Harvard Engineer Unveils Robotic Stingray Powered by Rat Muscle Tissue by David Z. Morris @FortuneMagazine July 9, 2016, 1:06 PM EDT E-mail Tweet Facebook Linkedin Share icons A team of engineers have unveiled a frankly bizarre new “biohybrid” robot modeled on a stingray. The swimming robot is controlled by light cues and is constructed of a gold skeleton, two layers of silicon, and a mesh of genetically engineered rat muscles. The robot, which is about the size of a nickel, was unveiled on Friday in the journal Science. According to the researchers, the project offers a radical new option for robotics engineers, who have increasingly sought to use soft materials to mimic the complex and fine-tuned movement of animals. According to an outside roboticist speaking to Popular Mechanics, the use of rat muscle tissue was key to building the stingray robot, which would have been larger and less maneuverable if made from currently available electronics and motors. Get Data Sheet, Fortune’s technology newsletter. In addition to providing mobility, the muscles function as the robot’s control system. The muscle cells were modified using optogenetics, a recently pioneered genetic engineering method that makes cells light-sensitive. The muscles were shaped using geometric designs on the machine’s silicon superstructure. Researchers can control the robot’s movement with lights: flashing lights faster causes it to stroke faster, while shining lights on only one side causes it to turn. The robot is a project of Harvard’s Disease Biophysics Group, led by Kevin Kit Parker. Parker explained to Popular Mechanics that gold was chosen for the skeleton because it had the right attributes to provide recoil, “so that the pectoral fins bounce back to their original positions.” For more on robotics, watch our video. Parker worked on the stingray-rat-bot with a team including faculty at the University of Illinois at Urbana-Champaign, the University of Michigan, and Stanford University Medical Center. Parker’s main goal, surprisingly, isn’t to build robotic animals, or even just to creep out the general public – his work is aimed at someday engineering a biomechanical human heart (subscription link).