Tiny living robots made from human cells surprise scientists

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In 1920, Czech playwright Karel Čapek wrote a science-fiction play called "R.U.R.", which stood for Rossum's Universal Robots, and which was set in the year 2000. This was the first time the word robot had been used. These robots were more like androids, purely organic beings, instead of metallic walking computers. However, they looked like the tin man from the Wizard of Oz. Engineers have since been working on creating microscopic robotic machines to work at the cellular level. But in recent years, scientists have also gone back to the RUR days of organic robots. They are microscopic and composed of living cells. How does that work?

Robots in the play "R.U.R." (Wikipedia)

The benefit of such devices, if they were to exist today, is thought to be in drug delivery, surgery, diagnosis, monitoring of diseases like diabetes, and even cleaning the oceans. In 1959, Nobel Prize winner Richard Feynman even conceived of using tiny machines to more efficiently create new chemicals by directly manipulating atoms. 

What if it microscopic robots didn't require mechanical parts and were disposable? In 2020, teams at the  University of Vermont Advanced Computing Core and the Center for Regenerative and Developmental Biology at Tufts University developed organic microscopic robots. The Vermont group created computer models of potential cell clusters of skin and heart cells from the African frog Xenopus laevis. Skin cell properties were used to help build proposed structures in many shapes because skin cells are made to do that. Heart muscle cells flex, and their properties were added to the "evolutionary algorithm" in the software to determine various functions like movement. The idea was to see which shapes and configurations of these cells would theoretically work together in clusters to create functional organic robots.

100 computer models for functional cell clusters

(adapted from Proceedings of the National Academy of Sciences)

(red=heart cells, blue=skin cells)

After many computer trials, the most successful models were handed off to Tufts U. Scientists there then peeled apart cells from Xenopus embryos and put them in groups. The cells clumped together to form a cluster of many cells. Then, with tiny tweezers, the researchers poked and prodded the clusters into the shapes of the computer models. Each one took several hours to build, but eventually these became the living, moving "xenobots", named after the frog source. 

Computer model and colorized xenobot cell cluster (University of Vermont)

Just under a millimeter (0.04 inches) wide, they are about 3 times the size of a period in Times New Roman 12-point font. Tufts U researchers observed them move about in Petri dishes for days or weeks until their internal energy supplies ran out. Movement is caused by hair-like projections called cilia, which move like paddles. Some xenobots had holes in them designed to carry material, but others without holes spontaneously pushed pellets of material together as they moved.

Xenobot spinning, moving, joining other xenobots in a Petri dish (YouTube)

When xenobots were damaged even to the point of being cut nearly in half, they repaired themselves.

Clip from YouTube

But even more amazing is that these clumps of cells were able to reproduce. Instead of just splitting each cell in the cluster, they worked together to gather other cells in the area. Those new clusters became new xenobots that do the same at the "parents". See what the designer has to say:

From YouTube shorts

More recently, in November 2023,  the Tufts U researchers have created "anthrobots", which are cell cluster robots made from human cells, specifically adult lung cells. Instead of 3-4 days, these took 7 days before they showed movement. Also,  from 2,281 of these, about half consistently don't move at all even after 3 weeks, even though they have cilia. The thing is, since they were from lung tissue, the cilia formed on the inside of the clump like it was the lining of the trachea. By adjusting the chemical composition of the medium they lived on in the Petri dish, the researchers changed that to the outside.

Cilia shown in yellow (from Advanced Science)

Anthrobots tend to have 4 types of motion: circular, linear, curvilinear, and eclectic. Examples are shown below from the researchers paper.

From Advanced Science, 2023

Anthrobots come in 8 unique cluster shapes, and each is correlated with a certain amount of cilia. What's more, they follow a scratched line in the Petri dish, which might be useful in later medical research if these are used to follow tissue cuts for repair to take place. See below microscopic tracking of the scratch outlined in yellow and the anthrobot path in pink.

From Advanced Science, 2023)

Taken to the next level, anthrobots have also been shown to fix damaged nerve tissue by forming "superbot" bridges. In the photos below, the top one shows a bridge formed in a cut. The bottom picture simply shows the superbot in red and nerve tissue in green.

From Advanced Science, 2023

Considering how important it is to repair nerve tissue, which normally is next to impossible, the usefulness of these organic robots is pretty clear.

Here's a nice 5-minute video that summarizes this blog article.