Robots made of living animal cells

It feels like some sort of line has been crossed, or at least blurred: researchers in the US have created robots made entirely from living cells.

A time-lapse recording of cells being manipulated and assembled, using in silico designs to create in vivo living machines, called xenobots. 
CREDIT: Douglas Blackiston, Tufts University

“These are novel living machines,” says Joshua Bongard of the University of Vermont, one of four authors of what might turn out to be a historically significant paper published in the journal Proceedings of the National Academy of Sciences.

“They’re neither a traditional robot nor a known species of animal. It’s a new class of artefact: a living, programmable organism.”

The xenobots, as they’ve been dubbed, are made from frog embryo cells and are just one millimetre wide. They were designed using a supercomputer at Bongard’s university and then assembled by colleagues working at Tufts University in Massachusetts.

The researchers see them having multiple applications, including searching for toxic compounds in contaminated sites, harvesting microplastics from the ocean, or being deployed as drug-delivery mechanisms inside the body.

All of which will probably prove extremely useful, but shouldn’t distract from the principal outcome here: the creation, for the first time, of entirely new biological machines that could accurately be described as bespoke lifeforms.

Indeed, Bongard and colleagues note in their paper, once refined a little more, the process of creating these unique living robots could be fully automated – a product of artificial intelligence and machine learning that requires no human intervention at all.

For the moment, however, a level of direct intercession is still required.

The creation of a viable xenobot begins with multiple computer simulations involving models of frog skin and cardiac cells. The computer is tasked with designing a bot that has specific desired functions, such as locomotion.

AI takes over, using an algorithm to churn through thousands of iterations until the desired result is produced.

The model is then adapted by microsurgeons, using a stock of individual frog cells gathered from an African species, Xenopus laevis, that have been grown in the lab. 

The researchers report that the cells, thus joined together, gradually began to work in harmony, with the skin cells providing a structural framework and the cardiac cells synchronising their trademark contractions.

The proof-of-concept bots detailed in the paper moved around a water-filled container – looking for all the world as if they were exploring it – for several days or weeks before expiring.

Living cells, Bongard notes, necessarily die after a given period, but many types also have the inbuilt ability to regenerate or reproduce. This lends xenobots a couple of interesting properties – depending on the design and the type of cell used, they can either have short, finite lifespans, or they can be effectively immortal.

“The downside of living tissue is that it’s weak and it degrades,” says Bongard. “That’s why we use steel. But organisms have 4.5 billion years of practice at regenerating themselves and going on for decades.” 

The research was funded by the US Defence Advanced Research Projects Agency through a project known as Lifelong Learning Machines.