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Frog Cell ‘Xenobots’ Can Self-Assemble and Navigate Mazes

In early 2020, a team of computer scientists from the University of Vermont and biologists at Tufts University built “biological robots” for the first time. Now, a little more than a year later, the same team’s discovered a new way to build the so-called xenobots; one that involves much less direct physical manipulation. Which is a feature that makes the resultant bio-machines—which can self-assemble and navigate mazes—all the more astounding.

Quanta Magazine reported on the new iteration of the researchers’ xenobots, which the team outlined in a paper recently published in Science Robotics. For this experiment, the researchers, who’re aiming to not only explore the origins of multicellular life, but also build organic tools that could say, eat up plastic in the ocean, went for a more “bottom up” assembly approach as opposed to “top down.”

While the team crafted the first xenobot generation from frog cells, they produced this generation in a more natural fashion; by removing skin cells from frog embryos and leaving them to develop into autonomous clusters. Lo and behold, some cells in each cluster began to use their cilia—hair-like projections that can wave and rotate—as “legs;” allowing the respective, whole clusters to swim in aqueous solution as singular organisms.

“We are witnessing the remarkable plasticity of cellular collectives, which build a rudimentary new ‘body’ that is quite distinct from their default—in this case, a frog—despite having a completely normal genome,” Michael Levin, professor of biology at Tufts and corresponding author of the new study, said in a press release. “In a frog embryo, cells cooperate to create a tadpole. Here, removed from that context, we see that cells can re-purpose their genetically encoded hardware, like cilia, for new functions such as locomotion,” the biologist added.

The xenobots (a portmanteau of the frog species providing the cells, Xenopus laevis, and “robots”) themselves look like globular popcorn. In the video above, the researchers show how they made the xenobots, and how they move. And indeed, they seem like little, mindless robots. A lot like something you’d see in an automated warehouse. The bots can even assemble “communities” and exchange environmental information with chemical signals.

Researchers have created biological robots, dubbed xenobots, out of frog cells, and they're able to self-assemble and navigate mazes.

Douglas Blackiston / Tufts University

Its amazing cells “can spontaneously take on new roles…without long periods of evolutionary selection for those features,” Levin added. In fact, the researchers are astounded that the xenobots assemble at all; namely because their new designs are not “programmed” into their frog genome.

Looking forward, the team’s investigating ways to make xenobot “swarms” for applications in biomedicine and environmental preservation. Which, while amazing (and also very creepy,) is almost secondary to watching xenobots build themselves thanks to a kind of natural “collective cellular map” rather than programmed genomic instruction. A phenomenon that really makes you wonder about The Force (of life).

Biological robots called xenobots are in a large, glowing cluster together on a black background.

Douglas Blackiston / Tufts University

Feature image: Douglas Blackiston / Tufts University