Originally published Jan 17, 2020

Scientists have unveiled the first ever "living robot," an organism made up of living cells, which can move around, carry payloads, and even heal itself.

"All of the computational people on the project, myself included, were flabbergasted," said Joshua Bongard, a computer scientist at the University of Vermont.

"We didn't realize that this was possible."

Teams from the University of Vermont and Tufts University worked together to build what they're calling "xenobots," which are about the size of a grain of salt and are made up of the heart and skin cells from frogs.



"The particular frog that we borrowed these cells from is known as Xenopus laevis," Bongard told Quirks & Quarks host Bob McDonald.

"But Xeno is also in Greek stands for alien, or unknown, or different, or new, and we think both interpretations apply to this new kind of technology."

Designed by supercomputer

Bongard's team used the Deep Green supercomputer cluster at the University of Vermont to figure out how to configure the cells to work as a robot.

The computer's "building materials" for the robot were heart cells, which could act as a kind of motor, and skin cells which could help provide structure for the organism.

Using an evolutionary algorithm, they told the supercomputer that they wanted these cells to achieve the simple task of moving across a petri dish. Then, over the next few weeks, the supercomputer assembled and then reassembled a few hundred simulated cells into different shapes to see which ones could achieve this task.



"The idea here is that you have these heart cells which basically increase and decrease in volume," said Bongard. "And if you put them all together they push and pull on each other and produce overall motion in the organism. We want obviously that motion to propel this new organism along the bottom of the petri dish."

The xenobot designs made by the supercomputer (top row) and the resulting organisms (bottom row). Skin tissue is represented by blue blocks, heart tissue is seen in red. (Douglas Blackiston and Sam Kriegman)

As the programs ran, the more successful designs were kept and refined, while failed designs were discarded. After hundreds of virtual tests, the most promising designs were passed on to a team at Tufts University to build in real life.

Working under a microscope, microsurgeon Douglas Blackiston carefully crafted these skin and heart cells together into the designs chosen by the supercomputer, making use of the cells' natural tendencies to stick to one another.

Xenobots act 'like very small sheepdogs'

Once they were built, these bots started moving around, just as the supercomputer predicted. But some of the ways they moved surprised the researchers — especially when they put multiple bots in the same dish.

"If... we add small pellets to the dish, the swarm of xenobots will act like very small sheepdogs. They will collectively push these pellets around and gradually push them into small piles," said Bongard.

"Now, why they do that is still a complete mystery to us."

Blackiston's team also wanted to see how the xenobots recover from injury, so they sliced one almost in half, and watched as the bot slowly stitched itself back together.

"After some more thought, it's not really that surprising because biological tissue has four and a half billion years' experience with dealing with everything that physical environment can throw at us," said Bongard. "So we sort of get this additional functionality for free."

The research was published in the scientific journal PNAS.

A swarm of xenobots (blue) work together to aggregate debris (red). (Douglas Blackiston and Sam Kriegman)

The ultimate motivation for making these these living robots was to create a robot that can go where traditional robots can't go, and leave less waste when their purpose has been met. For example, a xenobot could be used to deliver medication to a specific target in the human body, or be used to collect microplastics in the ocean.

"A lot of the applications we see at the moment are things like environmental cleanup and also clinical applications," he said. "Because these small bio bots are made up of 100 per cent living tissue, they're 100 per cent biodegradable and biocompatible."

Bongard also understands why some people are concerned with the idea of a living robot.

"There's no genetic engineering here, so we're not tinkering with viruses or the DNA of organisms. If you zoom in on a xenobot down to the level of an individual cell, you're looking at a normal frog cell," he said.

"In a way xenobots are just frogs, they just don't look anything like a frog."

Watch a xenobot move across a petri dish: