Bell Labs scientists find optics in marine creatures

Aug. 23, 2001--The surprising discovery that brittlestars use calcitic crystals to act as optical detectors, in addition to providing skeletal support, was made by an international multidisciplinary team of researchers.

Scientists from Lucent Technologies' (NYSE: LU) Bell Labs have discovered that chalk-like calcite crystals in the skeletons of marine creatures known as brittlestars have a remarkable dual function, acting as armor as well as optical receptors for an all-seeing compound eye. They say that studies of this novel multifunctional biomaterial may lead to better-designed optical elements for telecommunications networks.

The surprising discovery that brittlestars use calcitic crystals to act as optical detectors, in addition to providing skeletal support, was made by an international multidisciplinary team of researchers, comprising scientists from Bell Labs, the Weizmann Institute of Science in Israel and the Natural History Museum of Los Angeles County, and will be described in an article to be published in the August 23 issue of Nature magazine.

"This is an excellent example of something we can learn from nature," said Federico Capasso, physical research vice president at Bell Labs. "These tiny calcite crystals are nearly perfect optical microlenses, much better than any we can manufacture today."

Brittlestars, also known as serpent stars, are marine invertebrates that usually have five thin long arms emanating from a small, disk-shaped body. They belong to the phylum of echinoderms, which also includes starfish, sea urchins and other related classes of marine organisms.

The analysis of bony structures in the arms of the brittlestar Ophiocoma wendtii showed the presence of a regular array of spherical microstructures that look like lenses. Experiments subsequently showed that these microstructures, which are absent in closely related but light-indifferent species of brittlestars, were indeed sophisticated optical elements that have the optimal design for focusing light.

The lenses focus light about 5 microns below their surface. Nerve bundles running through the skeleton underneath the lenses are thought to pick up the light signal. Acting together, thousands of calcite crystals form a kind of primitive compound eye that covers much of the organism's body, and researchers think this must be useful in detecting and escaping from predators.

The calcite microlenses expertly compensate for birefringence and spherical aberration -- physical effects common in lenses that distort light -- and scientists hope to mimic nature's success and design microlenses based on the brittlestar model. Such biomimetic lenses may prove useful as components of optical networks, and in chip design, where they could potentially improve optical lithography techniques.

In an accompanying commentary in the issue of Nature, independent expert Roy Sambles of the University of Exeter, UK, wrote, "Once again we find that nature foreshadowed our technical development."

Other researchers involved in the research were Alexei Tkachenko of Bell Labs, Steve Weiner and Lia Addadi of the Weizmann Institute of Science and Gordon Hendler of the Natural History Museum of Los Angeles County.

About Bell Labs:

Bell Labs is an R&D organization dedicated to communications technologies, including transistors, digital networking and signal processing, lasers and fiber-optic communications systems, communications satellites, cellular telephony, electronic switching of calls, touch-tone dialing, and modems. For more information, visit www.bell-labs.com.

About Lucent:

Lucent Technologies, headquartered in Murray Hill, N.J., USA, designs and delivers networks for communications service providers. For more information, visit www.lucent.com.

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