One afternoon, John W.M. Bush, MIT math guru, ventured to a pond to collect insects known as water striders for his research. It wasn’t until he returned to his lab that he discovered an interloper in his bucket.
“I accidentally caught a backswimmer while I was lunging for a water strider,” recalled the associate professor of mathematics at the Massachusetts Institute of Technology.
An insect capable of diving into water and staying there indefinitely, the backswimmer has long befuddled scientists. So Bush set out to solve the mystery of how backswimmers do what they do.
It turns out they breathe underwater using the same mechanism that lets water striders skitter on top: water-repellant hairs that create a cushion between insect and water. The backswimmer traps a thin layer of air between its body and the hairs, creating an external lung that keeps its breathing holes from getting wet.
Oxygen from the surrounding water diffuses into the air bubble, replenishing the insect’s supply.
Earlier this month in the Journal of Fluid Mechanics, Bush described how the bubbles remain intact even as the insects dive deeper and water pressure increases. Pollution, though, can change the wetting properties of the hairs, affecting their ability to trap air.
Humans won’t be exploring the depths this way anytime soon. Still, Duke University biologist Steven Vogel said that with engineers and biologists collaborating more and more, potential applications are nearly limitless.
“Engineers and biologists are both dealing with complex systems,” said Vogel, who was not involved in the study. “We’re really talking about the engineering of life.”
Bush envisions small underwater vehicles, powered by motors fueled by oxygen supplied by such a bubble. “This is a means by which these animals are getting power,” he said.