materials science

1. SPIDER SILK
PRESENTED BY
PINTU MAITY
M.Sc 2ND SEM
DEPARTMENT OF MATERIALS SCIENCE
Roll No.-12

2. Spider silk is a protein fiber spun
by spiders. Spiders use their silk to
make webs or other structure
which functions as sticky nets to
catch other animals, or as nests or
cocoons to protection their
offspring. They can also
suspended themselves using their
silk.
DEFINiTION

3. COMPOSITION OF SPIDER SILK
The dragline silk of the Golden Orb-
Weaving spider is the most studied in
scientific research. Spider silk is a
natural polypeptide, polymeric protein and
is in the scleroprotein group such as
collagen (in ligaments) and keratin (nails
and hair). These are all proteins which
provide structure.

4. The protein in dragline silk is fibroin which is a
combination of the proteins spidroin-1 and spidroin-2. The
exact composition of these proteins depends on factors
including species and diet. Fibroin consists of
approximately 42% glycine and 25% alanine as the major
amino acids.
A female specimen of Argiope bruennichi
wraps her prey in silk.
A garden spider spinning its web

5. TYPES OF SPIDER SILK
 There are seven types of silk produced by
seven silk glands. A single spider does not
possess all seven glands but has at least
three if it is male (dragline, attachment and
swathing silk) or four if it is female. The
additional one is for egg sac silk.



6. •Achniform gland: swathing silk.
•Cylindriform gland: egg sac silk.
•Ampullate glands (major and minor): non-
sticky dragline silk. Silk from the minor ampullate gland is only half as
strong as that from the major gland.
•Pyriform gland: attaching threads - attachment discs are
made which anchor a thread to a surface or another thread.
•Flagelliform gland: core fibers of sticky silk.
•Aggregate gland: outer part of sticky silk - droplets of an
adhesive substance are deposited along the threads.

8. The glands are located on the lower side of the
abdomen (see diagram below) and contain a
watery fluid known as 'dope'. This fluid passes
through to the spinneret via a multitude of
microscopic tubes where water recovery and
solidification begins. Fluid from different glands
can lead to the same spinneret so silk with specific
properties required for a particular function can be
produced. There are usually three pairs of
spinnerets but this can vary between 1 and 4 pairs
depending on the species. The substance exits
through the spigots which are mobile, finger-like
protrusions and the resulting silk emerges as a
solid. There are many spigots so many fibres are
bound together like a cable. The diameter of a
single fibre is controlled by the muscular action of a
valve. The faster and tighter the strand is drawn,
.
HOW DO SPIDER PRODUCE SILK?

10. HOW do COLLECT THE SILK FROM SPIDER ?
Using the silk extraction machine , we collect
the spider silk .
However the production of spider silk is not simple and there
are inherent problems. Firstly, spiders cannot be farmed like
silkworms since they are cannibals and will simply eat each
other if in close proximity. The silk produced is so fine that
400 spiders would be needed to produce only one square
yard of cloth. The silk also hardens when exposed to air
which makes it difficult to work with.

11. So, Biological Scientists , they are discovered
a alternative approach. More recently, Nexia
Biotechnologies Inc in Montreal, Canada have
inserted silk genes into goats to produce silk
proteins in their milk. This is hoped to be a
better method because protein from bacteria is
not as strong due to faulty cross-linking of the
proteins and hard white lumps can form. Milk
production in mammary glands is similar to silk
protein production in spiders so it is thought
that proper protein cross-linking could occur in
goats.
A MODERN APPROCH

12. MALE
FEMAL
E

13. Most silks, in particular dragline silk, have
exceptional mechanical properties. They
exhibit a unique combination of
high tensile strength and extensibility
(ductility). This enables a silk fibre to
absorb a lot of energy before breaking
(toughness, the area under a stress-strain
curve).
MECHANICAL PROPERTIES

14. Strength:
In detail a dragline silk's tensile strength is comparable to that
of high-grade alloy steel (450 - 2000 MPa) and about half as
strong as aramid filaments, such as Kevlar (3000 Mpa).
Energy density
The energy density of dragline spider silk is roughly
1.2x108J/m3.
Extensibility
Silks are also extremely ductile, able to stretch up to five times
to their relaxed length without breaking.
Spider silk is able to keep its strength below -40°C. The
toughest silk is the dragline silk from the Golden Orb-
Weaving spider (Nephilia clavipes).
THERmal poperties

15. Toughness
The combination of strength and ductility gives dragline
silks a very high toughness (or work to fracture).
Supercontraction
When exposed to water, dragline silks undergo
supercontraction, shrinking up to 50% in length and
behaving like a weak rubber under tension.

16. Kevlar VS. Spider dragline silk

17. Artificial Tendon/Ligament: Biocompatibility of spider silk, and the unusual
characteristics of the stiffness/stretchiness combination has scientists
considering its use for tendon and ligament repair in humans. Candidates for a
tendon/ligament replacement must meet the requirements of strength to
withstand regular impact and pressure, as well as avoiding fatigue during
regular use.
Malfunctioning of parachute straps: The use of the silk’s tensile strength
could be incorporated in parachute straps, to deter the chances of
malfunctioning straps, and increase safety.
Recreational and Industrial uses: For recreational and industrial uses,
biodegradable fishing lines composed of spider silk would resist snapping
under the force of a large biting fish. Also it’s potential use in instrument fibres
for violins and cellos.
Idea of body armor: The idea of body armor woven from dragline silk, has
been hypothetically observed. In the biological environment, 70% of the kinetic
energy from a prey flying into a spider’s web is absorbed as heat and
dissipated. With this background information, it can be conveyed that with the
use of engineered spider silk the shock a person would feel from a bullet could
USES OF SPIDER SILK

18. FUTURE STEPS
 In the future, the scientists plan to
incorporate the silk genes into alfalfa plants,
which they say could produce even larger
quantities of silk. They explain that not only is
alfalfa widely distributed, it also has a high
(20-25%) protein content, making it an ideal
crop to produce silk protein.

19. REFERENCES
• https://phys.org/news/2010-05-scientists-
goats-spider-silk.html#jCp
• https://spider-silk.wikispaces.com

20. THANK YOU