Hasta La Vista, Static Robots

For pipe inspections, a pill-shaped robot with a continuous track might be the best choice. Package deliveries, on the other hand, could be made much more quickly with an unmanned aerial vehicle capable of lifting a heavy payload. When a task spans a wide variety of terrain types, from sand to loose gravel and rolling hills, a quadrupedal robot would offer the versatility that is needed for getting around. For each application, selecting an appropriate robot is as easy as matching up the requirements with its skills.

Easy enough, right? Well, yes… but this is also an incredibly inefficient approach where many different tasks need to be handled by robots. If we only had more versatile robots that could adapt to different situations, things would be so much easier. If, for instance, the T-1000 robot from the movie Terminator 2 (minus the evil assassin programming) were a real thing, a single robot could transform to tackle any conceivable job. For those that need a refresher, the T-1000 was made of a liquid metal that could shapeshift at will to change its appearance or capabilities.

Of course the mimetic polyalloy imagined in the movies is nothing more than a fantasy, so we still have to customize robots for specific use cases. But lack of this fictional material did not stop researchers at the University of California, Santa Barbara from attempting to make their own shape-shifting robot from technologies that actually exist in the real world. No, it is nowhere near the level of cool that is flowing liquid metal, but the swarm of interlocking robots in their design can shapeshift in some interesting ways all the same.

Inspired by how cells in a developing embryo change their shape to form organs and tissues, the researchers designed a collective of small robots that can transition between solid and fluid-like states. They built a system where each robot moves while maintaining its connections with its neighbors, similar to how embryonic cells behave when morphing into different structures.

The robots achieve this fluidity through three key principles: movement, signaling, and adhesion. Each unit features motorized gears that interlock with others, allowing them to shift within the collective without losing cohesion. The robots also communicate through light signals, responding to instructions that direct their movement. Additionally, rotating magnets help them maintain adhesion, ensuring that they stay connected regardless of their orientation.

By controlling the forces exerted by the robots’ motors, the researchers could adjust the material properties of the entire collective. In one mode, the robots behaved like a solid, forming stable structures such as a cube that could support a human’s weight. In another, they acted like a fluid, easily stretching into new shapes.

Despite these achievements, the technology still faces some challenges. Currently, each robot measures about five centimeters in diameter — much too large for many applications. For this system to really flow like liquid metal, each robot would need to be about 50 times smaller, at a minimum. Present technologies cannot achieve that goal. Looking ahead, the team hopes that nanobots of this sort will be feasible to construct in the years ahead. However, miniaturization is not the only hurdle they need to clear. The robots currently rely on lithium-ion batteries with limited operation time, and each unit must be manually recharged. Wireless charging solutions may eventually solve this issue, but they, too, require further development.

If future developments overcome the hurdles of size and power, we might one day see robots that can change form as easily as cells in an embryo — bringing us closer to the versatile, shape-shifting machines of science fiction.