A team of scientists has
repurposed living cells (scraped from frog embryos) and assembled them into
entirely new life-forms. These millimeter-wide ‘xenobots’ can move toward a target,
perhaps pick up a payload and heal themselves after being cut. The new
creatures were designed on a supercomputer at UVM and then assembled and tested
by biologists at Tufts University. This research designs completely biological
machines from the ground up. With months of processing time on the Deep Green
supercomputer cluster at UVM's Vermont Advanced Computing Core, the team used
an evolutionary algorithm to create thousands of candidate designs for the new
life-forms. Attempting to achieve a task assigned by the scientists like
locomotion in one direction the computer would, over and over, reassemble a few
hundred simulated cells into myriad forms and body shapes. As the programs ran
the more successful simulated organisms were kept and refined, while failed
designs were tossed out. After a hundred independent runs of the algorithm, the
most promising designs were selected for testing.
Next, researchers transferred the
in silico designs into life. First they gathered stem cells, harvested from the
embryos of African frogs, the species Xenopus laevis. These 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. The skin cells
formed a more passive architecture, while the once-random contractions of heart
muscle cells were put to work creating ordered forward motion as guided by the
computer's design, and aided by spontaneous self-organizing patterns allowing
the robots to move on their own. These reconfigurable organisms were shown to
be able move in a coherent fashion and explore their watery environment for
days or weeks, powered by embryonic energy stores. Turned over, however they
failed and later tests showed that groups of xenobots would move around in
circles.
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