Few creatures are more frightening
than sharks, but these complex fish
have also provided inspiration for several
useful technologies.

Throughout history, shark skin has
been used by many cultures, as sandpaper,
non-skid shoes, and the like. Swimsuits modeled on shark
skin are claimed to reduce drag by up to 4 percent. Now, synthetic
shark skin could make ships and submarines faster and
less expensive to operate.

The growth of barnacles, mussels, and algae increases drag by up
to 15 percent, and adds to fuel costs for commercial shipping
and the military.

Paints laced with copper curb the problem, but must be reapplied
periodically to be effective. They are expensive, and toxic
to other marine life. Fish, crabs, and whales are fouled by hitchhiking
marine life, but rarely sharks. Scientists have discovered
that part of the secret is in the complex design of their scales.

Shark scales are made of a hard material called dentin. Like tiny
teeth that all point backward, they make a shark feels smooth
from head to tail, but rough the other way. The scales flex individually,
limiting the amount of exposed surface area on which
organisms can attach. They also create tiny vortices that reduce
drag, making the shark faster and more energy efficient.

Barnacles make some of the strongest adhesives known, but the
glue can only penetrate so far into a rough surface, explaining
why scales can prevent them from sticking.

With the fake shark skin applied, a ship moving at 4-10 knots becomes
self-cleaning, leaving most fouling organisms in its wake.