Changeable plastic mimics sea cucumber's trick

By Julie Steenhuysen

CHICAGO (Reuters) - A new material inspired by a defence mechanism in sea cucumbers can change easily from hard and rigid to soft and floppy, a feature that may make it suited for medical implants, U.S. researchers said on Thursday.

When wet, the material changes from a stiff plastic to a rubber-like state in seconds, and it can change back just as quickly, they said.

The material mimics a trick done by sea cucumbers. The invertebrate sea creatures can quickly change the stiffness of their skin, forming a kind of armour in response to a threat.

"We used the skin of these sea cucumbers as the basis of a new class of artificial material that can change their mechanical properties on command," said Chris Weder, a researchers at Case Western Reserve University in Cleveland, whose study appears in the journal Science.

Weder and colleagues plan to use the material in medical applications, such as pliable brain electrodes used in treatments for patients with Parkinson's disease, stroke or spinal cord injuries.

The material could be stiff to make implanting it easier, then become flexible in the water-rich brain to more closely resemble surrounding tissue.

"If you look at the tissue of the brain, it is much, much softer than the typical electrode you would implant," Weder said in a telephone interview.

Experimental studies have shown electrodes that remain stiff can degrade surrounding tissue over time. The new material is designed to overcome this mechanical mismatch, Weder said.