A millimeter-sized robot made of liquid metal and microscopic magnetic grains can stretch, move or melt on command. Such a melting robot can be used to repair electronics or to remove something from the body.
A small shape-shifting robot can liquefy itself and assume a different form. Robot researchers describe this in the scientific journal matter.
The melting trick enables the robot to perform tasks in hard-to-reach places. For example, it can be used as a soldering machine, or as a tool to remove swallowed objects. He can also escape from cages.
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Robots already exist that are soft and flexible enough to work in narrow, vulnerable spaces, such as cavities in the human body. But they can’t get any stronger, which would make sense if they come under pressure or if they have to carry something heavy.
Liquid and solid
Robot researcher Carmel Majidi of Carnegie Mellon University in Pennsylvania and his colleagues have built a robot that can not only change shape, but also become stronger or weaker by becoming liquid and solid on command. They made their millimeter-sized robot from a mixture of the liquid metal gallium and microscopic pieces of a magnetic material of neodymium, iron and boron. In solid form, the material is strong enough to support an object thirty times its own mass.
To soften, stretch, move or melt the material into a crawling puddle, the researchers held it close to magnets. The custom-made magnetic fields then exerted forces on the magnetic bits inside the robot, distorting the metal as desired.
Electric currents
For example, the team was able to stretch the robot with the help of a magnetic field that pulled the grains in different directions. The researchers used a stronger field to pull the particles up, causing the robot to jump. And when Majidi and colleagues applied an alternating magnetic field, electrons in the liquid metal formed electric currents. This caused the robot to melt. “No other material I know of is as good at changing stiffness,” says Majidi.
Taking advantage of this flexibility, the team had two robots carry a small light bulb and solder it onto a printed circuit board. When they reached their destination, the robots melted to bond the bulb to the circuit board. The electricity could then run through the liquid metal, lighting the light bulb.
In an experiment with an artificial stomach, the researchers applied a different set of magnetic fields to direct the robot toward an object. Once there, the robot melted over the object, then dragged it out.
Lego doll
The researchers then gave their robot the shape of a Lego figure. They made the doll escape from a cage by liquefying it and letting it flow through the bars. Then they dripped the molten robot into a mold, so that it solidified back into its original puppet shape.
The fused robots could be used in situations where human or traditional robotic hands are impractical, robot researcher says LiZhang from the Chinese University of Hong Kong. For example, a liquid robot could replace a lost propeller in a spacecraft by flowing and solidifying in the right place, he says.
It is still too early to use them in live stomachs. Before that can be done, researchers must first develop methods to accurately track the robot’s position to ensure patient safety, Zhang said.