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Robotic fish has all the right moves

Researchers at Northwestern University have created a robotic fish that can move from swimming forward and backward to swimming vertically almost instantaneously.

Researchers have built a robotic fish that has all the right moves — it can go forward and backward, like other underwater robots, and shoot up vertically almost instantaneously.

The technology could pave the way for nimbler robots that perform recovery operations and long-term monitoring of coral reefs.

The robot is modeled after black ghost knifefish, denizens of rivers in the Amazon basin that emit a weak electric field as they hunt for prey in the dark of night. The field gives them sense in all directions.


"In order to use the fact that they can sense in all directions, they are able to move in all directions. So they have both omnidirectional sensing and omnidirectional movement," Malcolm MacIver, a biomedical and mechanical engineer at Northwestern University, explains in a video on the robo-fish.

How they move
The fish send waves up and down a ribbonlike fin on the underside of their bodies to move forward and backward. When studying the fish in a lab, MacIver and colleagues found that the fish can also suddenly shoot vertically. To accomplish the vertical motion, the fish send two waves along its underbelly fin — one from head to tail, the other from tail to head. The waves collide and stop at the center.

The team then created a computer model to figure out what happens next: The fluid motion generated by the colliding waves is funneled into a downward jet from the center of the fin, which pushes the body up.

"It's interesting because you're getting forces coming off the animal in a completely unexpected direction that allows it to do acrobatics that, given its lifestyle of hunting and maneuvering among tree roots, makes a huge amount of sense," MacIver said in a news release.

His team worked with Kinea Design to build a robot modeled after the fish. The robot — called Ghostbot — has 32 motors that give independent control to 32 artificial fin rays on the Lycra-covered artificial fin.

Tests at in George Lauder's lab at Harvard University showed that the robot moved as predicted by the computer model. "It worked perfectly the first time," MacIver said. "We high-fived. We had the robot in the real world being pushed by real forces."

Next step
The next step is to integrate an electrosensory system that is designed to work akin to the fish's, so that the robot can autonomously use sensory signals to detect an object, and then use its mechanical abilities to go near it. That sounds like something that could spark the interest of DARPA.

MacIver has his eyes on other applications.

"In the BP oil disaster, we saw that the ROVs were so difficult to maneuver that they sometimes slammed into the oil wellhead and delayed the capping operations for some weeks at a time," he noted in the video. "With our system, we are recovering much of the agility of these animals in their native habitat, which is many orders of magnitude better than current technology, and so we are really excited about pushing this forward in to the field for applications to problems such as those."

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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).