February 3, 2010

Water Adhesive Technology Offers Potential Superhero Abilities

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Cornell researchers have created a technology that one day could allow humans to walk on walls –– without any radioactive spider bites. The palm-sized device uses the combined surface tension of a series of minute water droplets to create a strong adhesive force. Funded by the Defense Advanced Research Projects Agency and the National Science Foundation, the device may one day be used as more than just a recreational accessory. It could allow soldiers to scale walls with ease and give them a tactical advantage.

The key to the invention lies in the controllability of its rapid adhesion, which allows the device not only to stick to surfaces, but to unstick just as easily. Unlike previous attempts at gecko-like adhesion mechanisms, the device can cling to almost any surface, regardless of its coarseness.

“This is a little device that can grab and release walls and objects,” Prof. Paul Steen, chemical and biomolecular engineering, said.

Steen, who pioneered the project with his former post-doctorate student Michael Vogel, was inspired by the Florida leaf beetle’s ability to adhere to surfaces and withstand force up to 100 times its own weight. He learned about the beetle in an afternoon talk at Statler Hall.

After five years of research and development, Steen and Vogel have a tangible result that replicates the leaf beetle’s extraordinary adhesive force.

The device uses a metal plate with a grid of tiny holes, micrometers in diameter. Beneath the plate lies a liquid reservoir, from which water is pumped by an electric field created with a standard 9-volt battery.

The surface tension from these exposed droplets causes the plate to stick to other surfaces, like how a glass of ice water condenses and suctions to a table when lifted. When the electric current is reversed, the water droplets are sucked in from the plate and the adhesion between the surfaces releases.

“The device pushes out small droplets of water and these droplets attach to whatever substrate you’re trying to attach to,” Vogel explained.

The smaller the holes, the more droplets and the greater the adhesive force. According to Vogel, a one-square-inch plate covered in millions of 1-micron sized holes could support up to 15 pounds.

The device could be adapted to other liquids with different properties, like oil, with varied effects that have yet been explored, Steen explained.

Yet, both researchers have their eyes set on the new invention’s vast potential.

“The real question is, how strong can we make the device?” Vogel stated.

If the scientists were able to create a 3-by-5 inch plate and fit it to a shoe sole, for example, it could support up to 225 pounds.

The concept and its applications already have science blogs buzzing.

“Once the researchers master the pump mechanism to make adhesive forces even stronger, they want to turn humans into Spider-Man,” Katie Drummond wrote on wired.com.

While a Spider-Man type device is one of the gadget’s “wilder” applications, the invention’s enormous surface tension has potential uses as a small-scale explosive device with significant power, Vogel stated.

“You can think about making a credit card-sized device that you can put in a rock fissure or a door, and break it open with very little voltage,” Steen told the University. “It’s a fun thing to think about.”

Original Author: Dani Neuharth-Keusch