Scientists Mimic Sea Cucumber Skin to Create Material That Rapidly Changes Rigidity

Sea cucumbers inspired the design of stimuli-responsive polymer nanocomposites with adaptive mechanical properties.

[Image courtesy of Fred Carpenter]

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 publishing in the 7 March 2008 issue of Science have developed a new material that can also switch between rigid and flexible states.

Jeffrey Capadona, a researcher at Case Western Reserve University, and colleagues extracted several nano-sized fibers, or "whiskers," many times thinner and shorter than a human hair, from a bottom-dwelling marine animal called a tunicate. When they added the whiskers to a rubbery mixture, the whiskers became firm and 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.

The team believes that this material, or one like it, might be able to improve the performance 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.

Capadona said the new material could be used to cover the tiny electrodes. 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.

The team said additional research would focus on non-chemical rigidity triggers including using light or electricity to change the material's firmness.

Kathy Wren and Benjamin Somers

6 March 2008