Plastic bleeds red and heals like human skin

Posted by Kate Taylor

A new type of plastic 'bleeds' when damaged and then heals like human skin, offering hope for those of us who can't own a gadget for five minutes without scratching it.

"Mother Nature has endowed all kinds of biological systems with the ability to repair themselves," says Professor Marek W Urban of the
University of Southern Mississippi.

"Our new plastic tries to mimic nature, issuing a red signal when damaged and then renewing itself when exposed to visible light, temperature or pH changes."

Using the new plastics, scratches in automobile fenders, for instance, could be repaired by simply exposing the fender to intense light. Critical structural parts in aircraft could warn of damage by turning red along cracks.

Previous techniques for creating self-healing plastics include seeding them with capsules that break open when damaged and release repairing compounds, or making plastics that respond to an outside stimulus — like light, heat or a chemical agent — by repairing themselves.

Urban's plastics have small molecular links or 'bridges' that span the long chains of chemicals from which plastics are made, and which break and change shape when the plastic is scratched or cracked.

The changes in shape produce a visible color change — a red splotch that forms around the defect. In the presence of ordinary light from the sun or a light bulb, the bridges reform, healing the damage and erasing the red mark.

Unlike self-healing plastics that rely on embedded healing compounds that can self-repair only once, Urban's version can heal itself over and over again. The  team's now working on incorporating the technology into plastics that can withstand high temperatures.