'Self-healing' plastic revealed
A "smart" plastic which heals itself could make light work of simple car repairs.
The polymer, composed of chain-like molecules, spontaneously mends small scratches and scuffs when exposed to ultraviolet light. It takes less than a minute for the material to liquefy into a form that fills crevasses and gaps before turning solid again.
Experts, whose research is published in the journal Nature, believe the healable material could be used in motor vehicle paints, varnishes for floors and furniture, and many other applications.
Unlike conventional polymers made up of long molecules with thousands of atoms, the material has smaller elements assembled into chains by a type of "molecular glue".
When exposed to intense ultraviolet light, the structures become temporarily "unglued". As a result, the solid material turns into a flowing liquid. Once the light is switched off again, the material reassembles and solidifies.
Lead researcher Professor Stuart Rowan, from Case Western Reserve University in the US, said: "These polymers have a Napoleon complex. In reality they're pretty small but are designed to behave like they're big by taking advantage of specific weak molecular interactions."
In tests, scratches filled up and disappeared much like minor cuts in the skin that heal without a trace. Researchers were also able to scratch and repair the same place repeatedly.
Several different versions of the polymer were investigated to find the best combination of mechanical properties and healing ability.
Previous "smart" materials have relied on heat to trigger self-repairs.
"By using light, we have more control as it allows us to target only the defect and leave the rest of the material untouched," said Mark Bunworth, another member of the Case Western Reserve research team.