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Watery Gecko Grip Could Lead to Stickier Tape

By Gregory Stephens,2014-07-08 12:42
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Watery Gecko Grip Could Lead to Stickier Tape

Watery Gecko Grip Could Lead to Stickier Tape

Scientists have long known that geckos can scurry up walls, Spider-Man style.

    But less well understood is how these reptiles cling to wet surfaces, which are common in their rainy tropical habitats. The answer, a new study reveals, is that a gecko's sticky toes enable the animal to walk across wet surfaces that don't get uniformly

    wet, like waxy leavesbut not on easily wettable surfaces, like glass.

    This is "an interesting question that the field of gecko biology hasn't quite looked at before" now, said study leader Alyssa Stark, a

    biologist at the University of Akron in Ohio.

    Why does it matter? Because figuring out a gecko's grip could help people make adhesives that will work in water, Stark said.

    Imagine, for instance, putting a Band-Aid on underwater and having it stick just as well as it would on land. Sticky Situation

    To examine a gecko's cling, Stark and colleagues put harnesses on six tokay geckos (Gekko gecko) and put them on four surfaces

    which varied in their wettability, or their degree of water resistance.

    The reptiles' feet were submerged in water on glass, plexiglass, a transparent plastic often used as a glass alternative, and Teflon.

Plexiglass and the transparent plastic "mimic the surface chemistry of the leaves geckos are really walking on in their natural

    environments," Stark said.

    As a gecko moved across each surface, the team applied a force in the opposite direction until the animal slipped, which allowed

    them to measure the animal's grip.

    The results showed that on glass, a film of water developed between the geckos' toes and the surface, reducing their ability to stick

    to the glass. But on plexiglass and the plastic, the geckos' toes create air pockets that allows their feet to stay drypreserving the

    stickiness.

    These results are similar "to the contact made by a terrestrial beetle underwater, where trapped air bubbles actually allow dry

    contact to occur on [water-resistant] surfaces," according to the study, published this week in Proceedings of the National Academy of Sciences.

    A "very obvious application," Stark said, would be to use this data to make a synthetic tape that can stick to wet surfaces.

    Stark suspects that the geckos' toepads evolved to negotiate wet rain forests. (Read about a new species: the strikingly striped bumblebee gecko.)

    For instance, if a gecko is caught in a tree during a sudden rainstorm, its surroundings likely won't dry for a long whilewhich means

    the reptile has to be able to cling to wet leaves in order to escape predators or find food. Airborne Fecal Matter

    Because they don't usually run away, tokay geckos have become the lab gecko of choice, Stark added. But working with the

    14-inch-long (35-centimeter-long) critters isn't easy: They don't like to be handled, and can be quite aggressive. (Watch a video of

    gregarious geckos.)

    "Part of their defense mechanism is to basically shoot fecal matter at you," she said with a laugh. It's "pretty high velocityI've

    definitely gotten nailed during experiments."

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