Self-healing materials research continues to benefit from interdisciplinary approach

8/14/2013 If you have any questions about the College of Engineering, or other story ideas, contact Mike Koon, writer/editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-1256.

Professors Nancy Sottos and Scott White have embraced that concept at the Urbana-Champaign campus for nearly two decades as innovators in self-healing materials research.

Written by If you have any questions about the College of Engineering, or other story ideas, contact Mike Koon, writer/editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-1256.

As interdisciplinary research on college campuses grows, the University of Illinois continues to do it well. Professors Nancy Sottos and Scott White have embraced that concept at the Urbana-Champaign campus for nearly two decades as innovators in self-healing materials research.

Both came to campus during the mid-1990s. White is in aerospace engineering and Sottos in materials science and engineering. The two shared interest in composite materials and had offices in the same hallway at Talbot Laboratory.

“Our combined interest in composite materials gave us a basis to have a conversation, but interdisciplinary research doesn’t work unless you’re friends at heart to begin with,” White said. “There is a lot of trust that you have to have in order for this to work over the long term. You find that at the core of our teaming. We’ll often go down to the café to have lunch and over conversation, something will come out that leads to the next big advancement. It’s not forced, it’s just organic.”

 “What sets Illinois apart from both a computational and experimental standpoint is that it has had this long history of shared resources and great facilities (MRL, Beckman Institute, Coordinated Science Lab, NCSA),” Sottos said. “That induces cross-disciplinary investigations because it encourages professors to talk to other people.

Nancy Sottos, Scott White and Jeff Moore have collaborated in self-healing research for over a decade.
Nancy Sottos, Scott White and Jeff Moore have collaborated in self-healing research for over a decade.
Nancy Sottos, Scott White and Jeff Moore have collaborated in self-healing research for over a decade.

At the beginning, Sottos and White set out to collaborate on predicting defects in composite materials and it soon turned into investigating whether they could actually produce a synthetic material that heals itself.

“At the time, the heart of the smart materials field was the idea of building within a material the ability to react to its environment,” White recalled. “We asked the question, ‘Is there a way to make a material that would at least be tolerant of defect if not out right heal them like the body does?’”

Over the course of their research, they have needed other professors, including many from other departments to advance. Fellow aerospace colleague Philippe Geubelle was brought in early to provide expertise in computational modeling. The trio along with a pair of master’s students had brainstorming sessions to evaluate concepts after securing a small grant from the Army Corps of Engineers.

“It was actually a lot of fun,” Sottos said. “We used to each have homework, some of which I still have. Based on some calculations and some preliminary experiments, we ranked some concepts and determined capsules would be a good way of delivering some healing chemistry. That concept was motivated by a talk I heard where someone was using capsules like they do in the cosmetic industry and they were really good at toughening the material. Scott also knew about all the carbonless paper work on capsules.”

Although they had some success in getting materials to self-heal, their research hit a roadblock when they realized they needed more chemistry expertise. That’s when White approached chemistry professor Jeff Moore to see if he would be interested in joining the team.

“That pursuit was kind of legendary,” Sottos said. “Scott contacted him and let’s just say he was persistent. When Jeff came on board, we got another small set of funding.”

“From that point forward, the accelerator has been down and we have made rapid progress in a number of different areas,” White said.

Another early challenge was being able to find a lab that had all the resources they needed in one spot. Sottos credits former Beckman directors Jiri Jonas and later Pierre Wiltzius for finding space in the building for the research team.

“My lab in Talbot was not set up to do chemistry, but because this was a fledgling project and not yet on the national scene, we weren’t sure if we could convince anyone on campus to provide us what we needed. Getting Beckman behind it allowed us to get space for materials chemistry and materials processing in a controlled environment.”

With the Beckman space secured, the team was able to gather enough data to have its first paper published in Nature magazine in 2001. Fortuitously, the findings coincided with the cracking of the human genome, which was the cover story of that Nature magazine.

“There were a lot of reporters waiting for this issue to come out,” Sottos recalled. “A reporter from the Washington Post saw this little story on self-healing materials, contacted us, and put us on the front page of the paper.”

The research collaboration has been a trendsetter in the industry ever since where self-healing materials research has blossomed into a worldwide research concern. Today groups are pursuing this from China to England to the Netherlands, Spain, and Germany.

Their results have not only been researched based, but also through the many talented students the lab is producing. Those include Michael Kessler, who received his PhD in Theoretical and Applied Mechanics from Illinois in 2002 and is the new director of Mechanical and Materials Engineering at Washington State University; and Eric Brown, a 2003 PhD recipient in TAM who serves as the Deputy Group Leader for the Neuron Science Technology, Physics Division at Los Alamos National Laboratory.

“The students here have a lot of benefits because they work with lots of types of students,” Sottos said. “They have to work in teams and give a lot of presentations, including to people outside their discipline.”

"My experience as a graduate student in the late 1990s and early 2000s, working with Scott White, Nancy Sottos, and their co-workers, on the development of self-healing materials, was instrumental to my future career in academia,” Kessler said. “Their example taught me to how to reach across traditional disciplinary boundaries to tackle big problems by combing fields such as organic chemistry, solid mechanics, and processing science."

“The scientific knowledge and personal growth I gained working with Nancy and Scott as a graduate student continue to permeate everything I do in my career through developing my own programs of research, managing large research organizations, and leading international scientific programs,” Brown added.

White, Sottos, Moore and Paul Braun and founded Autonomic Materials, Inc., in 2007 to help market the products to among others the marine, automotive and oil and gas industries. They are actively developing commercial self-healing coatings for use across a broad spectrum of industries.

While the team was successful in producing materials that self-heal, they switched gears from a capsule-based model to a vascular-based healing system.

“In a capsule-based system, once you break a capsule and you release its healing agent, it’s depleted of the supply of healing agent in that area of the material,” White explained. “In a vascular-based approach, you should be able to resupply and recirculate healing agents indefinitely.”

The new approach meant more experts brought to the table, including Jennifer Lewis from materials science and engineering and Jonathan Freund and Kenneth Christensen from mechanical science and engineering.

Their next breakthrough came in 2007 when they published their work on successful repeated healing using this vascular approach. Over the past three years, they have tried to apply the same concepts to batteries and electrical energy storage systems.

Self-healing materials
Self-healing materials
“Now the defects are not in load-carrying capability, rather it is in energy storage capability or electrical conductivity,” White said. “We’ve been incorporating microcapsules into batteries are also working on a project that releases a thermally triggered material to automatically shut a battery down before it erupts into a fire.”

They have also been focused on regeneration and being able to fill really large damaged volumes and hope to to publish those findings before the end of the year.

“We are trying to be inspired by biology and replicate some of the major systems and processes,” White explained.

“What happens if there is material gone, like that from a bullet hole,” Sottos added. “Surface tension and gravity wouldn’t let you fill that hole. Instead, we have a system that is gelling just enough resin that can keep the material soft, but a significant time later, polymerize. It’s an unusual chemistry.”

As progress continues to be made by Sottos and White and other members of the Autonomous Materials Research Laboratory, they will be continue to benefit from the interdisciplinary environment fostered at the University of Illinois.

“I can’t oversell the benefit of Beckman,” White said. “The proximity of our offices to our student offices and the laboratories is fundamental to seeing something like this work. It’s amazing to see an aerospace engineer standing right next to a chemist doing the same experiment and the different approaches they bring, which leads to insight that wouldn’t be there unless they were able to work effectively together. That has been crucial to the success of this whole endeavor.”


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This story was published August 14, 2013.