[tt] nested chiral CNT rotates in voltage gradient

[Eugen Leitl]

(Elegant, should this be validated)

http://technology.newscientist.com/channel/tech/dn14111-electron-turbine-could-print-designer-molecules.html?feedId=online-news_rss20

Electron turbine' could print designer molecules

    * 12:31 11 June 2008

    * NewScientist.com news service

    * Kate McAlpine

A simple microscopic motor can be made by slotting three nanotubes together
and hooking them to an electric current – the so-far theoretical design could
be used as a tiny printer to make designer molecules (Image: C Lambert)

A carbon nanotube that spins in a current of electrons, like a wind turbine
in a breeze, could become the world's smallest printer or shrink computer
memory, UK researchers say.

The design is simple. A carbon nanotube 10 nanometres long and 1 nm wide is
suspended between two others, its ends nested inside them to form a rotating
joint. When a direct current is passed along the tubes, the central one spins
around.

That design has as yet only been tested using advanced computer simulations
by Colin Lambert and colleagues at Lancaster University, Lancashire, UK.

But Adrian Bachtold of the Catalan Institute for Nanotechnology, who was not
involved in the work, intends to build the electron turbines and says it
should be straightforward.

Researchers have made or designed a range of small-scale motors in recent
years, using everything from DNA to light sensitive molecules to
cell-transport proteins.

The Lancaster design is one of the simplest yet. Imagined applications for
nanomotors range from shrinking optical communications components to new
forms of computer memory.  Tiny turbine

Conventional water or wind turbines spin by deflecting oncoming air or water
in one direction. This causes a reaction force to push them in the opposite
direction.

Similarly, when electrons move through the nanotube turbine, they tend to
bounce off its spiral arrangement of carbon rings in a particular direction.
This redirects the electrons into a spiral flow, and causes the tube to
rotate in the opposite direction.

The Lancaster team is confident this electron "wind" can overcome any
friction forces that would prevent the middle tube spinning. They also hope
to minimise friction at the joints by making the nanotubes as smooth as
possible.  Tiny inkjet

The Lancaster researchers say their motor could be used to pump atoms and
molecules through the spinning middle tube. Multiple pumps could precisely
control a chemical reaction, driving atoms in a pattern to engineer new
molecules. "It's like a nanoscale inkjet printer," says Lambert.

Atoms pumped through the motor could also be used to represent digital data,
with an array of motors shuttling atoms between the 1 and 0 ends of the
middle tube to store or process information. This method could store data in
a space about 10 times smaller than today's state-of-the-art commercial
systems, says Lambert.

"The work of Lambert's group is exciting," says Bachtold, "the proposed
motors should be rather straightforward to fabricate". But he points out that
only experiments will reveal whether this new nanomotor design lives up to
its promise.

A paper on the electron windmills will be published in Physical Review
Letters this month. A pre-review version is available on the arXiv pre-print
website.