Researchers at Harvard University have built a light-sensitive, self-propelled artificial machine-organism, in the form of a tiny robot stingray. The project was done in an effort to test the feasibility of making hybrid replacement organs for human patients, such as bioartificial hearts, that could use natural muscle motions to function, as opposed to the electrical operation that today’s prosthetics require.

This hybrid mechanism-organism was constructed around a 3D-printed skeleton made of gold, utilizing the metal for its elastic properties, with a body formed around the skeleton made from two layers of a silicone substrate. In between the silicone layers was a pattern of genetically-altered cardiac cells from a rat, laid down using a 3D printer, to provide the muscle for the device. The heart cells were genetically engineered so that they would contract when exposed to light, and were arranged in a pattern so that collectively their contraction would form a pulse that moved from the front of the robot toward the back, to emulate the wave pattern that natural stingrays use to propel themselves through the water.

The result was a small aquatic robot that propels itself through the nutrient solution it is kept in. The researchers could activate the device by exposing it to blue light, and can even steer it, as the cardiac cells on each side of the device were set up to react to different wavelengths of light.

While the simulated stingray can only move about 9 meters (30 feet) per hour, the researchers were able to fine-tune the device so that they could direct it through a tiny obstacle course set up in it’s tank. It is also limited to existing in its nutrient solution, otherwise the cardiac cells that propel it would starve and die. However, the researchers are hopeful that their efforts will pave the way for future medical advancements. As neural engineer Kedi Xu, at China’s Zhejiang University, explains: “One can imagine that one day we can use this technology to rebuild parts of the human body.”