According to the Science Journal, the Stingray Project was led by researcher Sung-Jin Park based in Cambridge, MA. He says the tiny, 16-millimeter-long robots take about a week to make, mostly because of the time it takes to grow the heart muscle cells in the stingray mold. Park is a scientist in Kevin Kit Parker’s lab at Harvard University, which four years ago made a biohybrid jellyfish robot. “The jellyfish was impossible to control,” Park says, a challenge he overcame with the comparatively agile stingray.

Rays are “an ideal blueprint” for the next generation of autonomous underwater vehicles, says Keith Moored, a mechanical engineer from Lehigh University in Bethlehem, Pennsylvania. “Manta rays are very efficient swimmers,” Moored says, and “modeling their underwater gliding could provide a promising means for conserving energy.” Park’s robot is based on a different ray species, but the same principles apply.


The robotic stingrays are made in four layers on a titanium mold. A stretchy polymer layer is laser cut into the stingray shape, followed by a thin gold skeleton. This is covered with a second stretchy layer before the heart muscle cells are seeded.

When the heart muscle cells are activated, the signal to contract spreads down the cells in a line. Park aligned the cells he obtained from a rat heart in a serpentine zig-zag pattern along the fins of the stingray. This allows the fins to move in wavelike undulations as the contraction spreads from front to rear.

Of course, the robotic stingray is not a perfect replica of the real deal. The robot’s muscles can only contract downward. Actual stingrays have a second muscle layer for big upstrokes, while the robot uses the elastic energy of the gold skeleton to move its fins back in place. “That’s why we think there is a performance gap, and adding a second layer might close that gap,” Park says.

The muscles are controlled via light through a technique known as optogenetics. Here, the gene for a protein derived from algae is inserted into the muscle cells. Blue light causes this protein to activate the muscle tissue. While this sort of biobot has been made before, Park’s stingray shows greater maneuverability. Park guided the robot with LED lights through a simple obstacle course, showing that the stingray outperforms other biohybrid robots in speed, distance, and durability. Still, the stingrays are not exactly Olympic swimmers, traveling only 1.5 millimeters per second in a 250-millimeter obstacle course.

As for why anyone would want a little robotic stingray, Park says he is simply “interested in the biological model, making these circuits, and designing a signaling pathway.” Developing models for how engineered heart tissue contracts may also aid in developing future artificial organs.

Moored says that using real biological muscles can lead to “an exceptionally quiet noise signature” compared to other technologies. “This is important for a range of applications from producing stealthy reconnaissance vehicles to developing devices that can non-invasively track species and observe their behaviors,” he says.


Another robotic crustacean, a mechanical mussel, was born on the other side of Boston at Northeastern University and was devised by Dr. Brian Helmuth 18 years ago to measure the climate change conditions of the oceans. Dr. Helmuth’s shellfish contains little thermometers and data loggers to record the temperature every 10 minutes, approximating the internal temperature of the actual mussels nearby.

“The battery powered mussels, nestled in beds from Canada to Chile and from Oregon to New Zealand, provide greater insight into the thermal stresses being placed on various organisms by climate change,” Dr. Helmuth said. The data undermines the widely held theory that only animals and plants living at the edges (southern in the Northern Hemisphere, northern in the Southern Hemisphere) of a habitat will be most affected by rising temperatures, causing them to die off or migrate. Instead, species in various “hot spots,” as he calls them, are likely to be affected by a warming world, too.

Instead, Dr. Helmuth said, the temperatures that he and his team have gathered show that mussels can experience daily fluctuations of as much as 20 degrees Celsius, or about 36 degrees Fahrenheit, even at sites well within the species’ natural range. On the Oregon coast, for example, low tide, when the mussels are not covered by water, is frequently in the middle of the day, and in the summer warming midday air and water temperatures  put more stress on the mussels.

The complete set of data — temperatures taken at 10-minute intervals in more than 70 places over the last 18 years — was published last week in Scientific Data, a journal from Nature Research. It’s the first time it has all been made available, though Dr. Helmuth and others had used the information in other scientific papers.

Dr. Helmuth said that the thermometers take temperatures as the mussels experience them — the sun shining directly over the water, wind rippling the surface — to get a better idea of how these animals are reacting to a changing climate. He notes that mussels are the most reliable indicator of how the ecosystem as a whole may be doing.

Somehow the irony of biomimicry is not lost in this post, humans cause global warming and then manipulate nature to build robots to correct their mistakes…