The millimeter-wide computer-designed "xenobots" - made of cells scraped from frog embryos - can move toward a target, perhaps pick up and deliver a payload (such as a medicine), and heal themselves after being cut. These "living robots," say the researchers, promise advances in applications from in-patient intelligent drug delivery to toxic waste clean-up.
"These are novel living machines," says Joshua Bongard, a computer scientist and robotics expert at the University of Vermont who co-led the new research. "They're neither a traditional robot nor a known species of animal. It's a new class of artifact: a living, programmable organism."
The new creatures were designed using months of processing time on the Deep Green supercomputer cluster at UVM's Vermont Advanced Computing Core and then assembled and tested by biologists at Tufts University (Medford, MA).
Co-leader Michael Levin, who directs the Center for Regenerative and Developmental Biology at Tufts, says, "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 xenobots were developed using 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 supercomputer 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.
To transfer the "in silico" designs into life, the researchers first gathered stem cells, harvested from the embryos of African clawed frogs - i.e., species Xenopus laevis and hence the