Scientists create shape-shifting humanoid robot that can float and reform: ScienceAlert

Scientists have made a breakthrough in robotics: a shape-shifting robot that can switch between liquid and metal states to navigate difficult environments without compromising strength.

Because they can be both soft and hard, the small, sea cucumber-inspired robots can overcome the limitations of robots that are only one or the other, and thus have the potential to provide greater utility in areas such as electronics assembly and even medical applications.

Researchers had the robots navigate obstacle courses, remove or deliver objects to a model of the human stomach, and even float to escape a cage before returning to its original humanoid form.

“Giving robots the ability to switch between liquid and solid states gives them more functionality,” says engineer Chengfeng Pan from The Chinese University of Hong Kong in China.

Timelapse showing the robot’s daring prison escape. (Wang et al., Fabric2023)

There are many potential uses for tiny robots that can get around places that are too small or intricate for humans to handle with typical tools, from delicate repair work to targeted drug delivery. But hard materials aren’t the best for navigating confined spaces or tight angles, while soft, more flexible robots tend to be weak and harder to control.

To find a compromise, a team of researchers led by Pan and his colleague, Qingyuan Wang of Sun Yat-sen University in China, turned to nature as a source of inspiration. Animals such as sea cucumbers can change the stiffness of their tissues to improve load capacity and limit physical damage, while octopuses can change the stiffness of their arms for camouflage, object manipulation and locomotion.

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To design a robot that can do something similar, the researchers needed a non-toxic material that can easily switch between soft and rigid states at ambient temperature. They turned into gallium, a soft metal that has a melting point of 29.76 degrees Celsius (85.57 degrees Fahrenheit) at standard pressure—just a few degrees below the average human body temperature. You can melt gallium just by holding it in your hand.

The researchers embedded a gallium matrix with magnetic particles, creating what they call a “magnetoactive solid-liquid phase transition machine”.

“The magnetic particles here have two roles,” says mechanical engineer Carmel Majidi of Carnegie Mellon University, one of the senior authors on the team’s paper.

“One is that they make the material react to an alternating magnetic field, so that through induction you can 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.”

After testing to see if the transition from solid to liquid was reversible (it was), the researchers ran their tiny robots through a series of tests. The robots could jump over small moats, climb over obstacles, and even split up to perform cooperative tasks of moving objects around before recombining and solidifying again.

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They even had a small humanoid version – shaped like a Lego figure – melted to escape a small prison cell, seep through the bars and transform on the other side in homage to a scene from the movie Terminator 2.

The team then investigated practical applications. They created a model of a human stomach and had the robot swallow and remove a small object contained within it—a useful way, one imagines, of extracting swallowed batteries, for example—and then perform the reverse operation and deliver an object the way. the team hopes it can deliver drugs.

For circuit repair, the robots could navigate to and melt onto circuits to act as a conductor and solder; and even act as a fastener that seeps into threaded screws and solidifies, performing the function of a screw without anyone needing to secure it in place.

For real-world applications, the phase transition machine would need some adjustments. For example, because the human body is higher than the melting point of pure gallium, a robot designed for biomedical purposes could have a gallium-based alloy matrix that would raise the melting point while maintaining functionality.

That, the researchers say, has yet to be investigated in detail.

“Future work should further investigate how these robots can be used in a biomedical context,” says Majidi.

“What we’re showing is just one-off demonstrations, proofs of concept, but a lot more study will be required to delve into how this could actually be used for drug delivery or to remove foreign bodies.”

The research is published in Fabric.

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