Xenobot 3.0: a self-replicating living robot - hero image

Scientists build self-replicating living robots

Image credit: Douglas Blackiston and Sam Kriegman

US researchers have discovered a new form of biological reproduction and have created what they say are the world’s first living robots that can self-replicate.

The robots are the brainchild of a collaborative team at the University of Vermont, Tufts University and the Wyss Institute for Biologically Inspired Engineering at Harvard University, the same team that built the first living robots: 'Xenobots' - assembled from frog cells – reported in 2020.

According to the researchers, these computer-designed and hand-assembled organisms can swim out into their tiny dish, find single cells, gather hundreds of them together, and assemble 'baby' Xenobots inside their Pac-Man-shaped “mouth”.

A few days later, these babies become new Xenobots that look and move just like themselves. And then these new Xenobots can go out, find cells, and build copies of themselves, and this process repeats.

“With the right design – they will spontaneously self-replicate,” said Joshua Bongard, a computer scientist and robotics expert at the University of Vermont who co-led the new research.

In a Xenopus laevis frog, these embryonic cells would develop into skin. “They would sit on the outside of a tadpole, keeping out pathogens and redistributing mucus,” said Michael Levin, a professor of biology and director of the Allen Discovery Center at Tufts. “But we’re putting them into a novel context. We’re giving them a chance to reimagine their multicellularity.”

According to Douglas Blackiston, the senior scientist at Tufts University who assembled the Xenobot 'parents' and developed the biological portion of the new study, people have thought for quite a long time that we [researchers] have worked out all how life can reproduce or replicate. “But this is something that’s never been observed before.”

An AI-designed, Pac-Man-shaped “parent” organism (in red) beside stem cells that have been compressed into a ball—the “offspring” (green) - inline image

An AI-designed, Pac-Man-shaped “parent” organism (in red) beside stem cells that have been compressed into a ball – the “offspring” (green).

Image credit: Douglas Blackiston and Sam Kriegman

In earlier experiments, the scientists found the Xenobots could achieve simple tasks. But now they find these biological objects – a computer-designed collection of cells – will spontaneously replicate. “We have the full, unaltered frog genome,” Levin explained, “but it gave no hint that these cells can work together on this new task,” of gathering and then compressing separated cells into working self-copies.

On its own, the Xenobot parent, made of some 3,000 cells, forms a sphere. “These can make children, but then the system normally dies out after that. It’s very hard to get the system to keep reproducing,” said Sam Kriegman, a post-doctoral researcher at Tuft’s Allen Center and Harvard University’s Wyss Institute for Biologically Inspired Engineering.

With the help of an artificial intelligence program working on the Deep Green supercomputer cluster at UVM’s Vermont Advanced Computing Core, however, an algorithm could test billions of body shapes in simulation – triangles, squares, pyramids, starfish – to find ones that allowed the cells to be more effective at the motion-based 'kinematic' replication reported in the new research.

“We asked the supercomputer at UVM to figure out how to adjust the shape of the initial parents, and the AI came up with some strange designs after months of chugging away, including one that resembled Pac-Man,” said Kriegman. “It’s very non-intuitive. It looks very simple, but it’s not something a human engineer would come up with. Why one tiny mouth? Why not five?”

Kriegman sent the results to Blackiston, and he built the Pac-Man-shaped parent Xenobots. “Then those parents built children, who built grandchildren, who built great-grandchildren, who built great-great-grandchildren,” he added.

The team sees promise in the research or advancements toward regenerative medicine. “If we knew how to tell collections of cells to do what we wanted them to do, ultimately... solves traumatic injury, birth defects, cancer, and ageing,” said Levin. “ These different problems are here because we don’t know how to predict and control what groups of cells are going to build. Xenobots are a new platform for teaching us.”


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