Study of remarkable optics in marine creatures may help development of microlenses for optical networks

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24 October 2001 News

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

The lenses focus light about 5 mm 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. 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. "Biomimetics builds on nature's expertise," said John Rogers, Director of Nanotechnology Research at Bell Labs. "In this case, a relatively simple organism has a solution to a very complex problem in optics and materials design."

www.bell-labs.com

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Study of remarkable optics in marine creatures may help development of microlenses for optical networks

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