A team of researchers at Virginia Tech, has discovered the method ducks use to suspend water in their feathers while diving, allowing them to shake it out when surfacing. The discovery opens the door for applications in marine technology. Findings were published in the journal ACS Applied Materials & Interfaces on June 2.
Jonathan Boreyko, associate professor in mechanical engineering at Virginia Tec, got this idea when he was at Duke University. His walk took him right through the scenic Duke Gardens, passing by ponds with lots of ducks. He noticed that when a duck comes out of the water, they'd shake their feathers and water would fly off. He realized that what they were doing was a de-wetting transition, releasing water that was partially inside of their feathers. He knew this is the secret behind their successful diving.
Boreyko remained intrigued with how the balance was struck, curious about the mechanisms that allow a duck to hold water in its feathers without sinking completely. He shared that intrigue with Farzad Ahmadi, a graduate student in his lab. Ahmadi picked up the project and dove into the finer details. He examined duck feathers closely, and conducted experiments that led to some surprises.
Ahmadi found that feathers have micro-sized openings in them, tiny slots that allow pressurized water to pass through. A duck sitting on the surface of a pond isn't encountering any water pressure, so the water penetration is negligible. A duck diving downward, however, encounters a steady increase in hydrostatic pressure, something familiar to anyone taking a dive into the deep end of a pool.
He also discovered that as the number of feather layers increases, the pressure required to push water through all the layers must also increase. This establishes a kind of baseline, a maximum pressure up to which feathers hold the water entering them, but do not allow the water to reach a duck's skin.
