New states of matter via designer atoms

April 4, 2002 at 2:20 PM
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EDINBURGH, Scotland, April 4 (UPI) -- Scientists have found new states of matter by working with microscopic beads as if they were designer atoms, two research teams reported Thursday.

The novel glasses and crystals the investigators discovered using suspensions of spheres known as colloids may result in everything from microchips based on light instead of electricity to a better understanding of ketchup.

"This is all quite a big surprise," said researcher Wilson Poon, a physicist at the University of Edinburgh in Scotland. "There may be potential implications in biology -- similar things could happen in living systems."

Scientists led by physicist Krassimir Velikov at Utrecht University in the Netherlands discovered a completely new kind of crystal structure using silica beads only microns wide, each thinner than a human hair.

Unlike crystals made with atoms or molecules, crystals made of colloids can program their building blocks with desired properties to act like "designer atoms," according to Daan Frenkel of the Institute for Atomic and Molecular Physics in Amsterdam.

This new crystal structure has never been observed in molecular systems and could never have formed spontaneously.

"Such colloids can be used to confine, switch and amplify light," Frenkel said.

Velikov told United Press International these kind of "photonic crystals" may help lead to new light-speed fast microchips and optical fibers.

Poon's group and colleagues in Spain and Sweden discovered new states of matter while working with a glassy colloid made of plastic beads suspended in organic liquid. Glassy materials such as amber are more akin to highly viscous, immobilized fluids than solids.

Oddly enough, by making the plastic beads stickier by adding polystyrene -- the material that makes up Styrofoam -- they discovered their substance then flowed. This is like finding out glue can loosen up a bed of packed balls.

"It's absolutely counterintuitive -- they've shown you can kind of melt that glass simply by adding a small amount of attraction," said ceramics specialist Jennifer Lewis at the University of Illinois at Urbana-Champaign. "The results they've reported here are really exciting."

The researchers found there actually are two different states of glass. A glass apparently forms either because its ingredients are attracted together or because they are crowded together so tightly they cannot move, even though they repel each other. By making the ingredients more attractive, they transformed a material from one glassy state to another, each of which has a different flow rate.

"This could be extremely important in ceramics," Poon told UPI. Ceramics are made with grainy pastes. This discovery could help control how sticky the pastes are before they are fired in kilns, "allowing us to design ceramics in a controlled way -- for example making them stronger, or any other designed property," he explained.

Food science and biology are rich with colloids, examples including ketchup and blood. Lewis said this newly discovered shift in glassy behavior might be found in either fluid.

"In particular, it would be interesting to know whether nature employs similar tricks to control the mechanical properties of gels in living organisms," Frenkel said.

The two research teams described their findings in the journal Science.

(Reported by Charles Choi in New York.)

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