Sea-cucumber skin inspires new material

Scientists have long been amazed by the skin of a sea cucumber, which can switch from stiff to floppy, or vice versa, in mere seconds in order to help the animal defend itself against predators.

Inspired by this quick-change act, researchers have developed a new material that can also switch between rigid and flexible states. They hope that this material, or one like it, might someday be used as part of medical devices that are implanted inside the body.

For example, tiny electrodes implanted into the brain are sometimes used to treat Parkinson’s disease, stroke and spinal chord injuries. But, they can become less effective with time as the body creates scar tissue around the hard implant.

Jeffrey Capadona of Case Western Reserve University and colleagues would like to cover the electrodes in this new material. The outer layer would be stiff at first, allowing the device to be implanted. But, once inside the body, the material would become soft, more like the surrounding brain tissue.

Dr. Capadona’s team started with nano-sized fibers, or “whiskers,” many times thinner and shorter than a human hair, that came from a ground-dwelling sea creature called a tunicate. When they added the whiskers to a rubbery mixture, the whiskers linked up into a network within the mixture.

Dipping the material in a special chemical solution softened the material, because it disrupted the bonding between the fibers. When the treatment evaporated, the whiskers reformed their network, making the material stiff again.

These findings appear in the 7 March 2008 issue of the journal Science.

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