The T-1000 in Terminator 2 could change shape at will, morph its hands into blades or turn parts of its body into a fluid to move through metal bars. “I saw this movie when I was a child—it was like, ‘Wow, can you imagine,’ I thought, ‘being able to do this?’” says Otger Campàs, a professor at Max Planck Institute of Molecular Biology and Genetics in Dresden, Germany. “Now I work on embryos. And what we saw in The Terminator actually happens in an embryo. This kind of shape shifting is what an embryo does.”
Campàs and his team drew inspiration from processes called fluidization and convergent extension—mechanisms that cells in embryos use to coordinate their behavior when forming tissues and organs in a developing organism. The team built a robotic collective where each robotic unit behaved like an embryonic cell. As a collective, the robots behaved like a material that could change shape and switch between solid and liquid states, just like the T-1000.
Real-world and sci-fi alloys
The T-1000 was a marvel to behold, but the movie gave no clues as to how it worked. This is why Campàs and his colleagues looked for clues elsewhere. Similar shape-shifting properties have been observed in embryos when you watch their development sped up using time-lapse imaging. “Tissues in embryos can switch between solid and fluid states to shape the organs. We were thinking how we could engineer robots that would do the same,” Campàs says.
The team focused on three abilities that enable cells in embryonic tissues to work their magic. The first is that they can move relative to each other even when they are tightly packed and connected. The second is signaling: releasing molecules that neighboring cells recognize and respond to, potentially by orienting their movement in a specific direction. The third is the ability of cells to adhere to one another, forming a strong and cohesive whole.
Campàs and his colleagues decided to design cell-like robots that could do all those things.
T-1000 building blocks
Each robot had motorized gears around its perimeter that could interlock with gears on other robots. The gears allowed the robots to move within the collective without breaking their bonds with each other, just like cells do in a living organism.
Linking the robots was a job of magnets that could rotate to maintain adhesion regardless of their orientation. Each robot also had a photodetector that could sense the polarity of light, allowing basic commands to be sent using a simple flashlight with a polarization filter. “The switch between solid and liquid states was driven by fluctuations of the force the motors applied, and we encoded the intensity of those fluctuations in the intensity of light,” says Matthew Devlin, a researcher at the Department of Mechanical Engineering at the University of California Santa Barbara and lead author of the study.
In response to light signals, two robotic collectives, 20 robots total, could elongate toward each other, touch in the middle, and form a bridge that could hold a load of just under 5 kilograms. After forming a cube, they could support an adult human weighing around 70 kilograms. They could also flow around an object, assume a complementary shape, and stiffen up to act as a wrench. “This was the Terminator idea of shapeshifting. This was exactly what we had in mind,” Campàs claims.
The only problem was, the robots were a bit above 5 centimeters in diameter. To get robotic collectives closer to Terminator’s mimetic polyalloy, the team wants to make the robots smaller. Much smaller.
Terminator nanobots?
“The good news is, you don’t have to go down with scale to what you see in living systems,” Campàs says. “Cells are roughly 10 microns. But anything around 100 microns—even up to 1 millimeter—robots would already be really impressive.” Unfortunately, we are rather far from making machines that small.
According to the team, robots working like ones they used in the study could be scaled down to 1 or 2 centimeters in diameter. “At this moment, it is impossible to make something the size of like a grain of rice with all the features we have, but it could well become possible within the next decade,” Campàs claims. But even if we do figure out the miniaturization part, there are other issues to solve, like powering all those robots up.
The robots used in the study were powered by lithium-ion batteries that could keep them operating continuously for about half an hour. But the power consumption was only significant during transitions from one shape to another. Once the collective was locked in a shape, they only needed tiny amounts of power. The big problem is that each robot has to be charged manually. This worked for a collective of 20 robots but would become a real issue if the number of robots went up to hundreds or thousands. One possible solution researchers see is wireless charging, provided we could make it work over longer distances. For now, though, the shape-shifting robotic collective was meant primarily as a proof-of-concept.
“We’re far from the Terminator thing, let me be clear about that. It’s not that we’re doing it tomorrow. If you talk to people doing micro mechanical devices, you’ll know it’s not easy,” Campàs says. But he said the research community now has an example of how something like the T-1000 material could work, and miniaturizing robots is all that’s left to do. “Our goal was to get people excited to actually go and do it,” Campàs adds.
Science, 2025. DOI: 10.1126/science.ads7942