When you think of a cyborg, you think of an animal with robot enhancements. A mechanical arm, perhaps, or a bionic eye. But what about the reverse—a robot enhanced with animal parts? That's how this robot stingray was made. It's a bio-robot made out of rat heart muscles.
The tiny ray-like robot is just an inch long and is activated and guided by shining a light onto it. Thanks to the 200,000 genetically-engineered rat heart-muscle cells that line the bottom layer, it can propel itself through water with the same flapping, undulating motion used by real rays, something that would be impossible at this size using regular man-made propulsion mechanisms.
The robo-ray was built by Harvard bio engineer Kit Parker and is made up of four layers. The top layer is silicone, the same as you'd find in a breast implant. This layer, cast from a titanium mold, gives structure for the rest of the robot. Next is a gold skeleton, chosen because it has the right amount of flex, and it's easy to work with. "The skeleton's there because we needed some recoil," Parker told Popular Mechanics, "so that the pectoral fins bounce back to their original positions."
Next up is a membrane of more silicone. This forms a barrier between the gold and the next layer, the rat cells. These grow across the underside of the robot, spreading into a pattern cast into the silicone.
The heart muscles are genetically-engineered to contract when hit by light of a specific wavelength, and as each one contracts it sends a signal to the next, causing a ripple like movement which causes the entire body to undulate, swimming like a real ray. It can even be steered by shining a brighter light on one side. The robot lives in a nutrient bath which keeps it alive, and after six weeks of swimming, 80 percent of its cells were still alive and well. But because the ray-bot has no immune system, it would die pretty quickly as soon as it got outside the lab.
A robotic fish made of rat cells is pretty awesome, but the technology is useful, too. It could inform researchers who are trying to grow human heart cells, for example. It is also interesting from an ethical and philosophical point of view. Is a device powered and guided by living tissue alive? "I think we've got a biological life-form here," Parker told Popular Mechanics. "A machine, but a biological life form. I wouldn't call it an organism, because it can't reproduce, but it certainly is alive."