The illustration shows new self-healing material. (Credit: University of California Riverside)
Inspired by Wolverine from X-Men, a California based scientist is one step closer to developing the self-healing powers synonymous with his favorite Marvel character.
Scientists from the University of California, Riverside, led a team in developing a transparent, self-healing, highly stretchable conductive material that could be electrically activated to power artificial muscles and also improve batteries, electronic devices and robots.
The material is said to be a soft-rubber-like material that is low-cost and easy to produce. It can stretch 50 times its original length and after being cut it can completely re-attach or heal in 24 hours at room temperature.
This represents the first time scientists have been able to create ionic conductors, meaning materials that ions can flow through that is transparent, mechanically stretchable and self-healing.
Ionic conductors also play key roles in energy storage, solar energy conversion, sensors and electronic devices.
Chao Wang, an adjunct assistant professor of Chemistry and co-author of the paper, explained the breakthrough.
“Creating a material with all these properties has been a puzzle for years,” Wang said in a statement. “We did that and now are just beginning to explore the applications.”
Wang became interested in self-healing properties because of his affinity for Wolverine.
Some of the realistic applications for the material include giving robots the ability to self-heal after mechanical failure, extend the lifetime of lithium ion batteries used in electronics and electric cars and improve biosensors used in the medical field and environmental monitoring.
Christoph Keplinger, an assistant professor at the University of Colorado Boulder and co-author of the study, previously demonstrated that stretchable, transparent, ionic conductors can be used to power artificial muscles and can create transparent loudspeakers—devices that feature several of the key properties of the new material but none of those devices additionally had the ability to self-heal from mechanical damage.
The main difficulty scientists have had is the identification of bonds that are stable and reversible under electrochemical conditions.
Self-healing polymers make use of non-covalent bonds, which is problematic because those bonds are affected by electrochemical reactions that degrade the performance of the materials.
However, Wang was able to utilize ion-dipole interactions, which are forces between charged ions and polar molecules that are highly stable under electrochemical conditions. Wang was able to combine a polar, stretchable polymer with a mobile, high-ionic-strength salt to create the material with the properties the researchers were seeking.
The dielectric elastomer actuator or artificial muscle developed by Timothy Morrissey and Eric Acome, two graduate students working with Keplinger, is three individual pieces of polymer that are stacked together.
The top and bottom layers are the new material developed by Wang’s team, which is able to conduct electricity and is self-healable. The middle layer is a transparent, non-conductive rubber-like membrane.
The researchers used electrical signals to get the artificial muscle to move, similar to how a human muscle like the bicep moves when the brain sends a signal to the arm.
The researchers were able to demonstrate that the ability of the new material to self-heal can be used to mimic a preeminent survival feature of nature—wound-healing. They proved this by cutting the artificial muscle into two separate pieces. The material healed without relying on external stimuli and the artificial muscle returned to the same level of performance as before being cut.
The study was published in Advanced Materials.
