Using skin patches from frog embryo cells, scientists have grown creatures different from anything else on Earth, according to a new study. These microscopic “living machines” can swim, sweep debris, and heal after a blow.
Scientists often strive to understand the world as it exists, says Jacob Foster, a UCLA collective intelligence researcher who is not involved in this research. But the new study, published March 31 in Science Robotics, is part of a "liberating moment in the history of science," Foster says. "A reorientation towards the possible."
In a way, the bots were made by themselves. Scientists removed small clusters of stem cells from the skin of frog embryos to see what these cells would do on their own. Separated from their usual spots in a growing frog embryo, the cells organized into balls and grew. About three days later, the groups, called xenobots, began swimming.
Typically, similar structures called cilia in frog skin repel pathogens and spread mucus. But in the xenobots, the cilia allowed them to circulate around. That amazing development “is a great example of life reusing what’s on hand,” says study co-author Michael Levin, a biologist at Tufts University in Medford, Mass.
And that process happens fast. “This is not a type of effect where evolution has found a new use over hundreds of thousands of years,” Levin says. "This happens before your eyes within two or three days."
Xenobots have no nerve cells or brains. However, xenobots, each about half a millimeter wide, can swim through very thin tubes and traverse curved mazes. When placed in sand filled with small particles of iron oxide, xenobots can drag the garbage into piles. Xenobots can even heal; after being cut, the bots return the zipper in their spherical shapes.
Scientists continue to work on the basics of xenobot life. Creatures can live about 10 days without food. When fed on sugar, xenobots can live longer (although they do not continue to grow). “We cultured them for more than four months in the lab,” says study co-author Doug Blackiston, also at Tufts. “They do really interesting things if you cultivate them,” including forming strange shapes like a balloon.
It is not yet clear what kind of work these xenobots could do, if any. Researchers say in the head clean waterways, arteries or other small spaces. More generally, these organisms may have lessons on how bodies are built, Levin says.
With the advent of new organisms ethical issues arise, warns Kobi Leins, a digital ethics researcher at the University of Melbourne in Australia. “Scientists like to do things and they don’t necessarily think about what the repercussions are,” he says. More conversations are needed about unintended consequences, he says.
Levin agrees. He says little xenobots are fascinating in themselves, but they raise bigger doubts and greater possibilities. "You're finding a whole galaxy of weird new things."