Transparent, Self-Healing, Conducting Artificial Muscle Could Power Robots of the Future

Artificial Muscle

Researchers have created a self-healing, transparent, highly stretchable material that can be electrically activated and used to improve batteries, electronic devices, and robotics.

Researchers have developed a transparent, self-healing, highly stretchable conductive material that can be electrically activated to power artificial muscles and could be used to improve batteries, electronic devices, and robots. The development could also hold promise for revolutionary bionic devices and implants.

The findings, recently published in the journal Advanced Materials, represent the first time scientists have created an ionic conductor—a material that ions can flow through—that is transparent, mechanically stretchable, and self-healing.

"Creating a material with all these properties has been a puzzle for years. We did that and now are just beginning to explore the applications."

The potential applications of the material are vast, from allowing robots to self-heal after mechanical failure to extending the lifetime of lithium ion batteries used in electronics and electric cars to improving biosensors used in the medical field and environmental monitoring.

“Creating a material with all these properties has been a puzzle for years,” said Chao Wang, an adjunct assistant professor of chemistry who is one of the authors of the paper. “We did that and now are just beginning to explore the applications.”

The research team was inspired by wound healing in nature. They know the potential for self-healing materials is huge. Moreover, Wang developed an interest in self-healing materials because of his lifelong love of Wolverine, the comic book character who has the ability to self-heal.

Wang helped solve the problem of self-healing by using a mechanism called ion-dipole interactions, which are forces between charged ions and polar molecules that are highly stable under electrochemical conditions. He combined a polar, stretchable polymer with a mobile, high-ionic-strength salt to create the material with the properties the researchers were seeking.

The low-cost, easy to produce soft rubber-like material can stretch 50 times its original length. After being cut, it can completely re-attach, or heal, in 24 hours at room temperature. In fact, after only five minutes of healing the material can be stretched two times its original length.

Two graduate students, Timothy Morrissey and Eric Acome, working with another author of the paper, Christoph Keplinger, demonstrated that the material could be used to power artificial muscle, also called dielectric elastomer actuator. Artificial muscle is a generic term used for materials or devices that can reversibly contract, expand, or rotate due to an external stimulus such as voltage, current, pressure or temperature.

The researchers used electrical signals to get the artificial muscle to move. They were also 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. After parts of the artificial muscle were cut 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.