From Solid to Liquid: A Gallium Robot as a Shape Shifter

by | 26. Jan 2023 - 14:19 | Technologies

Numerous applications in medicine and mechanical engineering are conceivable.

It sounds like science fiction: a robot that can switch between solid and liquid form. An international team of researchers has built one in miniature and presented it in the scientific journal Matter. The study impressively demonstrates the robot’s capabilities on the basis of videos: It was able to escape from a narrow cage by becoming liquid and then reassemble itself in a small mold. Likewise, it was able to jump over trenches, climb up walls and even split in half briefly to avoid an object.

This is made possible by a new material that can change its state under the influence of a magnetic field. To do this, the scientists embedded magnetic neodymium-iron-boron microparticles in gallium, a technology metal that liquefies at just below 30 degrees due to its low melting point.

The robot shortly before “breaking out” of its prison. Image from the video of the scientists. Click on the image to see the video

Credit: Wang and Pan et al.

Shape change gives robots more functionality

This brings together two trends that can currently be observed in the booming research field of robotics: Solid robots, which are not very flexible, and their “soft” counterparts. The latter are much more adaptable, but weak and difficult to control, according to Eurekalert. Instead of combining hard and soft components, the research team focused on developing a so-called phase-shifting material. The goal is to give robots more functionality, explains study leader Chengfeng Pan, an engineer at the Chinese University of Hong Kong.

The magnetic particles perform two tasks, according to author Carmel Majidi of Carnegie Mellon University (USA): They make gallium receptive to an alternating magnetic field. This allows the metal to be heated to between 25 and 35 °C by induction to bring about the phase change. They also give the robot mobility and the ability to move in response to the magnetic field. Thus, unlike phase-shifting materials manufactured in the past, no external heat sources such as heat guns or electric currents are needed to trigger the transformation from solid to liquid, he said.

Solving medical and technical problems

In practice, this could help solve specific medical and technical problems, Pan says. Tests have shown that the robot can remove foreign objects from a model stomach, as well as administer drugs to it, he says. It could also be used in assembly and repair, for example as an intelligent soldering machine and universal screw to assemble parts in hard-to-reach places. The wide range of possible applications will now be explored in further studies.

Photo: iStock/Igor Krasilov

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