seeger, R. M. Taylor, R. Superfine, and S. Washburn.  "In situ resistance measurements of strained carbon nanotubes."  November 8, 1999, Applied Physics Letters, Volume 75, Number 19, pp. 2936 - 2938.

Images and scientific content are courtesy of the University of North Carolina at Chapel Hill.