Nanomachines Get Their Orders
Source: BBC
News
April 13, 2000
Tiny gold balls gather into larger spheres which form networks
(image 350nm wide)
Nanotechnologists have taken two vital steps toward manipulating
matter into tiny machines
The first uses a polymer "glue" to persuade hundreds of thousands
of tiny nanoparticles to group themselves together into large, highly-ordered
structures.
The ordering is crucial. For example, each of the tiny particles
could be a memory element in a molecular computer. Without a very regular
arrangement, the computer would not be able to find the elements and store its
data.
The second advance allows single atoms to be pushed around and
positioned at room temperature. One futuristic possible use for this technology
could be editing DNA.
Orderly fashion
Creating spontaneous order in hundreds of thousands of gold balls
just two millionths of a millimetre across (nanometres) is no easy task. But Dr
Vincent Rotello at the University of Massachusetts and his colleagues have
achieved just that.
They used a polymer which acted like mortar, building the gold
"bricks" into a regular network.
"That's the key - multiscale ordering," Dr Rotello told BBC News
Online. "The particles are ordered from visible range all the way down to
molecular level.
"There's a whole bunch of people out there who have made molecular
devices, all floating around in solution.
"They are wonderful things but its much the same as taking a
computer hard drive, smashing it with a hammer, tossing it in the air and saying
'Look, we have a bunch of memory storage units'.
"If you can't order it, you can't address it, and if you can't
address it, you can't use it."
Dr Rotello said the next challenge is to "control the network
formation. The kinds of systems we are in the process of creating are ordered on
the scale of nanometres but are 10 to 20 micrometres across."
Atomic billiards
Control on the atomic level is the aim of Professor John Pethica
and colleagues at the University of Oxford, UK.
The bromine atom arrowed was moved after the lower image was
taken.
They have managed, at room temperature, to shunt single atoms of
bromine around a highly-polished copper surface, rather like a game of atomic
pool. Previously, this has only been possible for large molecules such as
buckminsterfullerenes.
Their "cue" was a scanning tunnelling electron microscope and
learning how to control it was one of the key breakthroughs. It turns out that
changing the current of the beam was the most reliable way in which to push the
atoms. Raising the current heats the atom and makes it skip away.
At room temperature, thermal energy means the beam can easily
slide out of position. The team compensated for this by shaking the beam a
little, so it was sure to hit the target atom.
Data storage
BBC News Online asked Professor Pethica what future uses he saw
for the new-found nano skills: "That's a tricky question! It is important for
understanding basic physical processes in atomic-sized structures and future
quantum devices.
"And ultra-high density data storage has been also been
considered, though there are difficulties.
"In the longer term, it would be interesting to be able to
manipulate and alter organic molecules - some people dream of 'editing' DNA, but
I think that is rather far off."
Both teams' research was published in the journal Nature.
by
Damian Carrington
http://news.bbc.co.uk/hi/english/sci/tech/newsid_712000/712191.stm