The Autonomous Materials Systems Group at the Beckman Institute for Advanced Science and Technology, Urbana, Ill., recently devised a way to identify microscopic damage in polymers and composites by incorporating microcapsules containing materials that fluoresce under stress.
“We’ve developed microcapsules that are colorless and non-fluorescent when intact,” said Maxwell Robb, Beckman Institute Postdoctoral Fellow and a lead author of “A Robust Damage-Reporting Strategy for Polymeric Materials Enabled by Aggression-Induced Emission,” recently published in ACS Central Science.
“We can embed them into materials, and when damage occurs, the microcapsules will release their payload and become fluorescent, indicating that repair is needed,” says Wenle Li, a postdoctoral research associate and co-first author.
“Autonomous indication of small cracks has potential to make structures safer and more reliable by giving time to intervene and repair or replace the damaged region prior to catastrophic failure,” said Nancy Sottos, professor of materials science and engineering, and one of the authors.
The new method uses a type of fluorescence called aggregation-induced emission (AIE), which becomes brighter as the indicator solidifies from solution, and is visible under ultraviolet light. The unique mechanism of indication, which relies on a physical change of state instead of a chemical reaction, enables excellent performance in a wide variety of materials and for visualizing different types of damage.
“The elegance of this system lies in its versatility as well as its sensitivity,” says Dr. Li. “We can easily visualize a fluorescence signal resulting from mechanical damage as small as two microns.”
The research is funded by BP, which is interested in coating oil and gas pipelines with a polymer coating that will be able to indicate damage. The goal is to target damage at its earliest stage to prevent further deterioration, improve safety and reliability, and reduce life cycle costs associated with regular maintenance and inspection.
http://beckman.illinois.edu/news/2016/08/ams-aie
