Researchers behind the world's first living robot have found a way to make it reproduce — by shaping it like Pac-Man

• The world's first living robot is now able to replicate itself in a unique way.
• Xenobots are robots made from the stem cells of the Xenopus laevis, an African clawed frog.

Scientists that created Xenobots — the world's first living robots — have found a way to efficiently form the bots to reproduce themselves on their own.

The Xenobots are formed from stem cells of the Xenopus laevis (an African clawed frog), the cells of which have tiny little hairs called cilia to help them move around a petri dish. Scientist Sam Kriegman told Insider that, while people may think of large industrial or metallic figures as robots, the term really refers to any machine that does "physical, useful work" in the world.

Kriegman worked on the Xenobot project along with researchers affiliated with the University of Vermont, Tufts University, and Harvard University's Wyss Institute for Biologically Inspired Engineering.

"We tried to figure out what useful work they could do, and one of the things that we came up with was to clean up the dish," Kriegman said.

The researchers placed dye particles and silicone-coated iron beads into the petri dish and observed the movement of the little Xenobots, observing that they were piling up the debris, Kriegman said. He described the Xenobots as bulldozers that move around and push stem cells into piles.

Kriegman said his colleague Douglas Blackiston then repeated the process by placing additional cells – the same kind that the Xenobots are made of — to see how the bots would react.

"I said, 'Oh my God, that's amazing. What happens when they make the piles. What do the cells become when they're piles?' We didn't know," Kriegman said. "We found out by letting those piles develop over the course of a few days, and then bringing them into a new dish and seeing if they can move."

He added: "And it turns out that is possible."

This pointed towards the piles becoming "offspring" of the stem cells, growing their own cilia and operating on their own.

"If there's enough of the stem cells in a pile, they will start to develop and will compact together in a sphere," Kriegman said. "They'll grow cilia, and that allows them to move, and in some cases, also make additional piles, and those piles become their offspring."

Kriegman said, at first, the replication was happening "spontaneously," so researchers used artificial intelligence to figure out the best shape for the Xenobots to replicate on a more consistent basis to have better control.

"We built a computational model that simulates the stem cells and everything inside of the computer," Kriegman said of the process.

They discovered that a "Pac-Man" shape yielded the best results to ensure the Xenobots were able to create more, thus engineering the shape of the actual Xenobots into the more efficient form.

"It turns out that that design is at least two to three times better than just the natural state," Kriegman said. "So they created children that made grandchildren, that made great-grandchildren, and great-great-grandchildren. So, four rounds of replication with the 'Pac-Man' design."

For now, the Xenobots are contained to the petri dishes of the lab, but Kriegman said biologists and roboticists hope the project could give insight into how some animals can regenerate lost parts while some cannot, like how humans are able to regenerate parts of their liver, but salamanders can regenerate entire limbs.

He said the next step for the Xenobots would be to give them some sort of sensory organs — for instance, a way to see.

"Right now, they're essentially swimming around with their eyes closed," he said. "They're just balls of motors."