Mussel-inspired plastic may lead to self-repairing body armour

Scientists have developed a new mussels inspired plastic that can stretch without snapping and repair its own molecular bonds, paving the way for self- repairing body armour.
The material could also find an application in the joints of robotic arms that need to bear heavy weights but still move around, researchers said.
Mussels and some other molluscs hang onto solid surfaces using an adhesive protein and tough, plastic like fibres, which are extremely strong and can repair themselves when a few molecular bonds within them are broken, they said.
The study, published in the journal Science, found that for a mussel, these stretchy yet strong fibres come in handy when a wave hits.

Researchers from University of California, Santa Barbara in the US created a plastic with these same properties by mimicking the chemistry the mussels use.
Molecular bonds between iron and an organic compound called catechol make the material difficult to break or tear, while still allowing it to remain stretchy, they said.

The iron-catechol bonds dissipate energy from something hitting or stretching the material. These "sacrificial bonds" break, but the overall structure stays intact.
"It is like a bike helmet: if you are in a bike accident, the foam inside the helmet crushes and dissipates some of the energy. All that energy that would have gone into a skull fracture, instead goes into the helmet," Megan Valentine from University of California told 'New Scientist'.

"In our case, instead of foam we have this sacrificial bonding that protects the underlying polymer system," Valentine said.
By sacrificing the iron-catechol bonds, the material can stretch by 50 per cent. Then, once the stress is taken away, the bonds reform, making it reusable, researchers said.
Adding these bonds results in the plastic being 770 times stretchier and 58 times stronger than it is without them, they said.