As kids, we would have watched
the amazing comic hero Spiderman hanging upside down, swinging and shooting his
spider silk all across the city. Little would have we thought, if such fragile
looking fibres would be able to pull or handle such heavy weight. The
flabbergasting fact behind these fibres is that its elasticity enables the
fibre to be stretched from five to twenty times of its normal length, and has
the resistance of steel that it can also be used as a rip proof fabric.
'Spider silk' is one of the most sought after biomaterial. Also known as 'gossamer', this is a protein fiber spun by spiders. Due to its demand, and unavailability, it has even acquired the nickname, 'Holy Grail". This silk comes from the glands of the spider and is both flexible and lightweight. For a spider, this fibre is used for catching its prey, serves as a life line while jumping, and a place to nest its egg. As far as the human side is concerned, the silk is used in making bullet proof clothing, rust-free panels on motor vehicles, surgical thread etc.
These fibres are flexible, waterproof, and one of the toughest materials in the world. They are extremely weightless that a fibre long enough to cover the world would only weigh less than 170 grams. The fibres are flexible enough to be stretched upto 40% of its original length, without any breakage problems, which give high ductility to the strands. Despite the fact that they are identical to that of the silkworm, spider silk lacks commercial value. Fabrics from spider silk lacks luster. Due to the difficulty in encoding the silk protein, it is a tedious task to identify the sequence, and till today, only 14 species of silk producing spiders are decoded.
Types of Spider Silk:
Different spiders have different glands for producing different kinds of silk, and for different reasons, like web construction, capturing prey, defense, or mobility. Each fibre gives a different kind of silk.
- Dragline silk: This fibre is used as the outer rim of the web. It is tough, and strong as steel.
- Tubiliform silk: This fibre is used for protecting egg sacs. Its nature is very stiff.
- Capture-spiral silk: This fibre is extremely sticky, and stretchy by nature, and is used for the capturing lines of the web.
- Minor-Ampullate silk: This fibre is used for web construction purposes.
- Aciniform silk: This fibre is used to wrap the captured prey. This is three times tougher than the dragline silk.
Possible Applications of Spider Silk:
Spider silk applications have been in vogue for more than thousands of years. The Greeks used them to stop bleeding from wounds. On devices such as telescopes, and guns, it is used as crosshairs. Some people use it as fishing nets. In the present day, this fibre has the following potential applications.
- Used for making artificial tendons and ligaments for supporting weak blood vessels.
- For making rust-free panels on motor vehicles or boats.
- Making bandages and surgical threads.
- Manufacturing rip-proof, and light weight clothing.
- Making biodegradable bottles.
- Can be used in ropes, seat belts, and parachutes due to its tensile strength.