David Tenny

1
Properties of Spider Silk

• David Tenny
• AE 510 Manufacturing and Materials

2
Silk Glands

• 1) Flagelliform Gland
• 2) Aggregate Gland
• 3) Cylindrical Gland
• 4)Minor Ampullate
• 5) Produces the outer silk for egg sacks
• 6) Piriform Gland
• 7) Major Ampullate
• 8) Anciform Gland
• 9) Auxiliary spiral.

Silk Glands (Ref. 1)
3
Silk Excretion
When the silk proteins reach the spinnerets the
silk proteins have hardened from their previous
liquid form. The crystalline structure of the
proteins have aligned themselves to create the
silk structure. The final product is a strong
flexible protein stand spun at ambient
temperature and pressure from a small yet
intricate system of glands.
Spinnerets excreting silk (Ref. 1)
4
Chemical Composition of Silk

• Composed of Fibrion and Sericin which are similar
  proteins.
• Each protein has three regions
• Amorphous region
• Semi-solid crystalline region
• Solid crystalline region
• Fibrion and Sericin are 42 glycine and 25
  alanine
• Glycine and alanine are the smallest amino acids
• Smaller structure allows for tighter packing of
  the amino acids
• Alanine has highly aligned crystals and less
  aligned crystals
• Alanine forms chains
• Crystalline chains of Alanine connect rigid
  crystalline and amorphous remainder of protein
  forming a strong and elastic structure

View of Alanine Arrangement (Ref. 2)
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Structure of Silk

• Silks composition and structure varies between
  species and function of silk
• Applications of silk
• Egg sack
• Lasso
• Large web
• Funnel web
• Ensnaring prey
• Flight Stringer

Applications of Spider silk such as a nest or an
egg sack. (Ref. 1)
6
Version of Non-Sticky Silk

• Low magnification picture gives a single strand
  appearance
• Under higher magnification tangled strands can be
  seen
• Small strands give non-sticky silk a sticky
  quality due to fibers tangling with objects that
  it comes in contact with.
• Slack in strands permits the composite to
  elongate before they become pulled tight

Top Magnification of Spider silk (200x) Bottom
Magnification of Spider silk (1000x) (Ref. 1)
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Version of Dragline Silk

• Bundled structure of threads
• Strongest thread produced by the spider
• Used for primary structure in webs
• Used for unique purposes, ie to lasso, quick
  descents, or stringer for flight

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Version of Sticky Silk

• Silk encapsulated in sticky coating
• Surface tension knots silk in regular intervals
• Knotted silk acts similar to a spring when under
  tension by uncoiling from the knot
• The uncoiling process absorbs the energy imparted
  onto the silk from an external force, ie bug
• The silk recoils into the knot once the force is
  removed

Top Magnification of Spider silk (100x) Bottom
Magnification of Spider silk (300x) (Ref. 1)
9
Elasticity of Spider Silk

• Spider silk of Stegodyphus Sarasinorum spider
• Left Silk in initial configuration
• Middle Silk stretched to 5x original length
• Right Silk stretched to 20x original length

10
Stress and Strain Correlations

• Stress Strain Curve for Orb Weaver Spider,
  Araneus Diadematus
• Linear stress strain relation as fracture is
  approached

(Ref. 3)
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Modulus Stress Correlations

• Spider silks Modulus of Elasticity increases
  with increases stress until fracture is reached
• The increase in Modulus suggests the initial
  configuration of the silk elongates more than the
  higher stressed state of the silk

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Why Spider Silk Is Not in Current Use?

• Spiders can not be raised well together
• Territorial
• Cannibalistic
• Large numbers of spiders must be available to
  harvest an adequate amount of silk
• Spiders tend not to be regularly cooperative
• Time, effort, and expense to harvest silk from
  spider is not feasible

13
Alternatives to Spider Silk?Goat Silk?

• Genetic engineering has inserted the gene the
  allows spiders to produce silk into bacteria
• This gene has been successfully integrated into
  goats
• Mammary gland is capable of producing complex
  proteins like spider silk
• The goats milk will contain spider silk fibers
• Goats will pass spider silk gene onto offspring
• Goat silk can then be extracted from the milk and
  spun into threads

14
Future Applications

• Spider silk can improve or replace existing
  materials, ie Kevlar or composite ingredients
• Super strong parts
• Strand of spider silk pencil thick can stop a
  Boeing 747

(Ref. 4)
15
Conclusions

• Spider silk is one of the strongest materials
  known to man
• Spider silks properties come from detailed
  structure and composition
• Researching naturally made fibers gives insight
  into natures intricacies
• Emulating natures methods of producing these
  fibers
• Investigation of fibers intricacies will provide
  a means for improving
• Development of spider silk as a usable material
  will improve existing technologies and pave the
  way for currently unobtainable technologies

16
References

• 1) http//www.hyahya.org/themiracleinthespider05.p
  hp
• 2) http//www.mhhe.com/biosci/genbio/life/articles
  /article1.mhtml
• 3) http//www.tiem.utk.edu/mbeals/spider.html
• 4) http//community.webshots.com/photo/429261/5350
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