Meet the Xenobots: a type of novel, living, and artificial product
Xenobots is named after the African clawed frog Xenopus laevis, where the stem cells are from. Each of these machines is less than a millimeter wide. Being programmable, they can move toward a target, pick up a payload, and heal themselves after being cut. Joshua Bongard, a computer scientist and robotics expert at the UVM who co-led the research, said, “they're neither a traditional robot nor a known species of animal. It's a new class of artifact: a living, programmable organism." Another co-author from Tufts University, Michael Levin also said that these are “entirely new life forms never seen in nature.” With the characteristics and functions above, these living machines are of vital importance in the fields of medicine, biology, chemistry and so on. According to Levin, they can be applied for many tasks “like searching out nasty compounds or radioactive contamination, gathering microplastic in the oceans, traveling in arteries to scrape out plaque” [1-4]
A four-legged Xenobot moving in an aquatic environment. Image from Douglas Blackiston, Tufts University
The creation of Xenobots: combination of supercomputer evolutionary algorithms and biotechnology.
There were mainly two steps to make Xenobots. First, with months of processing time on the Deep Green supercomputer cluster at UVM's Vermont Advanced Computing Core, the team – including the leading author and a Ph.D. candidate Sam Kriegman - used an evolutionary algorithm to create thousands of candidate designs for the new life forms, and selected the optimal ones. Then the team at Tufts, led by Levin and with key work by microsurgeon Douglas Blackiston, transferred the in silico designs into life. First they gathered stem cells, harvested from the embryos of African frogs, the species Xenopus laevis. They were separated into single cells and left to incubate. Then, using tiny forceps and an even tinier electrode, the cells were cut and joined under a microscope into a close approximation of the designs specified by the computer. Assembled into body forms never seen in nature, the cells began to work together [1,2,4].
*Left: A Xenobot blueprint produced by the evolutionary algorithm, in which green indicates skin cells and red indicates heart muscle cells. Right: the “living” Xenobot inspired by the computer’s design.
Image: Sam Kriegman, UVM
Characteristics of Xenobots: oriented delivery, clean degradation and self-healing.
In the tests, the skin cells formed a more passive architecture, while the once-random contractions of heart muscle cells were put together to make unified motion as designed by the computer, and aided by spontaneous self-organizing patterns - allowing the robots to move on their own. These reconfigurable organisms were shown to move in a coherent fashion - and explore their aquatic environment for days or weeks, powered by embryonic energy pool. Turned over, however, they failed, like beetles flipped on their backs. Later tests showed that groups of Xenobots would move around in circles, pushing pellets into a central location - spontaneously and collectively. Others were built with a hole through the center to reduce drag. In simulated versions, the scientists were able to repurpose this hole as a pouch to successfully carry an object [2,4].
Many robots made of materials like steel, plastic or concrete may cause ecological and human health problems, but Xenobots won’t. According to Josh Bongard, Xenobots can regenerate themselves. “And when they stop working - death - they usually fall apart harmlessly”. “When they're done with their job after seven days, they're just dead skin cells.” In addition, when Xenobots are cut almost in half, they can patch themselves back up and keep going. This is something typical robots cannot achieve [1-4].
* xenobots and their movement tracks.
Image source：University of Vermont
Future Shocks: science development vs ethical concern?
The research team not only created living robots, but also provided “a scalable pipeline for designing reconfigurable organisms.” However, many people are worrying about the implications of rapid technological change and complex biological manipulations. The lead author, Sam Kriegman, admitted that this research also raised a new ethical concern: future versions of such robots could be made with nervous systems and even cognitive abilities. But he added, “the important thing for me is that this is public, so we can have a discussion as a society and policymakers can decide which is the best course of action.” As for Levin, he considered people’s concern “not unreasonable”, but he also claimed “if humanity is going to survive into the future, we need to better understand how complex properties, somehow, emerge from simple rules.” Given this, their study actually is a direct contribution to getting a handle on what people are afraid of [1,2,5].
References:
[1] https://www.leiphone.com/news/202001/S5Oue6ZOCN3YR8ce.html
[2] https://www.uvm.edu/uvmnews/news/team-builds-first-living-robots
[3] https://mp.weixin.qq.com/s/zR9sf-AeHOKgS2l2BkANRg
[4] https://mp.weixin.qq.com/s/FNAuhlnjPte3GKarPhg8_g
[5] https://mp.weixin.qq.com/s/5QSrl1Aw5P2F0T-4D3eeqA