Scientists have devised a remarkable synthetic material that, when put under stress, can fill its own cracks--an ability that could extend the shelf life of a range of products that rely on plastic parts, including microelectronics. "Once cracks have formed within typical polymeric materials, the integrity of the structure is significantly compromised," says Scott White from the University of Illinois at Urbana-Chamgaign. "Often these cracks occur deep within the structure where detection is difficult and repair is virtually impossible." The new material White and his colleagues have created, however, begins to seal cracks as soon as they start. They describe it in today's issue of Nature.

In short, the composite consists of tiny spherical capsules, roughly 100 microns in diameter, containing a healing agent and a catalyst embedded in a matrix. "When the material cracks, the microcapsules rupture and release the healing agent into the damaged region through capillary action," White explains. "As the healing agent contacts the embedded catalyst, polymerization is initiated, which then bonds the crack face closed." When they put the new material through fracture testing in the lab, they found that it recovered as much as 75 percent of its original strength.