self healing material
May 10, 2014

Engineers Develop Self-Healing Material Capable Of Fixing Larger Cracks And Holes

[ Watch the Video: Regenerating Plastic Grows Back After Damage ]

redOrbit Staff & Wire Reports - Your Universe Online

Taking inspiration from the way in which blood clots can help repair wounds, engineers from the University of Illinois have developed a new regenerating plastic capable of regrowing material to fill in cracks and holes.

According to BBC News reporter James Morgan, previous research in the field of self-healing materials could only focus on microscopic cracks. This new plastic polymer, however, is capable of automatically fixing holes 3 cm wide – 100 times larger than before.

“For decades scientists have dreamed of plastics that heal themselves like human skin,” Morgan said. “Cracks in water pipes and car bonnets would seal up. Satellites could repair their own damage. Broken electronic chips in laptops and mobile phones would spontaneously sort out their own problems.”

Now, lead researcher Scott White, a professor in the university’s Autonomous Materials Systems (AMS) Group, and his colleagues have brought that vision one step closer to fruition. Their research appears in the May 9 edition of the journal Science.

On Thursday, White said in a statement that his team was able to successfully demonstrate “repair of a nonliving, synthetic materials system in a way that is reminiscent of repair-by-regrowth as seen in some living systems.”

“Such self-repair capabilities would be a boon not only for commercial goods – imagine a mangled car bumper that repairs itself within minutes of an accident – but also for parts and products that are difficult to replace or repair, such as those used in aerospace applications,” the university noted.

The material is able to regenerate thanks to the reaction produced when two liquids are mixed, explained Jacob Aron of New Scientist. One of the fluids contains molecules that are long and thin, while the other contains three-sided ones. When they mix, the molecules in those fluids essentially create a scaffold similar in structure to a blood clot.

Those liquids turn into a thick gel that fills damaged areas after just a few minutes, and then other substances within the fluids cause them to harden over the course of a few hours. The researchers tested their concept by running two separate streams of each liquid through a plastic square.

Next, they punctured the plastic in order to form a hole that was 4 mm in size, that had 35 mm worth of cracks surrounding it, and that also ripped open the fluid capillaries. Devices on the square squirted the fluids into those pathways, and once they mixed, they filled the hole and the cracks in just 20 minutes time. After three hours, the materials had hardened to create a patch approximately 60 percent as strong as the original material.

Last month, White and his associates successfully demonstrated for the first time that repeated healing was possible in a fiber-reinforced composite system. The research team developed 3D vascular networks, or patterns of microchannels filled with substances that could mix and polymerize in order to heal damaged materials. Their vascularization method allowed them to adapt self-healing polymer techniques to fiber-reinforced composites.

The new study builds upon that research, according to co-author Nancy Sottos, a professor of materials science and engineering at the University of Illinois. She said that the vascular delivery technique allowed the engineers to “deliver a large volume of healing agents,” which in turn made it possible for large damaged areas to be repaired. It also allows for the same material to be repaired more than once.

“The team demonstrated their regenerating system on the two biggest classes of commercial plastics: thermoplastics and thermosets,” the university added. “The researchers can tune the chemical reactions to control the speed of the gel formation or the speed of the hardening, depending on the kind of damage. For example, a bullet impact might cause a radiating series of cracks as well as a central hole, so the gel reaction could be slowed to allow the chemicals to seep into the cracks before hardening.”