Spider silk - what is spider silk

Spider Silk is a natural fiber secreted by spiders for the production of webs and egg sacs as well as transportation.. It is the interplay between the hard crystalline segments, and the

Spider Silk

Prepared By : Mazadul Hasan sheshir ID: 2010000400008

13th Batch (session 2009-2013) Department : Wet Processing Technology Email: mazadulhasan@yahoo.com

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Southeast University

Department Of Textile Engineering I/A 251,252 Tejgaon Dhaka Banglade sh

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Spider silkaby Spider Silk is a natural fiber secreted by spiders for the production of webs and egg sacs as well as transportation Spiders use theirmakeother structures, which function as nets to catch other animals, or as nests or cocoons for protection for their offspring They can also suspend themselves using their silk The silk is secreted from glands inside the spiders spinnerets, located on the back of a spiders abdomen Spider silk is renounced for being stronger than steal by mass and is surprisingly elastic and has generated interest for an array of applications Allegedly, these properties are a result of both its structure and chemical make up

What is Spider Silk?

Spider Silk?

Extraction and weaving of Spider Silk

1 Silks have a hierarchical structure (e.g., cellulose, hair)

2 The primary structure is its amino acid sequence, mainly consisting of highly repetitive glycine and alanine blocks

3 On a secondary structure level, the short side chained alanine is mainly found in the crystalline domains of the nanofibril, glycine is mostly found in the so-called amorphous matrix consisting of helical and beta turn structures It is the interplay between the hard crystalline segments, and the strained elastic semi-amorphous regions, that gives spider silk its extraordinary properties

Structure

Cross section of spider silk showing

Cluster of round spots of varying size and

fibers are extremely circular Cluster of

round spots of varying size and fibers are

extremely circular

Cross section of silk worm fiber showing Triangular shape and fibers are held by mercerized cotton to help support the fiber when they are cut

Figure: Under microscope with partially cross polarized light to help enhance their structure

Comparison of golden orb spider silk with cultivated silk worm moth bombyx mori

Longitudinal view of spider silk fiber

showing TWO distinct fiber types Thicker

more homogeneously yellow fiber are the

fibers with all the incredible physical

properties

Longitudinal view of silk worm fiber showing thinner white or colorless fiber

Figure: Under microscope with partially cross polarized light to help enhance their structure

Spider Silk Vs Cultivated Silk

1 In 2000, Canadian biotechnology company Nexia successfully produced spider silk protein in transgenic goats that carried the gene for it; the milk produced

by the goats contained significant quantities of the protein, 1–2 grams of silk proteins per liter of milk Attempts to spin the protein into a fiber similar to natural spider silk resulted in fibers with tenacities of 2–3 grams per denier

2 In March 2010, researchers from the Korea Advanced Institute of Science & Technology (KAIST) have succeeded in making spider silk directly with the bacteria E.coli, modified with certain genes of the spider Nephila clavipes Thus, this eliminates dependency on the spider for milking and allows to manufacture the spider silk at a more cost-effective manner

Recent attempts to develop materials with comparable properties to

Spider Silk

Spider silk has amazing physical properties They are

1 Extremely elastic

2 Extremely strong

3 Stronger than Kevlar

Amazing Properties Of Spider Silk

Spider silk provides the best balance of strength and toughness as shown in the

stress-strain curve

· The stress-strain curve of the spider silk assumes a sigmoidal shape similar

to that of an elastomer, demonstrating a well balance of strength and

elongation at 1.75 GPa (15.8 g/den) and 36%, respectively

· This "rubber-like" stress-strain curve is characterized by three distinct

regions:

Region I (0-5%) is characterized by a high initial modulus of 34 GPa;

Region II (5-21%) shows a pseudo yield point at 5 % before strain

hardening to a maximum modulus of 22GPa at 22% elongation and

Region III (21-36%) exhibits a gradual reduction of modulus until reaching failure strength of 1.75 GPa at 36% elongation

