Self-help for ailing structures

Abstract The notion of structures that mend themselves sounds more like an idea from science fiction than a topic for scientific investigation. Not so, say the researchers who are drawing inspiration from biological healing processes to create new composites with a built-in tool kit. This approach to materials maintenance is attracting considerable interest from the aerospace industry, given the potential value for self-repairing airplanes and spacecraft. But first, the self-help concept needs to be proven outside of the laboratory in tests that mimic likely wear and tear scenarios in the real world. It is relatively easy to illustrate the concept of a self-repairing system using familiar examples. Remember what happened when you tripped on a sidewalk as a child and grazed your knee or the last time you cut your finger. Almost at once, blood rushes to the site of the injury, leaking out where the skin has been punctured. But wait a while, and the blood oozing slowly from superficial cuts and scratches begins to clot. The clot formation slows, the bleeding stops, and, after a while, a scab forms over the damaged surface. Eventually, the scab falls off revealing a new patch of skin. Your body has healed itself, having responded instantaneously and subconsciously to the initial injury.