This Robot Fish Powers Itself With Fake Blood

This story begins thousands of feet up in the air with migratory birds, and ends with a robotic fish swimming through the water below. To prepare for their journeys, birds fatten up big time, perhaps doubling their weight, essentially turning themselves into feathered batteries. Over many days and many miles, they burn that energy reserve to power their wings and keep themselves from starving and freezing. Eventually they reach their destinations emaciated. A fine idea—thought engineers from Cornell and the University of Pennsylvania—for a new energetic system for machines. It got them thinking: fat is a cool battery, but not necessarily feasible to replicate in a robot. But blood? In a human, blood distributes oxygen and energy for cells throughout …