FEB. 15 Champaign, Illinois–University of Illinois researchers have developed a synthetic material that can heal itself when it becomes cracked or broken. The material, consisting of a microencapsulated healing agent and a special catalyst embedded in a structural composite matrix, could increase the reliability and service life of thermosetting polymers used in a wide variety of applications ranging from microelectronics to aerospace.

The ability to self-repair and restore structural integrity may be used to extend the lifetimes of polymer composite circuit boards, where microcracks can lead to both mechanical and electrical failure.

“Once cracks have formed within typical polymeric materials, the integrity of the structure is significantly compromised,” says Scott White, a UI professor of aeronautical and astronautical engineering. “Often these cracks occur deep within the structure where detection is difficult and repair is virtually impossible.”

In the new material, however, the repair process begins as soon as a crack forms. “When the material cracks, the microcapsules rupture and release the healing agent into the damaged region through capillary action,” explains White. “As the healing agent contacts the embedded catalyst, polymerization is initiated which then bonds the crack face closed.”

One of the many challenges the researchers faced in developing the material was obtaining the proper size of microcapsules. They currently use spheres about 100 microns in diameter. Larger spheres could have weakened the matrix, White said, and work continues on creating ever-smaller capsules.