A biopolymer that switches from rigid to flexible has been created by Case Western University researchers. It mimics the structure of sea cucumbers, which are able to change their skin from soft and flexible (for getting through narrow spots) to hard and rigid (armor to protect them from predators).

It is known that sea cucumbers have skin composed of very fine cellulose fibers. When attacked, surrounding cells secrete molecules that cause these "whiskers" to bind together, forming a kind of protective armor. When relaxed, other cells release plasticizing proteins to loosen the fibers, allowing the creatures to flow easily through crevices.

Researchers isolated the cellulose fibers from the surface of creatures similar to sea cucumbers. The researchers then combined the fibers with a rubbery polymer mixture. The fibers formed a a kind of mesh through the body of the material, reinforcing the softer polymer. The fibers hold it together, creating an inflexible material. "It's like a three-dimensional web in which these nanofibers overlap at certain points, and wherever they overlap, they stick to each other," say researchers.

It is hoped that this rigid-yet-flexible material could be used in biomedical applications, like implantable electrodes that could record brain activity over long periods of time, without the scarring produced by conventional metal electrodes. This material is a variation on the idea of shear-thickening fluids used in applications as varied as body armor and rehabilitative exoskeletons.

Readers who appreciate science fiction films may recall the wet wired brain implants used in the 1995 movie Johnny Mnemonic; some sort of flexible/rigid biopolymer would be just what the doctor ordered.

(This Science Fiction in the News story used with permission of Technovelgy.com.)