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Posted: July 4, 2007

Sensitive giant probes atomic world

(Nanowerk News) The vault in which the behemoth is housed is buried deep under the streets that flank the Albert Hall in London.
Once the double doors - designed to eliminate contamination of all kind, not just noise - suck shut, the room takes on the air of a mausoleum. Even the technicians and scientists gathered at the base of Titan, as the microscope is known, talk in hushed, respectful tones. But their silence is not just for the benefit of their fellow academics, it is an operational requirement of the machine.
“If the sample drifts, it kills the experiment,” said Dr David McComb of Imperial College London, where the microscope is housed.
With a machine that is able to image individual atoms, even the vibrations caused by talking too loudly are enough to shunt a sample. When scientists are operating at such small scales, tiny shifts can appear huge.
“The drift rate has got to be better than one nanometre per minute,” he explained. “It’s about how much your finger nail grows in one minute,” said Dr James Perkins, one of the research scientists who use the sensitive giant to probe the atomic structure of the world.
Random scatter
Titan is a transmission electron microscope, the first of its kind in the UK and one of only a handful found in labs around the world. Its maker, FEI Company, says it is the most powerful commercially available scope on the market. When it is running at full power it will be used to probe everything from new materials for ultra fast computers to tissue samples that may shed light on diseases such as Alzheimer’s.
The £2.4m ($4.8m) scope is capable of imaging objects just 0.14 nanometres in diameter, useful for probing the atomic structure and chemistry of materials. It works by firing electrons through an incredibly thin sample, just microns (one millionth of a metre) thick, and observing the changes to the particles as they pass through and out the other side.
“What happens to the electrons tells us about how the atoms were arranged in the sample,” said Dr McComb.
In essence, the trajectories of the electrons can be mapped, like snooker balls scattering on a table. Knowing their trajectory as they exit allows scientists to build up a picture of the internal structure of the sample. In addition, measuring the energy lost by electrons gives scientists clues about the identity of the atoms in the sample and how they bond together.
“That is enormously powerful,” said Dr McComb.
Research boost
The machine has been bought by the London Centre for Nanotechnology (LCN) using money from the Engineering and Physical Sciences Research Council (EPSRC). It was installed in August 2006 and should soon be running at full power. Already there is a raft of projects that could use the super-scope. Medical researchers, for example, hope to use it to uncover the secrets of bone disease.
“Clearly, if we want to tackle diseases like osteoporosis, we need new drugs and clinical trials,” said Dr McComb. “But in order to develop those we also need to understand the process of osteoporosis. We need to understand how bone and tissue interact and why that process changes as we get older.”
Teams have proposed to use Titan to examine the microscopic and chemical changes on the surfaces of bones in both healthy and diseased tissue. Other teams want to understand the role of iron metabolism in the development of Alzheimer’s disease.
“We are not quite sure what the state of the iron is or how it interacts with the tissues in the brain,” said Dr McComb. “But if we can understand that then potentially we can feed that into research into something that can disrupt or modify that process.”
Researchers from LCN are also queuing up to test new materials for efficient fuel cells and catalysts, as well as examining the atomic structure of semiconductors to optimise or boost their performance in future computers. Eventually, the knowledge gained will also allow scientists to start building materials atom by atom.
“We’re ramping up, we’re starting to get results,” said Dr McComb. “I expect over the summer we’ll really start rocketing.”
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