Scientists Just Created Shape-Shifting Robots That Flow Like Liquid and Harden Like Steel

Researchers have designed a robotic material that transforms like a living organism.

Inspired by embryos, these disk-shaped robots use magnets, motors, and light to shift between rigid and fluid states. The result? A self-healing, shape-shifting system that could change how we build and interact with materials.

Robots That Behave Like Materials

“We’ve figured out a way for robots to behave more like a material,” said Matthew Devlin, a former doctoral researcher in the lab of UCSB mechanical engineering professor Elliot Hawkes, and the lead author of a study published in the journal Science on February 20. Composed of individual, disk-shaped autonomous robots that look like small hockey pucks, the members of the collective are programmed to assemble themselves together into various forms with different material strengths.

One of the biggest challenges the team tackled was creating a robotic material that could be both stiff and strong while also able to flow into new configurations. “Robotic materials should be able to take a shape and hold it” Hawkes explained, “but also able to selectively flow themselves into a new shape.” In the past, robots tightly connected in a collective couldn’t easily rearrange themselves. Now, that has changed.

Taking Inspiration from Embryos

For inspiration, the researchers looked to how embryos form in nature, drawing on the work of Otger Campàs, former UCSB professor and now director of PoL at the Dresden University of Technology. “Living embryonic tissues are the ultimate smart materials,” Campàs said. “They have the ability to self-shape, self-heal, and even control their material strength in space and time.” His lab previously discovered that embryos can temporarily soften — almost like melting glass — to sculpt their final forms. “To sculpt an embryo, cells in tissues can switch between fluid and solid states; a phenomenon known as rigidity transitions in physics,” he added.

During the development of an embryo, cells have the remarkable ability of arranging themselves around each other, turning the organism from a blob of undifferentiated cells into a collection of discrete forms — like hands and feet — and of various consistencies, like bones and brain. The researchers concentrated on enabling three biological processes behind these rigidity transitions: the active forces developing cells apply to one another that allow them to move around; the biochemical signaling that allow these cells to coordinate their movements in space and time; and their ability to adhere to each other, which ultimately lends the stiffness of the organism’s final form.

Magnets and Motors: The Key to Shape-Shifting

In the world of robots, the equivalent of cell-cell adhesion is achieved with magnets, which are incorporated into the perimeter of the robotic units. These allow the robots to hold onto to each other, and the entire group to behave as a rigid material. Additional forces between cells are encoded into tangential forces between robotic units, enabled by eight motorized gears along each robot’s circular exterior. By modulating these forces between robots, the research team was able to enable reconfigurations in otherwise completely locked and rigid collectives, allowing them to reshape. The introduction of dynamic inter-unit forces overcame the challenge of turning rigid robotic collectives into malleable robotic materials, mirroring living embryonic tissues.

The biochemical signaling, meanwhile, is akin to a global coordinate system. “Each cell “knows” its head and tail, so then it knows which way to squeeze and apply forces,” Hawkes explained. In this way, the collective of cells manages to change the shape of the tissue, such as when they line up next to each other and elongate the body. In the robots, this feat is accomplished by light sensors on the top of each robot, with polarized filters. When light is shone on these sensors, the polarization of the light tells them in which direction to spin their gears and thus how to change shape. “You can just tell them all at once under a constant light field which direction you want them to go, and they can all line up and do whatever they need to do,” Devlin added.

A Smart Material That Adapts and Heals

With all this in mind, the researchers were able to tune and control the group of robots to act like a smart material: sections of the group would turn on dynamic forces between robots and fluidize the collective, while in other sections the robots would simply hold to each other create a rigid material. Modulating these behaviors across the group of robots over time allowed the researchers to create robotic materials that support heavy loads but can also reshape, manipulate objects, and even self-heal.

Currently, the proof-of-concept robotic group comprises a small set of relatively large units (20). However, simulations conducted by former postdoctoral fellow Sangwoo Kim in the Campàs laboratory, and now assistant professor at EPFL, indicate the system can be scaled to larger numbers of miniaturized units. This could enable the development of robotic materials comprising of thousands of units, that can take on myriad shapes and tune their physical characteristics at will, changing the concept of objects that we have today.

From Sci-Fi to Reality

In addition to applications beyond robotics, such as the study of active matter in physics or collective behavior in biology, the combination of these robotic ensembles with machine learning strategies to control them could yield remarkable capabilities in robotic materials, bringing a science fiction dream to reality.

Reference: “Material-like robotic collectives with spatiotemporal control of strength and shape” by Matthew R. Devlin, Sangwoo Kim, Otger Campàs and Elliot W. Hawkes, 20 February 2025, Science.
DOI: 10.1126/science.ads7942

This study was supported by the National Science Foundation (NSF; grant 1925373) in the United States of America, and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy–EXC 2068–390729961 – Cluster of Excellence Physics of Life of TU Dresden

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