When Is a Robot Not Mechanical? When It's an Android

The standard definition of a robot is an electromechanical device that works automatically. But an artificial jellyfish created by Harvard and Caltech researchers goes a lot further than biomimicry using electromechanical means. It's more like an android: It looks like a real creature, moves like one, and incorporates living cardiac muscle cells.

The artificial jellyfish, dubbed "Medusoid," has cultured rat heart muscle cells that produce the pumping action that propels the artificial creature's silicone muscle structure through water.

"As engineers, we are very comfortable with building things out of steel, copper, concrete," said co-researcher Kevin Kit Parker, professor of bioengineering and applied physics at Harvard's School of Engineering and Applied Sciences, in a Harvard Gazette article describing the project. "I think of cells as another kind of building substrate, but we need rigorous quantitative design specs to move tissue engineering to a reproducible type of engineering."

Although this graceful, squishy, robot jellyfish's movements aren't nearly as elegant as those of Festo's AirJelly, they make the action of the silicone robot we reported on that mimics its surrounding look crude in comparison.

Parker, an authority on cell- and tissue-powered actuators, collaborated with Janna Nawroth, a Caltech doctoral student in biology, to reverse engineer the movements of a natural Medusa jellyfish. Nawroth's adviser, John Dabiri, a professor of aeronautics and bioengineering at Caltech, was consulted for his expertise in biological propulsion. The researchers published their work in an article in Nature Biotechnology (subscription or payment required).

The researchers say that a major goal of creating Medusoid was to advance biological tissue engineering. To date, many of these efforts have focused on copying a tissue or organ without considering the relationship between the components and their function, or analyzing which materials would best suit that function.

Since jellyfish use their muscles to pump their way through the water, and their basic structure is similar to that of a beating human heart, the researchers decided to reverse-engineer that function to advance heart tissue research.

After mapping the alignment of subcellular protein networks in the Medusa jellyfish's muscle cells, they studied the propulsion system's electrophysiological triggering and the propulsive stroke's biomechanics. The team found that a sheet of cultured rat heart muscle tissue contracted when electrically stimulated in liquid. They used a silicone polymer to make the artificial Medusoid's body, a thin membrane with eight armlike appendages, and matched the subcellular, cellular, and supracellular jellyfish muscle architecture with the rat heart muscle cells. When the researchers placed Medusoid in a container of salt water and shocked it, the device began swimming with synchronized muscle contractions.

Is it an android? Maybe not quite yet. The researchers' next steps will include incorporating simple intelligence so the artificial jellyfish can respond to its environment with more advanced behaviors, such as moving toward a light source, and modifying it so it can move in a particular direction.

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