Living robots designed by computer and built from stem cells have started to reproduce in a breakthrough which could lead to self-replicating machines, scientists have said.
In 2020, US researchers programmed a supercomputer to come up with blueprints for entirely new organisms using virtual skin and heart cells, which they then built in real life.
The microscopic animal-machine hybrids, dubbed "xenobots" were able to move on their own, and remain "alive" for weeks powered by their embryonic energy stores.
Now scientists have shown that if the xenobots are placed in a petri dish with embryonic frog stem cells, the bots sweep the cells up into little round piles which morph together into new organisms and also begin to move.
The process, known as kinematic replication, has been seen in molecular machines but never at higher levels of biology. Multicellular organisms typically reproduce by splitting, budding, or giving birth.
Organisms resemble Pac-Man
After discovering the bots could reproduce, the researchers went back to their computer to design a better shape for reproduction, eventually coming up with an organism resembling Pac-Man, the 1980s arcade game.
The robots are built from living cells using tiny forceps
Scientists videoed the "c-shaped" parents collecting the cells in their "mouths" before building the "offspring" from the loose cells in an entirely new form of biological reproduction different from any animal or plant known to science.
“I was astounded by it,” Professor Michael Levin, of Tufts University, Massachusetts, told the US news site CNN.
“Frogs have a way of reproducing that they normally use but when you ... liberate (the cells) from the rest of the embryo and you give them a chance to figure out how to be in a new environment, not only do they figure out a new way to move, but they also figure out apparently a new way to reproduce.”
Xenobots are less than a millimetre (0.04 inches wide) and are assembled from cells taken from the African clawed frog - Xenopus laevis - from which they get their name.
Scientists first used the Deep Green supercomputer cluster at the University of Vermont to create an algorithm that assembled a few hundred virtual skin and heart cells into a myriad forms and body shapes, for specific tasks.
Xenobots could help clear arteries
Based on the blueprints, a team of biologists gathered stem cells, harvested from the embryos of the African frogs and used tiny forceps and a miniature electric knife to cut and join the cells under a microscope into a close approximation of the designs specified by the computer.
Once assembled into forms never seen in nature, the cells began to work together. The skin cells formed a "body" while contracting heart muscle cells were repurposed to create a forward motion, allowing the robots to move on their own.
Researchers are hopeful the xenobots could one day be programmed to move through arteries scraping away plaque, or swim through oceans removing toxic microplastic.
And now it is proven they can replicate, they could repair themselves if damaged or torn, scientists hope.
The research was published in the journal PNAS.