Researchers from Carnegie Mellon University (CMU) in Pennsylvania have developed a miniature robot that can transform and take a liquid form, which allows it to perform tasks in hard-to-reach places. In the future, it can be used as an automatic soldering machine or a tool for extracting swallowed objects from the stomach.
Robots that are soft and malleable enough to work in narrow spaces already exist, but they cannot make themselves more durable and strong under external influence or when they have to carry something heavier than themselves. Carmel Majidi from CMU and his colleagues have created a robot that can not only change shape, but also alternately take on a liquid or solid form.
They created a millimeter-sized robot from a mixture of gallium (Ga) and ferromagnetic neodymium-iron-boron (NdFeB) microparticles. In the solid state, the material was strong enough to withstand an object whose mass was 30 times its own. To make it soften, stretch, move or turn into a crawling puddle, depending on the tasks, the researchers placed it next to magnets. The tuned magnetic fields affected the tiny magnetic elements of the robot, moving them and deforming the metal in different directions.
For example, the team stretched the robot by applying a magnetic field that pulled these pellets in different directions. The researchers also used a stronger field to pull the particles up, forcing the robot to jump. When Majidi and his colleagues used an alternating magnetic field, electrons in the liquid metal of the robot formed electric currents. The passage of currents through the robot's body heated it and eventually caused it to melt.
"No other material I know is capable of changing its rigidity so much," says Majidi.
Using this flexibility, the team used two robots to transfer and solder a small light bulb to a printed circuit board. In another experiment, inside an artificial stomach, the researchers applied a different set of magnetic fields to force the robot to approach the object and pull it out. Finally, they shaped the robot into a Lego figure, and then helped it get out of the cage by melting it and forcing it to flow out between the bars. As soon as the puddle flowed out, the robot regained its original, solid form.
According to Li Zhang of the Chinese University of Hong Kong, these molten robots can be used for emergency repairs in situations where human or robotic hands become impractical. For example, a liquefied robot could replace a lost propeller on a spaceship by pouring into its place and then solidifying, he says. However, in order to use them inside a human stomach, researchers must first develop methods to accurately track the robot's position at each stage of the procedure to ensure patient safety.
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