· An examination of the area under the stress-strain curves shows a toughness level of 2.8 g/denier This is much higher than the toughness of the aramid fiber (0.26 g/denier) and nylon 6 fiber (0.9 g/denier)

Amazing Properties Of Spider Silk

Mechanical properties of Spider Silk

Mechanical properties

Most spider silk have exceptional mechanical properties They exhibit a unique combination of high tensile strength and extensibility (ductility) This enables a silk fiber to absorb a lot of energy before breaking (toughness, the area under a stress-strain curve)

Strength

In detail a spider silk’s tensile strength is comparable to that of high-grade alloy steel (450 - 1970 MPa),and about half as strong as aramid filaments, such Kevlar (3000 MPa)

Extensibility

Silks are also especially ductile, with some able to stretch up to four times their relaxed length without breaking

Toughness

The combination of strength and ductility gives dragline silks a very high

toughness (or work to fracture), which "equals that of commercial

polyaramid (aromatic nylon) filaments, which themselves are benchmarks of

modern polymer fiber technology"

Figure: Tensile Stress-Strain Curves of Spider Silk and other Polyamide Fibers

Mechanical properties of Spider Silk

Potential of spider silk:

1 Military and medical arenas

2 Experiments with producing synthetic fibers

3 Use of spider silk in bio medical application

4 Component of artificial tendons and ligaments

5 Guides for re growing nerves

6 Scaffold for tissue growth

Application of spider silk

Figure: Bio-artist Jalila Essaidi, used spider-goat silk to create "bulletproof skin", and a 22 caliber bullet, fired at a reduced speed, hitting but not breaking the skin

Application of spider silk

Scientists mix in metal to make super-strength spider silk

Scientists have now found that they can make spider silk even tougher by infiltrating some metal atoms into the spider's handiwork To get the metal into preexisting dragline silk, the authors used an atomic layer deposition technique, which uses repeated pulses of vaporized material that contains metals In this case, they tried several metal compounds, including diethyl zinc, trimethly aluminum, and a titanium compound, all vaporized in the presence of water Water alone was used as a control All of the compounds dramatically increased both the tensile strength of the silk, as well as its extensibility In short, the researchers had taken an unusually tough material and made it even tougher, with the best results produced by the aluminum and titanium treatments

Application of spider silk

Scientist Uses Spider Silk for Violin Strings

Spider silk is turning out to be a remarkably versatile material Aside from having

a higher heat conductivity than any other organic matter and proteins for inserting genes into cells, strings from a spider have also been found to have a very high tensile strength One researcher in Japan has studied this property of spider silk for decades, and recently unveiled a new application for it by weaving together thousands of strands of spider filaments and using them as violin strings

Application of spider silk

Spider Silk as Artificial Muscle

Scientists at the University of Akron have developed two new ways to apply spider silk, and normal silk from silkworms, to artificial muscles If refined and commercialized, scientists say the silk could be used in everything from robotics to microchip systems

Like human muscle, spider silk muscles would have degrees of movement, depending on the amount of water in the air around the muscle High humidity would mean maximum contraction, low humidity would loosen the treads Water breaks apart the hydrogen bonds inside the thin strands of protein, causing new, contracting bonds, to form As the water evaporates the hydrogen bonds reform in their original positions

Application of spider silk

INFORMATION & CAUTECY

Md Salim Azad Didar I.D: 201000400038 Batch: 13th-1

Department : Wet Processing Technology Southeast University

Department Of Textile Engineering

1 Zemlin, J C., A Study of the Mechanical Behavior of Spider Silks, U S Army Natick Report AD 333, 19

2 www.wikipedia.com

3 Kaplan, D., Adams, W W., Famler, B., and Viney, C., editors, Silk Polymers: Materials Science and Biotechnology, ACS Symposium Series 544, American Chemical Society, DC

4 Marples, B J., "The Spinnerets and Epiandrous Glands of Spiders", J Linnean

Soc.Zoology)

5 Cheryl Hayashi_ The magnificence of spider silk_TED

REFERENCES