What comes to mind when you think of machines? Perhaps structures made of metal, plastic, or ceramics. What if I told you scientists have built tiny robots from frog cells that can move, remember things, and heal themselves? I am talking about Xenobots 2.0, the world’s first living robots, which were made using cells derived from frog embryos. They are named after the African clawed frog (Xenopus laevis) from which they were created. Biologists at Tufts University and computer scientists from the University of Vermont came together to develop these living robots from frog stem cells using artificial intelligence. Stem cells are specialized cells that can develop into different cell types. In the case of xenobots, the stem cells were transformed into frog skin (green) and heart cells (red).
What makes these organisms so cool is that they are versatile in their structure and function. Researchers used supercomputers to model the cellular building blocks of xenobots. Imagine cells to be like LEGO® bricks that are used to make specific structures. Using artificial intelligence, the anatomy of the robots is generated by computers. In addition, a computer simulation is used to design the actions that a xenobot is capable of. The computer then selects the designs that perform best in the simulations, and these blobs of cells are carved into the shapes designed by the computer using minute tools. These microscopic robots live in freshwater between 40-80 degrees Fahrenheit, and they consist of about 5,000 cells and are approximately 0.7 millimeters in size. Xenobots contain a pre-loaded source of nutrition, including proteins and fats, that can sustain them for over a week. However, in environments rich in nutrients, they can live for months.
One example of a specialized structure that xenobots have are stub-like appendages that resemble legs (see above image). These structures, which were described by researchers in their recent paper, open up endless possibilities for the functions of xenobots. The current version of xenobots move around by swimming and “walking,” and they are able to push/carry objects with them. They can even navigate around particles in their surroundings, almost like a maze, to avoid bumping into obstacles. Xenobots can also communicate with one another and move together as a swarm (see video below). Amazingly, they can even heal themselves when they are injured by closing the wound.
The development of these living robots is way beyond just a cool science experiment; xenobots could have incredible real-life applications. Traditionally, robots were built to do tasks that are too dangerous for humans or tasks that are repetitive and programmable. This concept can be applied to xenobots as well. Their tiny size enables them to enter the body to perform operations that may not be possible for humans. They are also made entirely of biological material, so they will automatically be degraded by the body after they are used. Potential medical applications include entering arteries and scraping off harmful fat deposits, genetically changing cancer cells back to normal cells, and delivering medicine to specific organs. Other potential applications could be to clean up radioactive waste or clear oil spills and microplastics from oceans. Since xenobots are biodegradable, they will not pollute the environment. In addition to these applications, the complex structural organization and functions of xenobots can be used to understand the biology and evolution of multicellular organisms.
All of this is great, but what if these little frog robots turn rogue and take over humans? Or worse, could they be weaponized and misused? Here’s what the scientists who made xenobots had to say about it: “At the moment though, it is difficult to see how an AI could create harmful organisms any easier than a talented biologist with bad intentions could. Despite this, we believe that, as this technology matures, regulation of its use and misuse should be a high priority.”
More research is certainly needed for xenobots to have mainstream applications. However, for now, we can marvel at the groundbreaking wonders that were made possible by integrating biology and computer science.
Kriegman, S., Blackiston, D., Levin, M., & Bongard, J. (2020). A scalable pipeline for designing reconfigurable organisms. Proceedings of the National Academy of Sciences USA, 117, 1853-1859. https://doi.org/10.1073/pnas.1910837117.
Kriegman, S., Blackiston, D., Levin, M., & Bongard, J. (2021). Computer designed organisms.