Xenobots: The Rise of Living Machines

On the 15th of January 2020, researchers at the University of Vermont and Tufts University were able to synthesize the first-ever “living robots”. What do the words “living robots” even mean? Are these cyborg creatures from doomsday movies? Is there a reason to fear and to feel possessive about the human race? A rather anticlimactic explanation is in store.

The “living robots” here refer to xenobots. A xenobot (deriving its name from a species of frog, Xenopus) is an entirely new kind of microbot, programmed by a supercomputer and composed purely out of skin and heart cells of frog embryos. A microbot is a kind of robot that spans less than 1 mm across.

So, what’s so special about them? Other than the fact that they are made up of a combination of heart and skin cells, a computer programs and maps out their shape and structure in just the right manner so that they perform functions as required. This means that they are custom designed for each and every application. 

When these robots were first conceived, scientists recognized two types of cells in organisms:

  1. Heart cells, which naturally have the ability to contract, through which they can generate movement.
  2. Skin cells, which would give the robot the required structure. Different arrangements of these cells could give robots with variable structural parameters like the center of mass and the moment of inertia.


Scientists realized that we can achieve motion by a balanced proportion of cells at just the right places, let’s say in the forward direction, then it is also possible to make the robot twist and turn as per the will of the “programmer.” Since these creatures are somewhere around a millimeter wide, they may contain hundreds of cells, so finding out where cells should exactly be placed was achieved via computer simulations. Once a suitable simulation of just the right kinds and numbers of the two types of cells was prepared, the scientists then painfully pieced the robots together by microsurgical methods, mostly by hand.

As predicted, the bots moved in the direction intended. This wasn’t a coincidence either. When the bots were placed on their backs, they lost their ability to move. This meant the initial orientation was also an important parameter when constructing the robots.

Subsequently, a ring-shaped xenobot was also made. In the gap created, a small molecule could easily be placed, making it possible for the xenobot to act as a delivery service for molecular objects. This invention could have far-reaching implications in the field of nanomedicine and diagnostics.


Fig.1 Xenobots and the cells they attempt to mimic


Evolutionary algorithms were used during the simulation process to construct the microbots. In a nutshell, these algorithms work in the following way. They are given an end-goal. In our case, let’s assume a xenobot’s motion in a circle. A large number of samples is made to achieve that goal. Based on how much they are able to move, they are assigned a score. The top-scorers get their traits intermixed and mutated, and there we have our next generation of robots. The process goes on and on until we achieve a robot which can move in a circle, almost perfectly. Cycling through all the permutations in such an algorithm is a massively time-consuming process, and supercomputers help us speed it up.


Coming back to our xenobots, the scientists managed to make these robots move all over their Petri dishes in all sorts of trajectories, a phenomenon that appeared as a surprise to the scientists was the bots’ ability to self-heal themselves once damaged. This opens a window to making robotic devices that are not only tough and unbreakable but which also repair themselves upon being damaged!


To make things just a little stranger, they observed something that biologists call “emergent behavior,” that is, the bots behaved differently with other bots in the vicinity, as compared to how they did when they were alone. The brain cells, for example, are a very good example of how emergent behavior is such a big deal. When isolated, they are capable of nothing more than conducting small electrical impulses in one direction. United, however, they are capable of transmitting information across several cells, making feedback loops and complex thought processes possible!


Xenobots demonstrated emergent behavior when one of them changed its “programmed” trajectory and moved around other clusters of other xenobots, either to move around them or with them. They interacted with each other in ways only seen in purely living systems. This came as a huge surprise to computer scientists and engineers who were unaware of this element of biological uncertainty.


The report of this invention has sent the scientific world into a tizzy. A wide array of applications of these tiny creatures (it would be fair to call them that, wouldn’t it?) have been proposed. Some of these applications include targeted drug delivery, cleaning radioactive and plastic waste in hard-to-reach places, and doing some other specialized things which are not eco-friendly to do with the current-gen robotics, which use plastics and metal and silicon to piece up, and are, therefore, harmful for the environment. In addition to this, making xenobots, in a way, serve as a sandbox of sorts, helping run controlled simulations of living organisms, eventually understanding cell structure, helping us know more about our bodies. This additional information, especially that derived from studying self-repair in these microbots could help us learn about aging and longevity in a lot of different ways. It can also help us understand and imitate the regeneration of our own body parts.


However, like every invention that accelerates human progress, the invention of xenobots also brings with it a fair share of controversy. The main concerns here are ethical. Even though scientists claim that these creatures are no smarter than the biologists and computer scientists who created them, it’s safer to be skeptical at this point. Due to the randomness stemming out of the biology of these robots, we are seeing and can expect to continue seeing unexpected results. 

Moreover, futuristic ethical concerns may also arise. Will these things demand their own rights? Will we lose control over them? Will they be legalized by government authorities in the first place, if they are being used for the sole purpose of targeted drug delivery? (take CRISPR/Cas gene-editing for example. You can read more about it here.) One can only hope that this invention does not die a lonely death in some laboratory, due to the lack of foresight of policymakers.

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