Scientists have developed the first living robots capable of reproducing, a breakthrough in regenerative medicine. 

The millimetre-sized living machines, called Xenobots 3.0, are neither traditional robots nor a species of animal, but living, programmable organisms.

The computer-designed organisms are made from frog cell cells. A US team created them by gathering single cells in a Pac-Man-shaped mouth and releasing ‘babies.’ They look and behave just like their parents.  

The self-replicating, living biorobots can provide more personalized, direct drug treatment for injuries, birth defects, cancer, and other conditions. 

Xenobots 3.0 can gather hundreds of single cells, compress them and assemble them into 'babies' released from their Pac-Man-shaped mouths

Xenobots 3.0 are able to gather many single cells and compress them before assembling them into ‘babies.’ These babies can be released from Pac-Man-shaped eyes.


Xenobots can be described as a living and programmable organism that is neither a robot or a species of an animal.

They’re made from Xenopus livius, an African species frog. 

A computer designed the shape of their bodies to allow them to reproduce over several generations.  

Science has not found any animal or plant that replicates this behavior.

The Xenobots project will allow for the development of computer-designed organisms that can deliver intelligent drugs.  

Xenobots were created by computer scientists and biologists at Tufts University (UVM), and they have been described in a new study.

Xenobots 3 follow the original Xenobots. They were first reported as living robots in 2020.

Xenobots are able to walk. We discovered Xenobots which can swim. And now, in this study, we’ve found Xenobots that kinematically replicate,’ said study author Joshua Bongard, a computer scientist and robotics expert at the University of Vermont.  

“We have discovered that the living system, organisms and other systems contain a large unknown area. This is a huge space.” 

The team claims that Xenobots is helping to develop intelligent drugs delivery systems using computer-designed organisms. 

‘If we knew how to tell collections of cells to do what we wanted them to do, ultimately, that’s regenerative medicine – that’s the solution to traumatic injury, birth defects, cancer, and aging,’ said Michael Levin at Tufts University. 

“All these problems exist because we don’t know how predict or control which groups of cells will grow.” The Xenobots platform is a brand new way to learn.  

An AI-designed, Pac-Man-shaped 'parent' organism (in red) beside stem cells that have been compressed into a ball - the 'offspring' (green)

The ‘parent’ is an AI-designed Pac-Man-shaped organism. In red are stem cells which have been compressed into balls – the “offspring” (green).

In 2020, the scientists revealed they’d hand-built the original computer-designed Xenobots, adapted from stem cells of Xenopus laevis, a species of frog found in parts of Africa. 

What are STEM Cells? 

Stem cells, which are human cells with special properties, can develop into various cell types including muscle cells and brain cells.

They may also be able to heal damaged tissue in some instances.

Stem cells are divided into two main forms – embryonic stem cells and adult stem cells. 

Embryonic stem cells can become all cell types of the body because they are pluripotent – they can give rise to many different cell types. 

While adult stem cells may be found in most tissues of an adult, like bone marrow and fat, their ability to produce various types of cells is limited. 

Induced pluripotent stem cell (iPSCs), which are mature cells, have had their genetic programming reprogrammed so that they behave more like embryonic stem cell. 

Stem cells – which can turn into any tissue or organ – were harvested from the embryos of the frogs and left to incubate.

The microsurgeon joined the cells with tiny forceps using an electrode.

Cells were then assembled to form body shapes never before seen in nature. They began to function together thanks embryonic energy. 

They demonstrated that bots could be programmed to deliver medicine to specific points in the body.    

This new generation – Xenobots 3.0 – uses stem cells from the same frog species. 

Xenobots 3.00 can collect hundreds of individual cells, compile them and assemble them to form ‘babies.’ These babies are released from Pac-Man-shaped ears.

These Xenobots, which look and behave just like their parents’, are then renamed Xenobots a few days later. 

And then these new Xenobots can go out, find cells, and build copies of themselves – and the process happens over and over again. 

These embryonic stem cell would normally develop into skin in a Xenopus livius frog. 

Levin stated, “They would sit on the outside of an a tadpole keeping out pathogens and redistributing mucus.”

“But, we are putting them in a new context. It’s giving them the chance to see their multicellularity in a new light.

“These cells possess the same genome as a frog but are free from turning into tadpoles. Instead, they utilize their collective intelligence and a plasticity to accomplish something amazing.

Close-up of three young African clawed frogs (Xenopus laevis). Embryonic stem cells from this species were used to create the 'Xenobots'

Three young African clawed frogs, Xenopus levis (close-up) Embryonic stem cells of this species were used in the creation of the Xenobots.

On its own, the Xenobot parent, made of some 3,000 cells, forms a sphere – but it can’t reproduce effectively over several generations.

‘These can make children but then the system normally dies out after that,’ said Sam Kriegman at Tuft’s. It is very difficult, in fact, for the system to continue reproducing.

So, the team used a computer – specifically an artificial intelligence (AI) algorithm on the Deep Green supercomputer cluster at UVM.

The algorithm was able to test billions of body shapes in simulation – triangles, squares, pyramids, starfish – to find ones that replicate.

Kriegman stated, “We asked UVM’s supercomputer to determine how to alter the form of the parents’ initial parents. The AI produced some bizarre designs after months of working hard, one of which resembled Pac-Man.” 

“It is very difficult to understand. Although it looks simple, this is not what a human engineer would have thought of. Is it really necessary to have one small mouth? Why not five? Doug was able to build these Pac-Man-shaped Xenobots from the information. 

A simulation of a computer designed organism collecting stem cells in the environment (left) accurately predicts the behaviour of the system in vitro (right)

The behaviour of an in vitro computer-designed organism that collects stem cells from the environment is accurately predicted by this simulation (left).

‘Then those parents built children, who built grandchildren, who built great-grandchildren, who built great-great-grandchildren.’ 

Also, Pac-Man’s design significantly extended the lifespan of the generations.

In response to any ethical concerns the public might have, the team stress Xenobots are entirely contained in a lab, are easily extinguished, and are vetted by federal, state and institutional ethics experts. 

Bongard stated that this is a great system to learn about self-replicating systems. “We are morally bound to study the conditions that allow us to control it, direct and douse it.

For society, it is important to understand and study how the world works.    

Proceedings of the National Academy of Sciences has published the team’s research. 


A breakthrough stem cell injection could one day help cure faulty hearts, according to scientists.

The cells are unable to adjust to the new environment and previous attempts at regenerating hearts have failed.

University College London scientists have found a method to maintain stem cells longer in the body by growing them onto miniature spheres.

Because of their small size, microspheres can easily be injected directly into the heart muscle. Their method was proven to work in heart failure.

Read more: Scientists behind new stem cell tech hope it could cure heart failure