As Professor Sottos puts it: "Polymers are susceptible to damage in the form of small cracks that are often difficult to detect. Even at small scales, crack damage can significantly compromise the integrity and functionality of polymer materials."
It works on multiple kinds of polymers that can coat metals, other polymers and glass. Importantly there's no sign of degradation: the capsules will stay intact until actual cracks or damage happen. And compared to other techniques, it's not too expensive, either, given the high investment needed for space vehicles. "A polymer needs only to be 5 percent microcapsules to exhibit excellent damage indication ability," Sottos said. "It is cost effective to acquire this self-reporting ability." The researchers are now looking to pair this damage signaling with self-healing systems, meaning future materials could not only notify engineers of damage, but also attempt to repair themselves.