“The idea of creating a material that can automatically heal itself is not novel, but applying that idea to additive manufacturing is,” said Dr. Kevin Hart, assistant professor in the Mechanical Engineering Department, in reference to his latest research project.  

Beginning in fall 2020, Hart worked with five undergraduate students investigating the best way to implement self-healing in a 3D-printed material. From that work, Hart secured funding for a Summer Faculty Development Grant from B´ÎÔª for his project, “Development of Self-Healing, Additively Manufactured Polymeric Material.” Part of the grant funds were used to support a summer student worker, Jack Turicek, to assist with the research.

While many research projects have focused on pursuing stronger 3D printed parts, Hart’s research shifted away from making stronger parts to discovering how they can self-repair to restore their lost mechanical properties. “This is the way biological systems work, and we are looking to mimic biological ideas here in synthetic materials,” said Hart.  

Hart explained the project began with embedding a vascular network inside of an additive manufactured polymer, which is a 3D-printed material. “The vascular network in the material served as a pseudo blood-vessel with the ability to carry liquid healing agents to damaged areas of the material,” said Hart. “Using laboratory testing, we fabricated samples, introduced a controlled damage event, then used delivery of liquid healing agents to the site of damage to execute the healing reaction.”  

Life-cycle of a self-healing additively manufactured polymer. Damage in the material causes solvents to leak into the crack, healing the material back to its original state, ready for future healing, should damage occur again.  

After three days at room temperature, the team re-tested the material to quantify the health that occurred. “In our testing, we were able to recover 100% of the material’s original mechanical properties using our methods. That means that the region that was damaged and then healed was actually stronger after this healing event,” said Hart.  

The project was highly successful. The team is in the midst of writing a publication on the work and planning to submit it to Additive Manufacturing, a peer-reviewed journal that provides high quality research papers and reviews. Hart also plans to present the work at the 2022 Society for Experimental Mechanics Annual Meeting in Pittsburgh in June 2022.  

Hart first began working on self-healing fiber-reinforced composite materials when he was a graduate student, however this was his first time serving as an advisor to a set of students who were responsible for performing the hands-on work. While shifting to advising and allowing students to execute the majority of the work was initially a challenge for Hart, it benefited all parties in the end. “This paid off in the long-run, allowing the students to learn more about the research process while still resulting in a successful project,” said Hart.  

Students who contributed to this project include Kyle Holland, Dylan Kalchik, Eirene Kowal, Jonathan Stowe and Turicek, who all graduated in May 2021 with a B.S. in Mechanical Engineering.