( There's a limit to how tiny gadgets de...)Nanotechnologists Specify Limitation For Devising Small Machines ,Health

There's a limit to how tiny gadgets, devices and machines can get, scientists have claimed.

The claim comes from an experiment performed by a University of Arizona// team of optical sciences doctoral candidate John D. Perreault and assistant professor of physics Alexander D. Cronin.

Perreault and Cronin directly measured how close speeding atoms can come to a surface before the atoms' wavelengths change, said a statement from the university.

Theirs is a first, fundamental measurement that confirms the idea that the wave of a fast-moving atom shortens and lengthens depending on its distance from a surface, an idea first proposed by pioneering quantum physicists in the late 1920s.

The measurement tells nanotechnologists how small they can make extremely tiny devices before a microscopic force between atoms and surfaces, called van der Waals interaction, becomes a concern.

The result is important both for nanotechnology, where the goal is to make devices as small as a few tens of billionths of a metre, and for atom optics, where the goal is to use the wave nature of atoms to make more precise sensors and study quantum mechanics.

Perreault and Cronin reported the experiment in the latest issue of Physical Review Letters.

"Our research provides the first direct experimental evidence that a surface 25 nanometres away (25 billionths of a metre) causes a shift in the atom wave crests," Perreault said.

"It shows that the van der Waals interaction may be a small scale force, but it's a big deal for atoms."

Cronin said: "We might say that when an atom is between 10 and 20 nanometres from a surface, it gets sucked toward the surface with a force a million times its weight.

"And when it gets closer, it gets pulled even harder."

Perreault said: "I think the impact of our work stems from the intersection of the fields of atom optics and nanotechnology. It answer
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