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.
Properties:
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.
