Nanotube manipulation

 

 

In order to make devices out of nanotubes, it is important to be able to manipulate the nanotubes in a controlled way. We have developed the capability of changing a nanotube's position, shape and orientation, as well as cutting it. To accomplish this, we use an atomic force microscope (AFM).

 

 

The AFM is first used in "non-contact" mode to obtain an image of the nanotube by scanning the AFM tip, shown in red in the schematic on the left, just above the surface.

 

The AFM tip is then brought down to the surface and is used like a tiny plow to move the nanotube.

 

Because of the strong interaction between the nanotube and the surface via van der Waals forces, the bent Nanotube stays where it has been placed and maintains its shape, rather than snapping back to its preferred straight configuration.

 

 

Below is a series of AFM images illustrating the stepwise positioning of a nanotube across an insulating barrier so as to be able to pass current through it.

 

 

A single nanotube (in red) originally on an insulating substrate (SiO₂, shown in green) is manipulated in a number of steps onto a tungsten film thin wire (in blue), and finally is streched across an insulating tungsten oxide barrier (in yellow).

 

 

 

 

On the left we show another example of how a nanotube can be manipulated to form complex shapes: the 6 frames are a series of AFM images of a nanotube (orange) on a silicon substrate (blue). Not all steps are shown. The AFM tip is used to create the Greek letter "theta" from a 2.5 micron long nanotube.