Self-repairing surface based on crab skeleton

US scientists have come up with a new way to solve problem trolley-scrapes acquired in the supermarket car-park - a self repairing surface triggered by UV.

Writing in this week'sScience, University of Southern Mississippi research duo Biswajit Ghosh and Marek Urban set out the clever - and elegantly simple - chemistry behind what they hope will form the next generation of car paints.

The key chemicals are a polyurethane polymer within which is embedded a molecular carbon ring structure known as an oxetane ring which is itself linked to a chemical called chitosan. This latter molecule is the same material that crabs and shrimps use to fashion their exoskeletons.

This chemical combination can be applied to a surface where it forms a stable coating. But if the material is scratched, as soon as UV light falls upon it the traumatised area stitches itself back together with near-invisible results.

The trick works because the oxetane ring is highly strained and readily breaks open creating active sites that can be cross-linked back together by reactive chemicals produced when UV hits the mixture. As a result, the researchers have found, after just 30 minutes in the Sun a scratched surface would have completely healed.