Liquid gallium soft robot can melt, reform into desired shape Metal Tech News - February 1, 2023
As technology begins to enter the realm of 1990s-era science fiction, researchers from Soft Machines Lab at Carnegie Mellon University have developed a miniature shapeshifting robot that can liquefy itself and reform – basically a prototype of Skynet's cool but terrifying T-1000 robot in "Terminator 2".
With assistance from Sun Yat-sen University and Zhejiang University, this liquid metal robot is based on gallium that has been embedded with magnetic nanoparticles. Since gallium has an unusually low melting point of just 85 degrees Fahrenheit (29 degrees Celsius) – enough to even melt with body temperature – it's possible to shift this soft robot between a liquid and metal without any special equipment.
The team calls this magnetoactive phase transitional matter or MPTM.
As most robots seen are of the "hard" variety, being made of solid metals and plastics. Soft robotics is an emerging field of study that seeks to build robots that are more flexible, allowing them to handle objects and navigate complex environments without the same risk of damage to the robot, as well as anyone or anything that might be nearby.
Robots that are soft and malleable enough to work in narrow, delicate spaces like those in the human body already exist, but they are unable to make themselves sturdier and stronger when under pressure or when they must carry something heavier than themselves.
To make a robot that has the advantages of both states of matter, Carmel Majidi of Carnegie Mellon University in Pennsylvania and colleagues created a robot that can not only shapeshift but also become stronger or weaker by alternating between a liquid and a solid.
The result? A millimeter-sized robot from a mix of gallium and microscopic pieces of magnetic material made of neodymium, iron, and boron – when solid, the material was strong enough to support an object 30 times its own mass; when liquid, capable of transversing most environments liquids can travel through.
To make it soften, stretch, move or melt into a crawling puddle as needed for different tasks, the researchers put it near magnets. Using customized magnetic fields would exert forces on the tiny magnetic pieces in the robot, moving them and deforming the surrounding metal in different directions.
For instance, the team stretched a robot by applying a magnetic field that pulled these gallium-neodymium-iron-boron granules in multiple directions.
Using a stronger field to yank the particles upwards, the robot would jump. Using an alternating magnetic field whose shape changes predictably over time, electrons in the robot's liquid metal would create electric currents, thereby creating a kind of actuator in the soft robot.
The coursing of these currents through the robot's body also heated it up and eventually made it melt.
"No other material I know of is this good at changing its stiffness this much," Majidi said.
In a series of experiments and capitalizing on this flexibility, the group made two robots carry and solder a small light bulb onto a circuit board. Upon reaching its target, the robot simply melted over the light bulb's edges to fuse it to the board. Afterward, electricity could then run through its liquid metal body and light up the bulb.
In another experiment conducted inside an artificial stomach, the researchers applied another set of magnetic fields to make the robot approach an object, melt over it, and finally pull it out.
In a final test, having it take the shape of a solid metal figure in the likeness of a Lego minifigure, they trapped it in a small jail. Using magnetic impulses to melt it down allowed it to flow through the bars of its captivity. Once the robot puddle dribbled into a mold, it set back into its original, solid shape outside its barred cell.
"These melty robots could be used for emergency fixes in situations where human or traditional robotic hands become impractical," said Li Zhang, a collaborator from the Chinese University of Hong Kong. "For example, a liquified robot might replace a lost screw in a spacecraft by flowing into its place and then solidifying."
While not even remotely disconcerting as Robert Patrick playing a shapeshifting death robot from the future, as long as we refrain from giving metamorphosizing metal a mind of its own, remote-controlled components or as a biocompatible extractive capsule, it seems like a fair use of its capabilities for now.
"To use them inside living stomachs, researchers must first develop methods for precisely tracking the position of the robot at every step of the procedure to ensure the safety of the patient," finished Zhang.