Mother-of-pearl on ice.Pearls are some of the more beautiful examples of nature's strength. The gemstones grow inside oysters, and they are remarkably sturdy and tough. Now, scientists have found a way to copy what oysters have been doing all along. They've made a pearl-like material that could some day be useful for replacing weak bones and making machines. What's more, the method promises to be easy, cheap, and kind to the environment. Oysters, abalone abalone (ăbəlō`nē), popular name in the United States for a univalve gastropod mollusk of the genus Haliotis, members of which are also called ear shells, or sea ears, as their shape resembles the human ear. , and some other mollusks have a strong layer of armor called nacre nacre: see mother-of-pearl. (or mother-of-pearl). The substance is made out of tiny crystals and proteins, pieced together like the bricks and mortar A store (shop, supermarket, department store, etc.) in the real world. Contrast with clicks and mortar. of a brick wall. Their structure makes these natural materials sturdier than any human-made ceramics (a category that includes clay, cement, and glass). Scientists have long tried to mimic the architecture of these creatures' shells, with little success. Researchers at the Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory and Lawrence Livermore National Laboratory, scientific research centers run by the Univ. of California, located in Berkeley, Calif., and Livermore, Calif., respectively. came up with a new approach. First, they mixed water with a ceramic powder and some glue-like molecules, called polymer binders. Then, they poured the concoction into a little chamber that measured a few centimeters across. The scientists carefully controlled chilly temperatures at the top and bottom of the chamber, until an icy structure formed. The ice was similar to the ice that sometimes forms in frozen seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. . A closer look at the ice structure showed that it contained vertical sheets made of tiny, hexagonal hex·ag·o·nal adj. 1. Having six sides. 2. Containing a hexagon or shaped like one. 3. Mineralogy (six-sided) ice crystals. As those crystals grew, the ceramic powder and polymers gathered between the ice sheets. The scientists put this entire structure through freeze-drying to remove the ice. Heating the material to high temperatures then fused the remaining powder and polymers into solid sheets. Finally, they added a filling between the ceramic sheets to act like the protein mortar that's found in nacre. One potential application of the technique is to make a strong framework for growing new human bones to replace ones that are broken or weak from disease. Tough, pearl-like mixtures of aluminum, silicon, and titanium titanium (tītā`nēəm, tĭ–) [from Titan], metallic chemical element; symbol Ti; at. no. 22; at. wt. 47.88; m.p. 1,675°C;; b.p. 3,260°C;; sp. gr. 4.54 at 20°C;; valence +2, +3, or +4. , on the other hand, could be useful for engineers who construct machines and work with electronics. Glamorous pearl necklaces will probably never go out of style. Now, however, they hint at a suite of new technologies to come.--E. Sohn http://www.sciencenewsforkids.org/articles/20060201/Note3.asp |
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