Xenobots: The Living Programmable Organisms Representing New Class of Artifact

A team of scientists from the University of Vermont has re-purposed living cells—scraped from frog embryos—and assembled them into entirely new life-forms – xenobots. These millimeter-wide bots can move toward a target, perhaps pick up a payload (like medicine that needs to be carried to a specific place inside a patient)—and heal themselves after being cut.

According to Joshua Bongard, a computer scientist and robotics expert at the University of Vermont who co-led the new research, "these are novel living machines. Xenobots are neither a traditional robot nor a known species of animal. It's a new class of artifact: a living, programmable organism."

Reportedly, the new xenobots were designed on a supercomputer at UVM—and then assembled and tested by biologists at Tufts University. The co-leader Michael Levin who directs the Center for Regenerative and Developmental Biology at Tufts said, "we can imagine many useful applications of these living robots that other machines can't do – like searching out nasty compounds or radioactive contamination, gathering microplastic in the oceans, traveling in arteries to scrape out plaque."

The new research results were published on January 13 in the Proceedings of the National Academy of Sciences.

This research, for the first time ever, "designs completely biological machines from the ground up," the team writes in their new study.

According to UVM Today, with months of processing time on the Deep Green supercomputer cluster at UVM's Vermont Advanced Computing Core, the team—including lead author and doctoral student Sam Kriegman—used an evolutionary algorithm to create thousands of candidate designs for the new life-forms. Attempting to achieve a task assigned by the scientists—like locomotion in one direction—the computer would, over and over, reassemble a few hundred simulated cells into myriad forms and body shapes. As the programs ran—driven by basic rules about the biophysics of what single frog skin and cardiac cells can do—the more successful simulated organisms were kept and refined, while failed designs were tossed out. After a hundred independent runs of the algorithm, the most promising designs were selected for testing.

Post selection, the team at Tufts, led by Levin and with key work by microsurgeon Douglas Blackiston—transferred the in silico designs into life. First, they gathered stem cells, harvested from the embryos of African frogs, the species Xenopus laevis (hence the name "xenobots"). These were separated into single cells and left to incubate. Then, using tiny forceps and an even tinier electrode, the cells were cut and joined under a microscope into a close approximation of the designs specified by the computer, notes UVM Today.

Assembled into body forms never seen in nature, the xenobots cells began to work together. The skin cells formed a more passive architecture, while the once-random contractions of heart muscle cells were put to work creating ordered forward motion as guided by the computer's design, and aided by spontaneous self-organizing patterns—allowing the robots to move on their own.

According to Levin, "if humanity is going to survive into the future, we need to better understand how complex properties, somehow, emerge from simple rules." Much of science is focused on controlling the low-level rules. He says, "we also need to understand the high-level rules. If you wanted an anthill with two chimneys instead of one, how do you modify the ants? We'd have no idea."

Further, he adds, "I think it's an absolute necessity for society going forward to get a better handle on systems where the outcome is very complex. A first step towards doing that is to explore: how do living systems decide what an overall behavior should be and how do we manipulate the pieces to get the behaviors we want?"

According to him, in other words, "this study of xenobots is a direct contribution to getting a handle on what people are afraid of, which is unintended consequences – whether in the rapid arrival of self-driving cars, changing gene drives to wipe out whole lineages of viruses, or the many other complex and autonomous systems that will increasingly shape the human experience."

UVM's Josh Bongard says, "there's all of this innate creativity in life. We want to understand that more deeply—and how we can direct and push it toward new forms."