Designed by a team led by professors Nancy Sottos and Scott White, the polymer contains epoxy resin microcapsules filled with a light-yellow pH-sensitive dye.
As long as no damage occurs, those capsules remain intact. However, should a crack form (as small as 10 micrometers in width), the capsules in that area burst and release the dye. That dye chemically reacts with the epoxy, changing from yellow to bright red in color. The larger the crack, the greater the amount of dye reacts, and the more pronounced the color-change.
According to the researchers, the polymer has been successfully tested on materials including metal, glass and other polymers. It's also reasonably inexpensive, as it only needs to be composed of five percent microcapsules in order to work effectively.
Along with other possible applications, they're now looking at incorporating the polymer into a self-healing plastic that they previously created. In that case, an initial color-change would indicate that a crack had formed, while a secondary change would indicate that it had subsequently healed.
Source: gizmag.comAdded: 19 January 2016