


Bleeding is one of the ways your body alerts you and others to an injury. This material works the same way. Sure, we've seen smart, self-healing materials like this before, but there aren't that many materials that can heal themselves and weep like a freshly skinned knee.

That means that — at least for now — some of the most promising applications for these bleeding plastics are in materials that could benefit from a damage warning system, like automobile fenders, or the structural components on airplanes.

"Mother Nature has endowed all kinds of biological systems with the ability to repair themselves," explained researcher Marek W. Urban, who described the new plastics at this week's National Meeting & Exposition of the American Chemical Society.

He continues:



According to a release issued by the American Chemical Society, the "red signal" that Urban mentions appears when the links (or "bridges") connecting the plastic's molecular chains are broken. The term "link" may call to mind the concept of "cross-linking," whereby the molecular chains of a polymer become bound to one another by strong, permanent, and orderly bonds; but when we spoke with Urban on the phone, he explained that his team's system does not rely not on a cross-linked system.

"Our material is what's called a thermoplastic," he tells io9 — which means no cross-links are formed during the creation of the plastic. In contrast, plastics that do form cross-links are called "thermosets." The key difference between the two, explains Urban, is that once a thermoset cures, its structure is basically set for life, which makes it less-than-optimal for self-healing applications. "Thermoplastics, however, you can heat and reshape however you want," Urban explains. [See here for a good introduction to the differences between thermoset and thermoplastic materials]

When we pressed Urban to share more details with us about the bleeding capabilities of his team's latest plastic, he politely declined to go into specifics on the science, explaining that it would have to remain under wraps until a later date. (In other words: there are publications in the works.) For now, however, it's simultaneously weird and comforting to think that there could be bleeding cars and airplanes right on the horizon. [ACS]