Thanks for the added publicity..Let's just all start talking in XML; then
our discussion can be portable cross platforms (I grew tired of just these
one line XML references).
-Chris

-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]]On
Behalf Of Wirt Atmar
Sent: Tuesday, August 27, 2002 12:51 PM
To: [log in to unmask]
Subject: [HP3000-L] OT: Sticky fingers


I thought that this was interesting enough to repeat here:

======================================

By WILLIAM McCALL
.c The Associated Press

PORTLAND, Ore. (Aug. 27) - The mystery of what makes geckos stick to just
about anything - a question that has puzzled scientific minds since
Aristotle
- finally has been solved, according to a new study.

The answer involves the geometry, not the biochemistry, of the lizard's
feet,
meaning scientists may be able to duplicate the same geometric principles to
create things such as robots that can walk on any surface in any direction,
the researchers say. Another possibility is something as simple as Band-Aids
that hold tight but don't stick when they're peeled off.

``I just saw the movie 'Spiderman' and I realized that some day we'll be
able
to do even better than he does sticking to things,'' said Kellar Autumn, a
Lewis & Clark College biologist in Portland and lead author of the study
published Tuesday in the Proceedings of the National Academy of Sciences.

Researchers found that the tips of the hairs on the bottom of gecko feet are
tiny enough to take advantage of a weak attraction between individual
molecules called van der Waals forces.

Geckos have millions of microscopic hairs on the bottoms of their feet that
are narrower than human hairs, and each splits off into 1,000 tips that are
so small they cannot be seen with a conventional microscope and can be
detected only with an electron microscope.

The shape of the hairtips also is critical, allowing the small lizard to
scamper up walls and across ceilings by sticking its toes to nearly any
smooth surface in less than one eight-thousandth of a second and unsticking
them in half that time.

``What we discovered was the angle the little shaft of the hair makes with
the surface is the critical variable,'' Autumn said.

``The gecko has this really unique way of taking its feet off the wall - it
peels its toes like tape,'' he said. ``When that angle reaches 30 degrees,
the hair pops off.''

Aristotle noted the climbing abilities of geckos in the fourth century B.C.
and scientists have been actively trying to solve the mystery for roughly
the
past century, ever since Dutch physicist Johann van der Waals won the Nobel
Prize in physics 1910 for his research on the gaseous and liquid states of
matter, Autumn said.

Earlier studies of gecko feet had reduced the explanation to either the
capillary effect of tiny amounts of water that create suction or something
that worked whether there was any water or not, in this case, the van der
Waals attraction between molecules.

Autumn and a team of researchers at the University of California at
Berkeley,
the University of California at Santa Barbara, and Stanford University
fabricated a synthetic version of the gecko hairs and tried them on two
different kinds of highly polished, extremely smooth semiconductor chip
materials.

Both chips allow van der Waals forces to work, but a silicon-based chip also
allows the capillary action of water to work while a gallium arsenide chip
prevents any effect by water.

The synthetic hairs stuck to both chips, just like real gecko feet, Autumn
said.

``I think the experimental evidence they provided is the definitive test - I
think they've really nailed it with this one,'' said Bill Kier, a University
of North Carolina at Chapel Hill biologist who studies the way octopuses
stick to surfaces.

The study also is a valuable tool for developing synthetic materials, he
said.

``Often it's not the best strategy to copy Nature piece by piece, but rather
to extract the basic principles,'' Kier said.

``And this is a lovely example.''

=======================================

Wirt Atmar

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