8

Chitinous Membranes and Analogous Material

111

The wet samples of chitin have higher strength and toughness as compared to dry

samples.

Apart from all the above-known applications, chitin can also be used for making a

streamlined body of fliers. The thin membranous flexible wings can also be designed

from chitin. These wings can be attached to the body by using available commercial

resilin depending on the frequency characteristics and power available of the system

under design.

Applications of chitin depend on account of its bio-degradability, non-toxicity,

physiologically being neutral, antibacterial, gel-forming affinities and affinity for

proteins.

Analogous Materials

Resilin

Resilin is an elastomeric protein found in insects, in the tendons and at the wing

hinges. Thus, it helps insects for jumping and to move their wings efficiently. Resilin

and chitinous cuticles together form a composite structure for energy storage needed

in the jumping of hoppers (insects). The catapult mechanism of rubber-like protein

as an elastomere is a notable feature. Resilin was discovered by Torkel [16] from

locust wing hinges as a rubber-like cuticle. Later, resilin was also found in the salivary

glands of assassin bug and in the feed organs of these insects. It has also been reported

in the case of Cicada and also in soapnut bugs, which have resilin in their sound-

producing tymbals. A resilin-chitinous cuticle also would prevent structural failures

and contribute to improved fatigue. Recently, resilin has been reported in flapping

wing membranous as in small patches.

Resilin plays a vital role in insect hinges and also for jumping action in small

insects. It stores energy for achieving jumping locomotion. The storage capacity for

resilin is 10⁶ w/kg and for direct muscle contraction is about 250 W/kg [10].

Considering the resilin to be loaded in pure compression, elastic potential energy

Ue stored is given by

Energy (Ue) = ^{E A}

2L ^δL2

(8.1)

where

E

is Young’s modulus for resilin.

A

is cross-sectional area of resilin part.

L

is resting length of resilin part on the load.

δ L

is the change in length of resilin under full compression at the time of the

jump.