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Scientists turn frog cells into living machines

Scientists have taken a bold leap into the future with robots built from frog parts.

New research published this week in PNAS from Tufts University and the University of Vermont describes how frog stem cells can create a unique hybrid of organic and inorganic parts — living machines that power themselves.

“These are entirely new lifeforms. They have never before existed on Earth,” Michael Levin, study co-author and director of the Allen Discovery Center, explains in a new release. “They are living, programmable organisms.”

Dubbed xenobots, the new creations are less than a millimeter in size. But researchers say they can navigate, lift objects and even heal themselves.

“We sliced the robot almost in half and it stitches itself back up and keeps going,” co-lead researcher Joshua Bongard of the University of Vermont notes. “And this is something you can’t do with typical machines.”

A close-up of a xenobot. A manufactured quadruped organism, 650-750 microns in diameter — a bit smaller than a pinhead. (Photo: Douglas Blackiston, Tufts University)

For their designs, researchers used a supercomputer to create an “evolutionary algorithm,” essentially a program that models random configurations of skin and heart cells. Then those models are tested in a virtual environment under various conditions. One model might for example, be able to move under its own steam farther than others. That model then provides the basis for more designs, which are in turn, tested in virtual environments.

About 100 generations later, scientists choose the most efficient models to produce in the lab, adding early stage skin and heart cells from African clawed frog embryos.

In effect, it’s survival of the fittest for robots. And it’s where organic tissue reveals certain advantages. Heart cells, for example, have the ability to contract and relax on their own Those natural motions become a xenobot’s energy source.

An African clawed frog in a tank. The power for these robots is provided by stem cells taken from the African clawed frog. (Photo: Mary Jo DiLonardo)

And in case you’re fretting about a possible xenobot revolution, they also have an expiration date. The models function for between seven and 10 days  — long enough to complete their task  — before self-termination.

Besides, added co-author Sam Kriegman, “If you watch the video, it’s hard to fear that these things are taking over any time soon.”

Indeed, they are tiny and somewhat squishy., But the xenobots could take on some truly Herculean tasks in the future. Researchers suggest they may be deployed to clean microplastics from oceans and other remote places. Or they could detect toxins and gobble them up safely. Given their size, they may also be able to deliver drugs to a body or even scrape plaque from arterial walls.

Another potential use? If designed with blood vessels, nervous systems and sensory cells, xenobots could become basic eyes.

A diagram of a computer-generated xenobot. On the left, the anatomical blueprint for a computer-designed organism. On the right, the living organism, built entirely from frog skin (green) and heart muscle (red) cells. The background displays traces carved by a swarm of these new-to-nature organisms as they move through a field of particulate matter. (Photo: Sam Kriegman/University of Vermont)

Despite their promise, it’s hard to dismiss the ethical implications of grafting living cells to machines. Is there a point where “living, programmable organisms” become self-aware? And if so, how would we know?

“There are interesting ethical questions about the moral status of these xenobots,” Thomas Douglas of the Oxford Uehiro Centre for Practical Ethics, tells The Guardian. “I think they’d acquire moral significance only if they included neural tissue that enabled some kind of mental life, such as the ability to experience pain.

“But some are more liberal about moral status. They think that all living creatures have interests that should be given some moral consideration. For these people, difficult questions could arise about whether these xenobots should be classified as living creatures or machines.”

Scientists turn frog cells into living machines

Xenobots are hybrids of living frog cells and machinery — a unique hybrid of organic and inorganic parts that can power themselves.