It looks like Harvard's octopus robot is going to have some stiff competition. Chinese researchers have crafted a soft manta ray-inspired bot that could surveil the seas without harming nature in the process. Rather than rely on stiff metal or plastic for its body, the artificial swimmer is made out of a combination of flexible polymer (for its muscles) and silicone (for most everything else) that shouldn't damage sea life. And importantly, there's no motor -- the ray gets around using a lithium battery whose cyclic voltage causes the muscles to bend, flapping fins in the process. Electromagnets help steer the tail.