Sign up for the Smarter Faster newsletter A weekly newsletter featuring the biggest ideas from the smartest people Notice: JavaScript is required for this content. In 2014, researchers at the University of Illinois created a microscopic swimming robot. This accomplishment alone might not have attracted much attention. But what set it apart was how they constructed their creation: with cardiac muscle cells derived from rats. This was one of the very first “biohybrid robots.” With perceptions shaped by decades of science fiction, the general public has long viewed robots as nonbiological entities. Their bones are metal, their hearts are batteries, and their muscles are motors, pistons, and gears. They might be enveloped in real-looking synthetic skin, but this is merely a cloak for their inorganic interiors. Now, scientific advances have increasingly shown that biological beings aren’t just born; they can be built. Two years after the biohybrid swimmers, researchers at Harvard scaled up the idea to make the first biohybrid “animal” — a 16-millimeter-long ray. With a body of elastomer, a skeleton of gold, and …