Nanoplastic shifts from hard to soft and back again

Scientists have created a breakthrough substance that can change in seconds when exposed to liquid, shifting from hard plastic to soft and back again, and that has a wide range of potential medical applications.

The material -- inspired by the skin of sea cucumbers -- has astounding "mechanical morphing characteristics," according to an article published in the latest issue of Science.

Researchers said a plethora of possible biomedical applications exist for the malleable new material, including as part of "artificial nervous systems" for patients with Parkinson's disease, stroke or spinal cord injuries.

Sea cucumbers, found on ocean floors around the world, have leathery skin, an elongated, cucumber-like shape, and a consistency that can be either gelatinous, stiff and rigid, or anything in between.

This "switching effect" in the tissue of the sea cucumber is derived from a distinct nanocomposite structure in which highly rigid collagen nanofibers are embedded in a soft connective tissue.

Now the school of engineering at Case Western Reserve University and researchers at the Louis Stokes Cleveland Department of Veterans Affairs Medical Center have succeeded after years of effort in mimicking the unusual architectural structure of the sea creatures.

"These creatures can reversibly and quickly change the stiffness of their skin. Normally it is very soft but, for example in response to a threat, the animal can activate its 'body armor' by hardening its skin," said Jeffrey Capadona, associate investigator at the VA's Advanced Platform Technology (APT) Center.

With the sea cucumber as their model, the scientists unveiled a radically new approach for developing polymer nanocomposites which alter their mechanical properties when exposed to certain chemical stimuli.

"We can engineer these new polymers to change their mechanical properties -- in particular stiffness and strength -- in a programmed fashion when exposed to a specific chemical," said Christoph Weder, a professor of macromolecular science at Case Western Reserve, and a senior author on the article.

Stuart Rowan, professor of macromolecular science at Case Western Reserve, said: "The materials ... were designed to change from a hard plastic -- think of a CD case -- to a soft rubber when brought in contact with water."

Source: discovery.com