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The researchers created their magnetoactive solid-liquid phase transitional machine material by embedding magnetic particles into gallium, a metal with a low melting point of 85.64 °F (29.8 °C).

"The magnetic particles here have two roles," explained senior author and mechanical engineer Carmel Majidi from Carnegie Mellon University.

"One is that they make the material responsive to an alternating magnetic field, so you can, through induction, heat up the material and cause the phase change. But the magnetic particles also give the robots mobility and the ability to move in response to the magnetic field."

The new material, therefore, doesn't rely on heat guns, electrical currents, or any other external heat sources to change states. This sets it apart from existing phase-shifting materials that are typically used for similar applications. According to the researchers, the new material's liquid phase is also much less viscous than other phase-changing materials and much better resembles a liquid state.

Novel material could solve "specific medical and engineering problems"

The team put their material through its paces in an obstacle course. They guided it using a magnetic field and made it jump over moats, climb walls, and even split in two to move separate objects before joining back together.

In an impressive video, the material, crafted into a humanoid shape, liquefies and moves through a grid before molding itself back together on the other side. "Now, we're pushing this material system in more practical ways to solve some very specific medical and engineering problems," Pan explained.

The scientists believe their technology could ultimately be used to deliver medicine to patients in novel ways. One test, for example, saw them deliver drugs into a model stomach and also remove a foreign object from the same stomach. They also showed that the material could ooze into hard-to-reach broken circuits and repair them by acting as both a solder and a conductor. It could also liquefy, enter a screw socket, solidify, and serve as an easy-to-use screw.

"Future work should further explore how these robots could be used within a biomedical context," Majidi explained. "What we're showing are just one-off demonstrations, proofs of concept, but much more study will be required to delve into how this could actually be used for drug delivery or for removing foreign objects."

The researchers outlined their work in a new paper published in the journal Matter.