From: matus [matus@snet.net]
Sent: Tuesday, September 17, 2002 12:14 AM
To: matus@snet.net
Subject: MFD List - Sticky gecko toes have little hairs to thank

(This is a fascinating article I came across recently.  Most animals that
stick to surfaces do so using small hooks or claws, a few wet the ends of
their feet and use the molecular adhesive forces of water to stick to
surfaces.  Yet a small class of creatures uses an  entirely different
effect, on shinning example is the Gecko.  Geckos can stick to surfaces that
are smooth and dry, or underwater or in a vacuum.  This article relates the
mechanism by which geckos, and evolution, achieves this amazing feat.  Of
note "One seta can lift the weight of an ant. A million setae, which could
easily fit onto the area of a dime, could lift a 45-pound child and a gecko
using all of its setae at the same time could support 280 pounds, the
researchers said"  Fascinating.  So where are the spiderman gloves?? - Mike)

Sticky gecko toes have little hairs to thank
August 27, 2002 Posted: 9:47 AM EDT (1347 GMT)

http://www.cnn.com/2002/TECH/science/08/26/science.geckos.reut/index.html

A gecko's sticky feet hold it suspended upside-down on a sheet of glass.


WASHINGTON (Reuters) -- Tiny little hairs and not any kind of chemical glue
help a gecko race up and down vertical surfaces as smooth as glass,
researchers reported Monday.

The finding could help scientists invent better adhesives that will work
virtually anywhere, the researchers at Lewis and Clark College in Portland,
Oregon, the University of California and Stanford University said.

"We have solved a centuries-old mystery of what makes a gecko's toes so
sticky," Lewis and Clark's Kellar Autumn, a biologist, said in telephone
interview.

Geckos and their ability to climb and hang virtually everywhere are hardly
unknown to science, but biologists had not really understood how they did
it.

At first it was assumed they had glue on their toes, but close examination
with electron microscopes shows they have millions of tiny hairs called
setae.

A seta is only about 100 micrometers long -- about the width of two human
hairs. Each seta ends with 1,000 even tinier pads at the tip.

One seta can lift the weight of an ant. A million setae, which could easily
fit onto the area of a dime, could lift a 45-pound child and a gecko using
all of its setae at the same time could support 280 pounds, the researchers
said.

Molecular attraction
The tiny pads work through a molecular attraction called van der Waal's
forces. "We confirmed it's geometry, not surface chemistry, that enables a
gecko to support its entire body with a single toe," Autumn, who studies
biomechanics, said.


Microscopic hairs help geckos climb walls.
Van der Waal's force keeps molecules together.

This is good news for Autumn's colleagues, who are trying to invent better
adhesives. "It would have been a lot more difficult if there been a
particular biochemistry that we had to duplicate," Autumn said.

If they can make hairs small enough, they should be just as strong and
sticky.

He does not think even a sandy, silty surface would thwart a hairy-footed
robot. "Geckos live all over the world, even in places where it is sandy,
and their feet don't get dirty," Autumn said. "We believe the adhesive is
self-cleaning."

Most animals and insects with sticky feet need to use water, which employs
the capillary effects to get an adhesive bond. Geckos, some other lizards
and one kind of beetle are virtually unique in their ability to attain dry
stickiness, Autumn said.

The team has started making synthetic gecko foot-hair tips that stick like
the real thing, and want to expand their output.

Could a glove equipped with similar tiny hairs help a person cling to a wall
like Spider-Man, the cartoon and film character? "I watched 'Spider-Man' on
an airplane and I couldn't help thinking we could do better than that
someday," Autumn said.

"A personal dream of mine is to see a small-legged robot with adhesive feet
walk on the surface of Mars."

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