Page 47 - Materials Science and Engineering An Introduction

C h a p t e r 2 Atomic Structure and

Interatomic Bonding

The photograph at the bottom of this page is of a
gecko.
Courtesy Jeffrey Karp, Robert Langer and Alex Galakatos fascinating and extraordinary animals. They have very

Geckos, harmless tropical lizards, are extremely
sticky feet (one of which is shown in the third photograph)
that cling to virtually any surface. This characteristic makes
it possible for them to run rapidly up vertical walls and
along the undersides of horizontal surfaces. In fact, a gecko
can support its body mass with a single toe! The secret to
this remarkable ability is the presence of an extremely large
number of microscopically small hairs on each of their toe
Courtesy Jeffrey Karp, Robert Langer and Alex Galakatos weak forces of attraction (i.e., van der Waals forces) are established between hair molecules and
pads. When these hairs come in contact with a surface,

molecules on the surface. The fact that these hairs are so small and so numerous explains why the
gecko grips surfaces so tightly. To release its grip, the gecko simply curls up its toes and peels the
hairs away from the surface.
Using their knowledge of this mechanism of adhesion, scientists have developed several
ultrastrong synthetic adhesives, one of which is an adhesive tape (shown in the second photo-
graph) that is an especially promising tool for use in surgical procedures as a replacement for
Paul D. Stewart/Science Source healing process. Microscopic features of this adhesive tape are shown in the top photograph.
sutures and staples to close wounds and incisions. This material retains its adhesive nature in wet
environments, is biodegradable, and does not release toxic substances as it dissolves during the

Barbara Peacock/Photodisc/Getty Images, Inc.

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