Moore and Researchers Develop Self-Healing Materials
Imagine a machine that, when damaged, can heal itself. This may seem like a discovery of the distant future, or a work of science fiction, but as Dr. Jeffrey Moore of the Department of Chemistry at Illinois is showing, that innovation of the future is possible today.
When a machine endures high stress for prolonged periods of time, that stress can produce microcracks which, if left unchecked, would eventually result in hazards to safety or large-scale damage. For example, if such fractures occurred in the blades of wind turbines or the fuselage of modern airplanes, serious accidents could result in injuries or death. Up to now, each of these materials has been constructed of epoxies and composites, but, because of Moore's discovery, a further component is added.
Microcapsules of a chemical called "dicyclopentadiene" are embedded in the composite material. When a microcrack occurs, the capsules located near the damage are broken as well, releasing their contents into the fissure. The dicyclopentadiene molecules fill the gap, linking to one another and forming another type of plastic that holds the crack closed and eventually — after only minutes, in fact — effectively heals the damage.
The creation of these materials has been so revolutionary that scientific and non-scientific journals alike have featured the research. What's more, the discovery earned Moore and his research colleagues a coveted place on the Scientific American's "Top Fifty Finest" list, which recognizes outstanding technological leadership by 50 individuals, teams, or companies in research, business, or policymaking each year.
This innovative discovery was not a one-step process. Moore and his colleagues have been hard at work perfecting their design to not only be practical, but also environmentally safe and economically feasible for industry. Early versions of the solution featured ruthenium-based catalysts which, while effective, were deemed impractical after further examination. A catalyst-free system was then developed to replace the ruthenium-based catalyst; however, the chlorobenzene used in this chemistry proved troublesome, owing to the potentially environmentally hazardous nature of that solvent.
Any difficulty with finding a preferred solvent did not slow Moore and graduate student Mary Caruso. They recently discovered another solution, one that not only removes any potential hazards but that also restored all of the material's original toughness. While chlorobenzene could only repair a damaged epoxy to 80 percent of its original hardness, this new solution can restore it all.
"Although we demonstrated the self-healing concept with a ruthenium-based catalyst, the cost of the catalyst made our original approach too expensive and impractical," said Moore. "Our new self-healing system is simple, very economical, and potentially robust."
Details are still forthcoming regarding the nature of Moore's newest solution, and testing is still being done. What is clear, however, is that once Moore is finished and his discovery is released, no one will ever look at a mechanical fracture in quite the same way.
Department of Chemistry
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