Xenobots: The Age of Biological Robots

The ability for a robot to move through its world, pick up pieces and stick them together to create a working copy of itself has yet to be seen. We’re showing that if you build robots out of biological cells instead of mechanical parts, then building these kinds of self-replicating machines might not be as difficult as we had once thought. These types of xenobots can self-replicate in an interesting and unique way. Some may or may not call this reproduction or replication, but the result of it is that xenobots build more xenobots.


A post-doctoral fellow at Tufts University and Harvard University shares his role in the xenobots project, coming up with AI software that can help us better understand and better control and design xenobots to do what they want them to do. When we go to design a robot, we investigate the world and pick a familiar object and copy it. Most robots look like dogs or humanoids – we can’t really help it. But AI doesn’t share our design biases and so the AI came up with many different shapes.

One of them looked like the iconic video game character, Pac-Man. It’s just more or less a hockey puck, a disc with a little mouth cut out of it. When this design moves around the dish, it creates much larger piles out of the cells we provide it. So, AI is generating xenobots and so on. We achieved great-grandchildren using the Pac-Man shape and that Pac-Man shape was designed by AI, so that’s very interesting.


When we first presented the xenobots to the world, we used two kinds of Lego bricks made from frog cells, and we had heart muscle, which acted like little pistons – it contracts and relaxes like a piston would, and skin cells that were just passive. So, we asked an AI program to put together these two kinds of building blocks such that it would result in behavior, some kind of little device made from these blocks, that would move in certain ways or carry a pellet across its dish or act together in swarms.

In the newer research, we sped up this process of manufacturing the xenobots by taking advantage of the inherent properties of cells, but cells have other kinds of motors and sensors and building blocks that we can exploit for building mobile little devices that we might call robots. One of those is called cilia, which when used is much faster than heart muscle motors. So, we created robots using cilia and skin forming cilia is well-known in biology, but it hasn’t been used to create a robot, something whose behavior could be used for useful work.

Ethical Implications

Now, a world full of custom planet-saving xenobots sounds cool— but you may have already asked yourself about the ethical implications for fashioning an entirely novel form of life. And you’re not alone. The team has fully acknowledged that future iterations of xenobots could include nervous systems, blood vessels, or even reproductive parts. And it’s these additions that are prompting many to wonder if xenobots should be considered more than just machines.

The Future

There’s a quote that says, “If a scientist tells you something’s dangerous, everybody believes it”. If a scientist tells you something’s safe, nobody believes it. We don’t always make that clear in interviews to the public. So, I think if you are an average citizen, I understand where the memes come from, I understand where the fear comes from when you see just a headline that says, “Scientists create a biological robot capable of self-replicating,” but what gets lost is all the detail, right? It’s the need to get the public excited about science and show them what’s really coming down the line, but also sometimes a failure to communicate exactly how that’s happening without giving them sort of the sci-fi, ‘Terminator’ version of everything that we’re working on. The part that excites me as a scientist is this idea that the line between synthetic and biological materials and building these is beginning to blur. So traditional robotics, the word extends a hundred years ago to a Czech play. The original robots in that work were built from organic material. I think there’s a lot of applications, where living materials might be very good at doing something that artificial materials are not. And then more philosophically, the part that really excites me is how AI works and how programming works. There’s a question of, “What if an AI can design a specific heart for a specific person?” So, it can understand your genetic basis, your racial background, your health habits, your weight, and perhaps there is a design that may, in fact, be more efficient for a specific human than a typical heart. Do we feel comfortable allowing AI to have agency in that process and to hand over that aspect of what we would consider sort of traditional medicine to an artificial intelligence?

I think that’s an interesting and fantastic philosophical question that I don’t have the answer for, but it’s something we’ll be increasingly confronted with in the years to come.

Future Directions

There’s also the tiny fact that the research is partially sponsored by DARPA’s lifelong learning machines program. Which again, has left some observers questioning the future direction of this research. However, the research team is open and encouraging of these ethical discussions in the public domain in the hope that policymakers can keep up and implement the right regulations as this science progresses. Right now, xenobots are still basic, and currently restricted in their reproductive abilities. And in terms of scalability, as we’ve just learned, these bots aren’t exactly easy to create, requiring hours of microsurgery just to create one.


The next phase of the research is to develop a xenobot capable of carrying a payload using a patient’s cells to deliver medications deep within the human body without eliciting an immune response. So ultimately, these xenobots are just the first steps in trying to understand how life starts, perhaps one day providing scientists with the ability to control exactly how life forms. For more robotics topics, check out this Focal Point on a robotics lab that’s investigating the idea of artificial consciousness. Are there other exciting innovations that you’d like to see us cover? Let us know in the comments below and thanks for reading.

Leave a Reply