This Robot is Both Animal and Machine

Kevin Kit Parker, Sung-Jin Park, and their team of scientists have built a real-life cyborg, a robot consisting of both artificial and biological components. While not yet Terminator level, it’s both fascinating and scary. The medusoid has a body made of silicone, with a gold skeleton, covered with genetically-engineered rat heart cells that provide its movement.

(YouTube link)

The process is explained further at Science.

Infected with a virus that delivers the gene encoding the optogenetic molecular switch, the modified cardiac cells twitch  when blue light shines on them. But translating that effect into coherent motion took months of tweaking; simply getting a robot ray to move forward when light stimulated the front of its fin took Park 200 tries. Ultimately, he built 100 more robots and showed they could navigate underwater obstacle courses. To negotiate turns, Park guides a ray with two light sources, one pointed at each fin. Changing the frequency of the light slows or speeds up the contraction rate; by making one side beat faster than the other, he steers the robot left or right.

See another video at Popular Mechanics.