Not all that many years ago, the idea that manufactured machines, such as first-responder robots, could heal themselves spontaneously when damaged would have been something straight out of the Twilight Zone or maybe the Terminator movies. However, that once-far-fetched idea is closer to reality, thanks to researchers at Carnegie Mellon University who have created a self-healing material that spontaneously repairs itself under extreme mechanical damage, much like many natural organisms.

“This soft-matter composite material is composed of liquid metal droplets suspended in a soft elastomer,” explained the CMU researchers. “When damaged, the droplets rupture to form new connections with neighboring droplets and reroute electrical signals without interruption. Circuits produced with conductive traces of this material remain fully and continuously operational when severed, punctured, or had material removed.”

Since self-healing occurs spontaneously, these materials do not require manual repair or external heat, as do other advances in this area.

Multiple teams pursue self-healing robot skin

For example, researchers from Vrije University in Brussels, Belgium, who built a robotic hand with fingers made of a kind of elastomer, discovered that cuts and punctures could heal themselves in about a day if heat were applied to the affected area.

And researchers at the University of Colorado Boulder have developed a new type of “malleable, self-healing and fully recyclable electronic skin” that has applications for robotics. However, this “e-skin” doesn’t heal itself spontaneously. Rather, it must go through a specific process to be rehealed and ultimately recyled.

Carmel Majidi, a CMU associate professor of mechanical engineering, who heads up the Integrated Soft Materials Laboratory, said his group’s discovery is the result of approximately seven years of effort trying to figure out how to make electronics soft and stretchy and that could function as an electronic skin, or second skin, that could go on the surface of a humanoid robot or biologically-inspired robot.

Emergency response and military applications

Applications include bio-inspired first-responder robots that instantly heal themselves when damaged, he said.

“One of the big motivations is in first responder, search and rescue operations, or any kind of case where you want a robot to map and sense an environment that would be inaccessible to humans or to wheeled vehicles,” Majidi said. “You want a [soft-limbed] robot that has the properties of a snake or a quadruped that can walk over rubble or rocky terrain or obstacles and look for survivors, [for instance].”

The self-healing is important in these environments because a robot, especially a soft and squishy robot, will get damaged as it can’t control all of its interactions with the surroundings, he said.

“It’s going to scrape against a rock, it’s going to step on a nail, or it could suffer a ballistic impact if rocks fall on it,” said Majidi. “And in those types of cases, the robot, just like a natural organism, should still be able to function and complete its task — eventually, it will have to be patched up or replaced — even if it’s just for a few more hours or maybe even a few more minutes.”

The potential application of self-healing materials and advanced circuitry to bio-inspired soft robots is “interesting,” said Rian Whitton, a research analyst at ABI Research. However, he said, the real issue is that there’s not necessarily a huge commercial market for these kinds of soft robotic systems because they’re at a very embryonic stage of development.

Soft robotics still developing

“But I think it’s worth contemplating what the potential markets could be for these soft systems and where the real value is in having electronic circuitry that is self-healing,” Whitton said. “From my vantage point, these [soft robotics] technologies are at this stage going to be pretty expensive. They’re pretty difficult to implement. They’re at a very experimental stage.”

Although there might be an uptick in commercial funding and venture capital funding for these kinds of soft robotics, the main funding will come from universities, the U.S. Department of Defense, and other government agencies. So soft robotics is not really attracting a lot of commercial funding, he observed.

“In any case where the robot is likely to suffer from wear and tear or the elements and that kind of thing, like a first-responder robot, I think there is a potential application for self-repairing circuitry,” Whitton said. “You have to imagine that the military will also be very interested in this because anything that might be used for first responders is going to be designed essentially to work in a hostile environment.”

However, the soft robotics companies that have become commercially successful are companies such as Soft Robotics Inc., which builds gripping systems, Whitton said. The benefit of soft robots in this case is that they’re very dexterous and can manipulate a wider range of objects than a rigid, traditional gripper.

“What I would struggle to tell you is when this [self-healing] technology could be implemented,” Whitton said. “Soft robotics have been a topic of discussion for quite a few years now. It’s been in the public consciousness since probably about 2012, and it’s kind of grown from there. But we still really haven’t seen any commercial applications be really successful outside of soft grip assistance.”