"We just can't do things the way biological systems can," Goldfarb says. "Animals do things in a totally different way [than machines]. There is no machine that has the maneuverability of a hummingbird. At the same time, there are some things that man-made systems can do better. There is no animal that can fly as high or as fast as a 747.

"Biology and man-made systems are at opposite ends of the spectrum. That is one reason prosthetics are such a challenge. Functionally, we can try to provide the same function as an arm, but we have to do it in a very different way. From the outside, the arms might look the same, but from the inside - the fundamental way in which they operate - they are going to be very different. I, and I think a lot of engineers, would love to be able to develop things very close to a biomimetic route, but our work is just fundamentally different,"