The robot's transformation has been widely compared to a scene from Terminator. Chinese researchers behind the technology claim to have been inspired by sea cucumbers.
A 1991 film Terminator 2: Judgement Day sees T-1000, a shape-shifting android assassin, walk through metal bars, and a tiny real-life robot can now also do the same – well, almost.
Unlike the T-1000, the robot does not simply walk through the grid but rather changes its form from solid to liquid to slide through a gap between the bars that would otherwise be too narrow for it to pass.
While traditional robots are "hard-bodied and stiff," soft robots are flexible but weak and hard to control, researchers said.
"Giving robots the ability to switch between liquid and solid states endows them with more functionality," Chengfeng Pan, an engineer at the Chinese University of Hong Kong who led the study, said in a statement.
Researchers created the new shape-shifting material by embedding magnetic particles in gallium, a metal that melts at about 30°C (or about 86°F).
"The magnetic particles here have two roles," said Carmel Majidi, a senior study author and a mechanical engineer at Carnegie Mellon University in Canada. "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.”
Magnetic particles also make the robot move in response to a magnetic field. Using the magnetic field, researchers had the robot jump over the moat, climb a wall, and even split in half to move other objects in coordination before merging back – bringing it another step closer to the T-1000.
"Now, we're pushing this material system in more practical ways to solve some very specific medical and engineering problems," Pan said.
Potential applications include biomedical use, such as removing foreign objects from human bodies or delivering drugs on demand. The technology could also be used as a universal "screw" in hard-to-reach spaces.
Despite the analogies with the Terminator, researchers said they had drawn inspiration from marine animals like sea cucumbers that can alter the stiffness of their tissue when necessary.
Other animal-inspired research includes a spaghetti-like robotic gripper based on a jellyfish.
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