Biomedical Engineering Reference
In-Depth Information
the leg of the seal and to a lesser extent that of the frog. This similarity to the latter led to the naming
of divers — frogmen, which is clearly a biomimetically inspired name.
1.5.4 Defense and Attack Mechanisms in Biology
A critical aspect of the survival of various species is having effective defense and attack mechan-
isms to protect against predators, catch prey, secure mating, protect the younger generation, procure
and protect food, and other elements that are essential to survival. The following are some of the
biologically inspired mechanisms that were adapted by humans. Further details are discussed more
extensively in Chapter 13.
1.5.4.1 Camouflage
The chameleon and the octopus are well known for their capability of changing their body color. The
octopus matches the shape and texture of its surroundings as well as releases ink to completelymask its
location and activity — and yet, the octopus is a color-blind creature (Hanlon et al., 1999). Another
aspect of the octopus' behavior is its ability to configure its body to allow traveling through narrow
openings and passages. These include tubes, which are significantly smaller than its normal body cross-
section. Generally, camouflage is not used solely for concealment alone, it also allows the predator
to get close to its prey before charging ahead and capturing it by gaining the element of surprise while
minimizing the response time of the prey. In some creatures, camouflage provides deterrence. For
instance, some snakes, which are harmless, clone the appearance of highly poisonous snakes. Further,
some harmless flies camouflage themselves with bright colors, pretending that they are wasps.
Minutes after birth, a baby deer is already capable of recognizing danger and taking action of
passive self-defense. Since oftentimes the baby deer is left alone after birth, while the mother goes
off to search for food, the baby has to rely on its ability to hide. It does this by finding shelter and
taking advantage of basic camouflage rules. Without training, it is able to recognize which animals
pose a threat to its life. Furthermore, the baby deer is equipped with the basic skill of taking
advantage of objects in its terrain (e.g., plants), to reduce its body profile by ducking low, and to use
a surrounding background that matches its colors in order to minimize its visibility. These skills,
which are innate in the baby deer, are taught in human military training as camouflage methods.
While it is impossible for humans to imitate the octopus' ability to squeeze its body through narrow
openings (since we have bones and the octopus does not), its camouflage capabilities have been the
subject of imitation by all armies. InWorldWar II, the zoologist HughCott (1938) was instrumental in
guiding the British army in developing camouflage techniques. Modern military uniforms and
weapons are all colored in a way that makes them minimally visible by matching the background
colors in the areawhere the personnel operate. Further, like the use of the ink by the octopus, soldiers in
the army and on large naval vessels at sea use a smoke screen when they do not want to be seen. Until
recently, camouflage has been used in the formof fixed colors for uniforms, armor and variousmilitary
vehicles. With advancement in technology, the possibility of using paint that changes color is
becoming increasingly feasible, and the use of liquid crystal color displays as a form of external
coating are under consideration for active camouflage. Recent efforts are producing colors that can be
changed to adapt to the local terrain (http://www.csmonitor.com/2004/0108/p14s01-stct.htm).
1.5.4.2 Body Armor
The shell is another means of protection that some creatures are equipped with, both on Earth and
under water, and to a certain extent also in some flying insects. Creatures with body armor include
the turtle, snail, and various shelled marine creatures (e.g., mussel, etc.). There are several forms of
shells ranging from shelter that is carried on the back (e.g., snails) to those with full body cover in
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