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Engineering of Nanotube Geometry



  • Catalysts
  • Biological cell electrodes
  • Nanoscale electronics
  • Scanned probe microscope and electron field emission tips
  • Biological sensors
  • Manipulation probes


  • Systematically engineers nanotubes with made-to-order wall diameters and tip geometries
  • Can produce single-walled nanotube tips

Transmission electron microscope images of a multiwall carbon nanotube being shaped. (a) A nanotube in its pristine form: it contains approximately 37 walls and has an outer radius of 12.6 nm. (b) A carbon onion has been inadvertently transferred to the nanotube end from the shaping electrode, but no attempt has been made to shape the nanotube. (c)(d) Results of the subsequent peeling and sharpening processes: the onion has simultaneously been displaced to a benign position down the tube axis. The shaped, or 'engineered', nanotube in (d) is thick and mechanically rigid along most of its length (not seen in the image), but tapers stepwise to a fine sharp tip that is electrically conducting and ideal for scanning probe microscopy or electron field emission applications. The final long nanotube segment contains three walls and has an outer radius of 2.1 nm.  


Alex Zettl and John Cumings have developed a novel, reliable technique to systematically engineer the walls and tips of multiwall carbon nanotubes. The method works by the controlled peeling of individual outer carbon layers of the nanotubes, thus producing nanotubes with made-to-order diameter and tip geometries. This method allows highly controlled shaping through electrically driven vaporization of successive layers (i.e., tube walls) of the multiwall nanotubes. Later, outer nanotube layers are successively removed, leaving the core nanotube walls intact and protruding from the bulk of the multiwall nanotube.

This peeling and sharpening process can be repeatedly applied to the same multiwall nanotube until the very innermost, small diameter tube or tubes protrude — often with a tip radius of curvature comparable to that of a single-walled nanotube. Berkeley Lab's new method has been demonstrated in a transmission electron microscope (TEM) configured with a custom-built, mechanical/piezo manipulation stage with electrical feedthroughs to the sample. However, the method can be performed without the aid of a TEM as well.

Carbon nanotubes, due to their unique mechanical and electrical properties, are attractive candidates for a host of applications, including: catalysts; biological cell electrodes; nanoscale electronics; and scanned probe microscope and electron field emission tips. For many such applications, it is desirable to control or shape nanotube geometry. For example, the ideal scanned probe, field emission, or biological electrode tip would be long, stiff, and tapered for optimal mechanical response, and have an electrically conducting tip. Until now, this finely controlled nanotube shaping has not been possible. The ability to selectively shape the geometry on individual multiwall nanotubes has numerous applications in imaging (such as atomic force and scanning tunneling microscopy), field emission tips, and biological sensor and manipulation probes.


STATUS: U.S. Patent #6,709,566. Available for licensing




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