A new polymer material that fixes its own cracks could be a step toward self-healing medi­cal implants or self-­repairing materials for use in airplanes and spacecraft. It consists of an epoxy polymer layer containing tiny catalyst particles, deposited on a substrate containing microchannels filled with a liquid.

When a crack in the polymer layer spreads to the micro­channels, the liquid flows out and comes in contact with the catalyst, says Nancy Sottos, a professor of materials science and engineering at the University of Illinois at Urbana-­Champaign and one of the researchers who led the work. Ten hours later, the liquid ­solidifies into a polymer.