Mar 31, 2021 - Science

Frog cells can form a self-powered living robot

GIF of xenobot
Xenobot. Credit: Douglas Blackiston/Tufts University

Frog cells can gather together on their own to create tiny living moving robots.

The big picture: Researchers are trying to build soft robots, biodegradable ones and even living versions in hopes of using the machines in hard-to-access disaster zones, within the human body to deliver medicine and for environmental cleanup.

What they're saying: "The line between biology and robotics is already starting to blur," Douglas Blackiston, a senior scientist at the Allen Discovery Institute at Tufts University and author of the new study, says.

  • "We're creating something new that doesn’t exist in nature and we're building it for work and to solve a problem."
  • "Our work swings the pendulum and says you can do the same [robot] designing with 100% biological materials."

How it works: Last year, researchers demonstrated how cells harvested from developing frog eggs can be arranged into so-called xenobots with the help of algorithms.

  • Different arrangements of the cell types (skin or heart muscle) are simulated in a virtual world created by University of Vermont computer scientists Josh Bongard and Sam Kriegman to figure out which cell combinations can move in an organized way.
  • Blackiston then sculpts the living robot — a few thousand cells in a mass the size of a quarter of a poppy seed — by moving or removing cells to get the desired movement, powered by the muscle cell contraction.

What's new: In research published Wednesday in Science Robotics, the team reports the frog skin cells on their own will form spherical masses of cells and use cilia, structures on the cell surface that resemble hair, to motor around. (Typically cilia help to keep mucus distributed on a frog's skin.)

  • The tiny bots move in spirals, straight lines or swarm around particles they encounter.
  • The self-powered living robots can live in water using nutrients from the yolk for about 10 days and heal themselves if cut or torn, the team reports.
  • When the researchers introduced a protein, the cells could sense when they'd been exposed to blue light and turn red.
Xenobots covered in cilia
Xenobots covered in cilia. Photo: Douglas Blackiston/Tufts University

What's next: Future goals include using these newly discovered capabilities to better control the living robots' movement, attempting to make them from different animal cells, including eventually human cells, and modifying the robots' genetics to sense more in their environment, Blackiston says.

  • Ultimately, the researchers envision using the living robots to deliver drugs in the body, assess contamination in water, or clean up microplastic particles.

What to watch: The living robots can't reproduce and they don't have neurons but if such attributes are added, it would raise thorny questions about how we define life and cognition, Blackiston says.

  • "We’re removed from that but eventually that question will creep in: what right do we have to design life and what should that regulation look like?"
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