Manipulating Matter into Tiny Machines


Nanomachines Get Their Orders
by Damian Carrington

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.

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