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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Geckos' Sticky Secret Revealed
8 June 2000 6:00 pm
The Tokay gecko is the envy of every serious rock climber and Spiderman wannabe. This tropical lizard runs up walls and upside down across ceilings as readily as across floors. It can hang from one toe pad--that's akin to holding oneself in midair by a fingertip. The gecko's secret, says Kellar Autumn, a biomechanist at Lewis and Clark College in Portland, Oregon, is that each toe pad has rows of tiny hairs with multiple split ends.
The hairy feet by themselves aren't news. The soles of gecko toe pads are famous for being covered with rows of hairs, called setae. Each seta's curved shaft ends in many hundreds of stubby tendrils--too small to see with a regular microscope--with rounded ends. To figure out how these hairs might help geckos hang upside down, Autumn--then at the University of California, Berkeley--and his colleagues used a microelectrical mechanical sensor to measure the lateral and perpendicular forces exerted by a single hair that had been removed from a gecko's foot.
At first the hair didn't stick well to the sensor surface. But that changed after the researchers gently pressed the hair into the surface and then began to drag it across and nearly parallel to the sensor--movements that resemble how intact setae work as the gecko puts its foot down.
Previously, researchers had measured the overall adhesive forces of a gecko foot and calculated the contributions of individual hairs. But amazingly, the new study shows that "each [hair] was 10 times more adhesive than we would have predicted," Autumn says. One seta is strong enough to hold up an ant, and a million could support a small child. Autumn and other researchers have ruled out suction, glue, or even electrostatic forces; instead, they think that as the tendrils get close enough to the surface, they generate weak intermolecular forces, akin to van der Waals forces, that add up to a secure foothold.
The work has delighted other scientists. "It's great to look at how evolution has solved mechanical problems," marvels Bruce Jayne, a functional morphologist at the University of Cincinnati. The researchers hope that further studies will help them design simplified setae that can be manufactured. Eventually, Full and Autumn envision an all-purpose, reusable, gecko tape--one that leaves no residue behind.