A new stingray bot about the size of a penny relies on light-sensitive heart cells to swim. Zaps with light force the bot’s fins to flutter, letting researchers drive it through a watery obstacle course, Kit Parker of Harvard University and colleagues report in the July 8 Science.
The new work “extends the state of the art — very much so,” says bioengineer Rashid Bashir of the University of Illinois at Urbana-Champaign. “It’s the next level of sophistication for swimming devices.”
For decades, the field of robotics has been dominated by bulky, rigid machines made mostly of metal or hard plastic. But in recent years, some researchers have turned toward softer, squishier materials, such as silicones and rubbery plastics (SN: 11/1/14, p.11). And a small group of scientists have taken it one step further: combining soft materials with living cells.
So far, there’s just a handful of papers on these hybrid machines, says Bashir, whose own lab recently reported the invention of tiny, muscle-wrapped bots that inch along like worms in response to light.
In 2012, Parker’s team built a robotic jellyfish out of silicone and heart muscle cells. Electrically stimulating the cells let the jellyfish push itself through water by squeezing its body into a bell shape and then relaxing.
But, Parker says, “the jellyfish just swam.” He and his colleagues couldn’t steer it around a tank. They can, however, steer the new stingray.
He explains the team’s strategy with a story about his daughter. When she was little, Parker would point his laser pointer at the sidewalk and she’d try to stomp on the dot. He could guide her down a path as she followed the light. “She got to be independent and I got to make sure she didn’t step out into traffic.”
Parker guides his stingray bot in a similar way.
Layered on top of the bot’s body — a gold skeleton sandwiched between layers of silicone — lies a serpentine pattern of cells. The pattern is made up of about 200,000 these cells, harvested from rat hearts and then genetically engineered to contract when hit with pulses of blue light.