Living robots made from frog skin cells can sense their environment

A microscopic, living robot that may heal and power itself has been created out of frog skin cells.

Xenobots, named following the frog species Xenopus laevis that the cells result from, were first described last year. Now the team behind the robots has improved their design and demonstrated new capabilities.

To create the spherical xenobots, Michael Levin at Tufts University in Massachusetts and his colleagues extracted tissue from 24-hour-old frog embryos which formed into spheroid structures after minimal physical manipulation.

Where in fact the previous version relied on the contraction of heart muscle cells to go them forward by pushing off surfaces, these new xenobots swim around faster, being self-propelled by hair-like structures on the surface. They also live between three and a week longer than their predecessors, which only lasted about a week, and have the capability to sense their environment somewhat, turning red when subjected to blue light.

“The essential finding here is that whenever you liberate skin cells from their normal context, and you provide them with an opportunity to reimagine their multicellularity, they are able to build other things than what they normally build,” says Levin. “If you ask me, the most exciting things here is plasticity. This idea that even normal cells, not genetically modified, with a standard frog genome, are actually with the capacity of building something very different.”

The xenobots, which are between 25 % and half of a millimetre in proportions, operate in robot swarms, and therefore several individual xenobots could work together to complete an activity.

Read more: Robot swarm inspired by cells will keep moving whether or not its parts fail

Because they’re created from cells, the xenobots eventually break apart and so are totally biodegradable, says team member Douglas Blackiston, also at Tufts University. He therefore hopes that they works extremely well for biomedical and environmental applications.

“Roboticists have been looking at swarm intelligence for a long period, biologists have been studying swarm intelligence in organisms. That is something in between, that i think is kind of interesting,” says team member Josh Bongard at the University of Vermont. “It sort of suggests, to me at least as a roboticist, is this a better way to making swarms of useful machines than it is to create swarms out of traditional robotic parts?”

Previous attempts at creating living robots, for instance a wirelessly handled cockroach, have involved manipulating live animals, raising ethical concerns. Xenobots differ from these because they’re made totally of living cells.

“The approach here’s maybe ethically minimal problematic because everything is in vitro, they just focus on cells, they haven’t any neurons, so it’s not an animal,” says Auke Ijspeert at the Swiss Federal Institute of Technology at Lausanne, who wasn’t mixed up in research. “It’s really cells that they manipulate, therefore i think it is maybe the cleanest way.”

But are xenobots similar to living organisms or traditional robots? “I don’t feel any nearer to an answer. Whether they are robots, whether these are frogs, whether they are something else entirely,” says Bongard.

Journal reference: Science Robotics , DOI: 10.1126/scirobotics.abf1571

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