The first time I saw the TwiddleFish, it was hanging forlornly from a thumbtack on my colleague’s corkboard. It didn’t look like much of a toy--a rubber shark about the size of a candy bar, mounted on a foot-and- half-long metal cable. I twiddled it--that is, I moved the cable back and forth between my thumb and forefinger--and it flopped like a sick shark. It needs water, said my colleague. Just like a fish. That’s the whole point.
Charles Pell, who invented the TwiddleFish, is in fact quite proud that his creation flops around like a dying fish out of water. To him, it’s a clue that he has hit on some basic mechanical truth about fish locomotion. Pell, the resident sculptor-artist-biologist at Duke University’s Bio-Design Studio, had been trying to learn how fish swim so well by building realistic models in the lab. For years he had been laboriously constructing finely detailed, anatomically accurate, hellishly complex models with wood and fiberglass for bones, rubber bands for tendons, and cable and string for ligaments, all held together with glue.
So when a colleague asked him to make a simple stationary model for an experiment on guppy mating habits, he understandably took the path of least resistance. He made a fish out of some rubber he had lying around and stuck a thin stick of bamboo into the back of its head. When he put the model guppy in a tank of water and turned it to face the real guppies-- accidentally twiddling the bamboo--he was shocked. The fish scooted forward with uncanny speed and force. I put it in the water, and sure enough, the stupid thing swam, he recalls. It was unsettling, eerie. You could see that it was swimming just like a real fish.
