The shape of mobile liquid metal robots is not limited to science fiction anymore.
Small machines can switch from solid to liquid and back again to squeeze into tight spaces and accomplish tasks like soldering a circuit board, researchers report on January 25. Material.
This property of alternating phase, which can be remotely controlled with a magnetic field, is gallium metal. Researchers immersed the metal with magnetic particles to direct the movement of the metal magnets. This new material could help scientists create soft, flexible robots that can glide through narrow passages and be guided externally.
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Scientists have developed magnetically controlled soft robots for years. The most existing materials for these robots are made of materials that are either stretched, but solid, that cannot pass through the narrowest of spaces, or magnetic liquids, that are fluid, but cannot carry heavy loads.SN: 7/18/19).
In the new study, researchers will combine both approaches after finding inspiration from nature.SN: 3/3/21). Sea cucumbers, for example, “can change their stiffness very quickly and reversibly,” says mechanical engineer Carmel Majidi of Carnegie Mellon University in Pittsburgh. “The challenge for us is for engineers to imitate that in soft materials systems.”
The team then turned to gallium, melting the metal at about 30° Celsius – slightly above room temperature. Rather than connecting a heater to a piece of metal to change its state, the researchers exposed it to a rapidly changing magnetic field to melt it. The alternating magnetic field generates electricity inside the coil, causing it to heat up and melt. The material solidifies when left to cool to room temperature.
When the magnetic particles are scattered through the gallium, the permanent magnet can pull around. A magnet can move matter in solid form at a speed of about 1.5 meters per second. The upgraded Gaul can also carry around 10,000 times its weight.
External magnets can still manipulate the liquid form, causing it to split and confuse. But controlling the motion of the fluid is more difficult because the particles in the gallium can rotate freely and have magnetic poles that are not aligned out of the melt. Because of their different orientations in the magnet, the particles move in different directions.
Majidi and colleagues tested their design on small machines that performed different tasks. In a demonstration straight from the movie Terminator 2slipping through the bars of a toy prison cell and solidifying it into its original form using a mold placed next to the enclosure.
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On the more practical side, one small machine removed the ball from a model of a human stomach, melting it slightly so that the foreign object would wrap itself before leaving the organ. But gallium would yield by itself inside the real human body, since the metal is liquid at body temperature, around 37° C. Some more metals, such as bismuth and tin, are added to gallium in biomedical applications. The authors say that the material is beginning to lift. In another demonstration, material was melted and hardened to solidify a circuit board.
Although this phase-sufficient material is a big step in the field, questions remain about its biomedical applications, says biomedical engineer Amir Jafari of the University of North Texas in Denton, who was not involved in the work. One big challenge, he says, is precisely controlling the magnetic force inside the human body generated by an external device.
“It’s a compelling tool,” says robotics engineer Nicholas Bira of Harvard University, who was also not involved in the study. But, he adds, scientists who study soft robotics are constantly creating new materials.
“The real innovation is going to be in the combination of these different new materials.”
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