Scientists have made a breakthrough in robotics: a shapeshifting robot that can switch between liquid and metal states to navigate tricky environments without compromising on 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 made the robots navigate obstacle courses, remove or deliver objects to a model of the human stomach, and even liquefy to escape a cage before reforming back into its original humanoid shape.
“Giving robots the ability to switch between liquid and solid states endows them with more functionality,” says engineer Chengfeng Pan of The Chinese University of Hong Kong in China.
There are many potential uses for small robots that can get around places too small or convoluted for humans to manage with typical tools, from finicky 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 more difficult 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 alter the stiffness of their tissues to improve load capacity and limit physical damage, while octopuses can alter the rigidity of their arms for camouflage, object manipulation, and locomotion.
To design a robot that can do something similar, the researchers needed a non-toxic material that can easily shift between soft and rigid states in ambient temperature. They turned to 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 transitional 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 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.”
After testing to see whether the transition from solid to liquid was reversible (it was), the researchers ran their little robots through a gamut of tests. The robots could leap over small moats, climb over obstacles, and even split up to perform cooperative tasks moving objects around before recombining and resolidifying.
