Magazine article Science News

An Appetite for Liquid-Crystal Spaghetti

Magazine article Science News

An Appetite for Liquid-Crystal Spaghetti

Article excerpt

An appetite for liquid-crystal spaghetti

Ordinarily, when a liquid cools it becomes a solid. Some substances, however, go through an intermediate, liquid-crystal phase, settling into an arrangement lying somewhere between the regular order found in crystallinge solids and the disorder in liquids. A new material shows how dramatic and unusual the change of state from a liquid to a liquid crystal can be.

Slowly cooling the pure-liquid form of this particular material initially produces tiny filaments visible under an optical microscope. Each filament grows longer and longer by adding material not to its ends by everywhere along its length. As the pace of growth accelerates, the filaments lengthen rapidly and fold into convoluted patterns. Within a minute, the entire field of view fills with a spaghetti-like tangle.

Then another curious thing happens. Suddenly, one or more small, compact lumps resembling flattened meatballs appear among the strands. The lumps quickly suck up the strands, clearing space for new filaments to form and grow. More and more lumps develop until the whole material finally ends up in a single, conventional liquid-crystal phase.

"When I first saw it, I found it quite unbelievable," says Peter Palffy-Muhoray of Kent (Ohio) State University. "I think it's the most complicated phase change in a pure material that I have ever heard of. It looks like a biological system." Palffy-Muhoray described the discovery in St. Louis this week at a meeting of the American Physical Society.

He and his collaborators are studying the new material as part of a general effort to gain a better understanding of how phase changes occur and how patterns form from liquids that themselves appear to have no structure. …

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