Feb 12, 2022 - Science

A robotic "fish" powered by human heart cells

Biohybrid fish. Credit: Michael Rosnach, Keel Yong Lee, Sung-Jin Park, Kevin Kit Parker

Human heart cells make a new robotic "fish" swim, scientists reported this week.

Why it matters: The engineering feat is a step toward creating artificial muscle that could one day be used in medicine and in soft robots. In the nearer term, the researchers say the robotic fish offers a platform for studying how heart muscle works in humans.

How it works: A team led by Kit Parker, a professor of bioengineering and applied physics at Harvard University, put sheets of human heart muscle cells on each side of the tail of a fish skeleton made from paper and plastic, and covered in gelatin. (The design builds on their earlier work creating a robotic stingray.)

  • A cluster of cells sends signals that synchronize the stretching and contracting of the muscle cells, the researchers report in a study published Thursday in Science.
  • When cells on one side of the fish contract, the cells on the other side stretch, and so on, creating a self-sustaining swimming motion.
  • It's a "tour de force in engineering," says Barry Trimmer, a professor of biology at Tufts University, who studies how to engineer artificial muscle using insect cells and wasn’t involved in the new research.

A challenge for making a bigger muscle is how to keep the cells alive. In mammals, vasculature and blood vessels support the cells, but a similar design hasn't been developed to give cells access to a blood supply in artificial muscle.

  • The fish, fed by nutrients in the swimming medium, maintained their swimming speed and coordination for at least 108 days. "That far exceeds what others have managed to do," Trimmer says.
  • It could be that the interaction of the muscles helps to maintain them.

The big picture: Artificial muscle could enable soft robots that can interact with people or be deployed to survey delicate environments (and then biodegrade when they are done).

  • One challenge though is developing soft actuators, or motors. Today's machines are driven by electric motors, gasoline engines and other technologies. Some researchers are trying to make synthetic actuators from new materials that move when heated or cooled.
  • But, "we already have what we need — it's called a muscle — we just don’t know how to put it into a robot," Trimmer says.
  • The second problem is power. Instead of lithium batteries or gasoline, some researchers are aiming to create a sustainable machine powered by sugars or fat.
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