self healing materials

[dragon]

Way cool and lots of possible applications.

Everywhere you look, exposed surfaces are cracking. Asphalt streets are cracked, building facades are cracked, the paint on your house is cracked and flaking - the list is endless.
What if you could have a surface that repaired itself?
After all, you have a surface that heals itself - your skin. When you get a cut or a scratch, living cells deep in the living layers of your skin replace the old ones on the surface.
A team of researchers at the University of Illinois have used a technique create a polymer-based system that heals itself. An epoxy-resin base is infused with a network of interconnected channels about 200 microns in diameter. The channels are filled with low viscosity healing agent - just like your blood vessels carry healing material to cuts in your skin. This "vascularized" substrate has a solid epoxy layer deposited on top of it. A catalyst is incorporated in this solid coating.
When the coating layer is damaged, healing agent wicks from the channels through capillary action.
"Once in the crack plane the healing agent interacts with the catalyst particles in the coating to initiate polymerisation, rebonding the crack faces autonomically. After a sufficient time period the cracks are healed and the structural integrity of the coating restored. As cracks reopen under subsequent loading the healing cycle is repeated."
The idea of a "self-healing" surface is part of a larger set of ideas called "autonomous materials systems." The intent is to develop materials that can respond to their environment without additional attention from human beings. This idea has wide application not only here on Earth, but in space as well.
This week, a torn heat-resistant blanket must be repaired on the space shuttle Atlantis before it can return from orbit. The tiles on the shuttles also require inspection. What if it was possible for shuttles to have "skin" that repaired itself when cracked or damaged?

link

[DesertFly]

This sounds like an interesting idea, but how many times and how large of cracks would the material be able to "heal" before it just ran out of stuff to work with? Skin at least has the advantage of continually being replenished by minerals and nutrients we consume.