Material Progress

Designers have crafted new structures ranging from nanorods to mimics of mother-of-pearl

Extraordinary properties emerge as scientists manipulate construction blocks at the nanometer scale. Diamond nanorods discovered by Natalia Dubrovinskaia of the University of Bayreuth in Germany and her colleagues pack together into a dense form of carbon that is harder than diamond. Potential industrial applications for materials made from nanorods include the cutting and polishing of alloys and ceramics.

Carbon was also the material chosen by Pulickel M. Ajayan and his colleagues at the Rensselaer Polytechnic Institute to create superresilient springs. The researchers used a foam made of carbon nanotubes to devise springs that combine the properties of stiffness and compressibility. Repeatedly compressing a cushion typically squashes it, making it lose its springiness. But the nanotube foams remained elastic even after 10,000 squeezes, a property that could make the material suitable for artificial joints or vibration dampeners.

Scientists draw inspiration from nature to come up with breakthrough materials. Modern ceramics are strong but brittle, whereas mollusk shells exhibit strength while retaining intrinsic toughness because of their finely layered mother-of-pearl, or nacre. Antoni P. Tomsia of Lawrence Berkeley National Laboratory and his colleagues found they could mimic nacre just by freezing a watery suspension loaded with hydroxyapatite, bone's mineral component (left). They built a multilayered nacrelike material that might find use in artificial bone and joints or in tissue regeneration.

Research that took inspiration from the natural world may also prove useful to the electronics industry, which often requires high temperatures and harsh acids or bases to produce thin films of silicon or other semiconductors. Daniel E. Morse of the University of California, Santa Barbara, found that by putting enzymes that mimic those of marine sponges onto gold surfaces, his team could create templates for growing semiconductor films. Inspiration from a lowly marine sponge may eventually yield more powerful batteries.

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