Pitt engineers model self-repairing materials

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Posted: Monday, November 25, 2013 11:50 pm

Just as starfish, deer and Mexican axoloti can regenerate body parts if injured, inanimate objects may soon be able to do the same.

A recent study suggests that phones and tables may eventually be able to repair their own cracked screens and broken legs.

Pitt engineers have developed computational models that demonstrate how a gel could allow materials to regrow and self-heal. Published in the American Chemical Society journal Nano Letters on Nov. 19, senior author Anna Balazs and three co-authors discussed the “elusive goal.” The team also included a chemistry professor from Carnegie Mellon University, Krzysztof Matyjaszewski, who worked on the computational model along with postdoctoral associate Xin Yong.

“This is one of the holy grails of materials science,” Balazs said in a press release. 

Currently, some materials are able to repair themselves locally by filling cuts or scratches.

But “there are virtually no examples of materials that can regenerate themselves,” according to the researchers.

The possibility of materials able to fully regenerate on their own holds an important implication: The lifespan of synthetic products could be indefinite.

Balazs said in a press release that the research could improve sustainability of materials. Objects wouldn’t have to be produced and purchased as often when damage occurs, saving materials and cost.

The researchers’ model was based on the biological processes found in amphibians, many of which can regenerate body parts. The materials the researchers have proposed would need to have three components: a sensor that detects damage and initiates a self-repairing reaction, a method to continue growth and a signal to stop the ongoing process.

The third step could be considered the most important — otherwise one could create an object that continues to grow, much like Alice in Wonderland, a fairytale beanstalk or a cancer cell.

The researchers used nanorods, or rods approximately one-thousandth of the width of a sheet of paper, placed in a gel surrounded by another solution. When the gel is cut, the rods will sense a change in the surface of the material, and realize that the system has changed.

The rods then spread out, expanding into the surrounding solution. The solution and rods interact with each other, causing the surface to repair itself. The growth process halts when certain particles within the outer layer have all reacted.

But if additional cuts or damage occurs, more reactive particles would have to be added to the external solution to replace those that already been used for repair.

Yong added that the nanorods were a “perfect vehicle” for modeling the reaction.

“The most beautiful, yet challenging, part was designing the nanorods to serve multiple roles,”  Yong said in a statement.

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