In another case of Nature to the Rescue, scientists have come up with a polyurethane coating that repairs itself in the sun. The secret ingredient: chitosan, which comes from the shells of crustaceans and is also used for water filtration, blood clotting and as a diet aid. The common principle appears to be that it as a binding agent, i.e. it wants to hold certain things together.
If your car is scratched and it has the chitosan-injected coating, when put in the sun the chitosan "bonds with other materials in the substance, eventually smoothing the scratch" in less than an hour. No muss, no fuss, no messy clean up. However, the magic only works once -- the coating can't repair itself in the same place twice. Researchers also haven't yet studied how wide a scratch can be before it cannot heal itself.
Nevertheless, self-repairing paint powered by the sun is still a terrific development, especially for those folks with shiny black cars on which even tiny scratches seem to scream for attention. No word on when or if it will ever be available, but the team behind it has a patent pending and is thinking about the business opportunity.