Unless it’s a severe, a simple cut on your arm doesn’t require a trip to the doctor’s office. It’s prudent to apply an antibiotic ointment and a clean bandage, but your body can heal itself just fine without them most of the time. Even bone fractures can heal completely on their own, and many animals are capable of regenerating entire limbs. But our robots don’t possess that same self-sufficiency, which means they need to come back to us for repairs. These self-healing liquid metal tendons could make it possible for robots to repair themselves and then continue on with their work.
The most obvious comparison we can make is to the T-1000 robot, originally portrayed by Robert Patrick in 1991’s Terminator 2: Judgment Day. In that movie, the entire robot is made from a fictional amorphous semi-liquid metal that could form into new tools or immediately repair damage. While that kind of technology is pure fantasy, robots can take advantage of metallic alloys to heal themselves after being damaged. It may not be as dramatic as an unstoppable movie robot, but it is very practical.
This research comes from a team at the University of Tokyo’s JSK Laboratory, and was presented at IROS 2019. They have developed a self-healing mechanical fuse that can be integrated into just about any robot design. Like its electronic counterpart, this mechanical fuse is designed to be the first point of failure. It’s relatively weak, and so it will fracture before the other components in a robot's leg, for example. Once it does, the robot can stop moving temporarily and repair that mechanical fuse in order to get back to work within about 30 minutes.
The mechanical fuse has two solid halves that are made from a strong material, like steel. Those are joined by simple springs and magnets. An internal cavity formed by the two halves is then filled with a metal alloy that has a low melting point. A cartridge heater is capable of liquefying that alloy, which then fills in the cavity. After it cools, the entire mechanical fuse becomes rigid and can act as a structural component again. If the robot takes another tumble, that mechanical fuse will be the first thing to break and the alloy can simply be melted for another repair. This wouldn’t be a perfect solution for every scenario, but it would help robots run longer without needing repairs from humans.