Xenobots, configured from hundreds of cells, can self-repair, break into pieces, and even work together to build large complex structures. Credit: PNAS.

  • Innovation

The first robots created with stem cells

Xenobots are already a reality, in tiny biological machines made from the cells of a frog. Their plasticity and their ability to repair themselves make them promising tools for creating organs or even erecting buildings. They can also help us answer one of the great questions in science: What is life?


They are neither traditional robots nor organisms with a life of their own. Xenobots fall somewhere in the middle, being the first machines created from living cells. They also stand out because they can be programmed for different tasks. At the moment, they are capable of carrying out basic actions such as swimming or transporting small particles, but their creators, four researchers from the USA, are looking to much more ambitious applications in the future in fields such as medicine, robotics or construction.

How does a xenobot differ from a traditional robot? First of all, in size. Michael Levin, a biologist at Tufts University and one of the creators of these living machines, explains that xenobots are much smaller. They are made up of hundreds of cells, measure about half a millimetre, have no reproductive organs and live for about seven days. After that, the researchers explain, they degrade and stop working. In addition, despite their small size, they can divide into pieces and become even smaller, or work together like a swarm. As Levin says: "They are not made of dumb parts, like most robots; they have a degree of flexible behaviour that comes from the intelligence of their cells."

To create the xenobots, different stem cells were removed from a frog and assembled into new configurations created through algorithms, creating these living robots. Credit: Smithsonian.

Programmable synthetic organisms

To create these biobots, the scientists harvested stem cells from fertilized frog embryos to use as raw material. Specifically, they used two types of stem cells —skin and heart muscle— taken from the African clawed frog (Xenopus laevis), from which the robots have inherited their name. Then, with a supercomputer, they simulated thousands of random configurations of the cells and analysed their possible behaviours. After months of work and complicated calculations to assign complex tasks to these synthetic organisms, they built the best designs, combining different biological tissues, as they explain in the specialised magazine PNAS. The result brings robotics one step closer to achieving one of its great aspirations, the creation of machines from living components to which human behaviours are applied.

In fact, xenobots can perform microscopic tasks that traditional robots are currently unable to do. Although these functions are still limited, researchers suggest that they will significantly revolutionise many sectors. At the moment they can travel in one direction, move about under water, point at each other, transport small particles by pushing them, repair themselves when they are damaged and create different shapes. In the future, as Levin points out, they could be put to use in the environment to identify or scoop up toxins or certain chemicals. In the human body, they could be used to "hunt for cancer cells or to remodel arthritic joints," the researcher also notes. They could even work together to build large complex living structures such as organs for transplant; or non-living ones such as buildings. The biologist says, for example, that xenobots could build underwater habitats made of biological and inorganic components.

Programmable to carry out almost any task, the plastic capacity of these living robots opens up possibilities for achieving sustainable buildings. Credit: PNAS.

Indestructible live automata

Exploring the plasticity of these living machines could open up possibilities currently unimaginable in the construction sector, especially given their ability to work together and their indestructible nature that allows them to heal themselves after being damaged. It is still too early to know what kind of structures they will eventually be able to build, how long it will take them to do so, whether they will assist humans or work independently, and what process they will follow.

But researchers do agree that xenobots have emerged as an alternative for achieving sustainable buildings. They could, in fact, help curb the CO2 emissions generated by the construction sector. "Because xenobots are machines made entirely of living cells, they could someday help us achieve carbon-neutral or even carbon-negative construction like plants do," says Sam Kriegman, a robotics expert at the University of Vermont and co-author of the research.

All these ideas are still hypotheses for the moment, so we may have to wait a long time to see if they are finally realised. What is certain is that these first living machines have reminded us of numerous unanswered questions in biology: How do cells cooperate to build complex, functional bodies? How do they know what to build? What signals do they exchange to do so? Finding the answers will shed light on such fundamental topics as the origin of multicellularity or the evolution of cells. But they will also open the way for progress in the development of these xenobots and their capabilities, beyond those that are currently envisioned.

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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.

  • Tungsteno
  • Robots
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  • Xenobots

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