The charm of the silk fabric has allured mankind since thousands for years. The dazzle, broad range of colors and the excellent texture has made this fabric - the most amicable of all. Silk fabric is manufactured by both, naturally and artificially. There are four types of natural silk is available, namely tasar, mulberry, muga and eri. However, the higher demand for natural silk led pressure to find out other options to make silk. The four natural silk sources seem incapable to cater the increasing demands. Now here a significant question arises - Is there any other source available to get natural silk? The answer is "YES", it's a "Spider Silk". It is true that irritate ting and ignored insect can produce good silk fibre.
Spider silk is a fibre, which is extracted from spiders. It is strong fibre, even its tensile strength is compared to the steel. The tensile strength for one type of steel at 1.65 Gpa, whereas spider silk is nearly at 1.3 Gpa. But, the density of spider silk less than steel and its tensile strength to density is about five times more than steel, such as DuPont's Kelvar, aromatic nylon filaments.
Spider silk's Structure
Within a distinctive fibre, there are crystalline sectors with amorphous linkages. These crystal sectors are beta-sheets, which are put together. Spider silk is very flexible, and can be stretched up to 40 percent of its original length with no breakage problems. This results in a high ductility. Liquid crystalline spinning of spider silk is similar to aromatic nylon.
Spider silk is made of complex molecules of protein. Spider can't be farmed such as silkworms, as they are cannibals. Due to this nature they even eat each other. The silk extracted is very fine, thus to make one square yard cloth 400 spiders are require. The fibre gets harden when it is exposed to open air that creates a problem to work with. Because of the repetitive symptoms of the DNA encoding it is difficult to recognize its sequence. Only from 14 species the protein has been decoded.
Although various protein sequences are found in different, a common in spider silk structure is a sequence of amino acids, which self-assembled into a beta sheet group. The Ala rich blocks are distinguished by segments of amino acids with heavier side groups. The beta sheets gathers to make crystals, on the other side, other segments makes amorphous domains. The interaction between the crystalline segments and elastic amorphous regions results exclusive spider silk properties.
Spider Silk Origin
The silk gland releases the fibre. Different spider species have different glands for their own reason like web-creation, housing, capturing the prey and defense. The visible part of the gland is called as the spinneret. The initial part of the gland is full of thiol and tyrosine, the key ingredients in silk fibre. After making of fibres, the ampulla plays role of a storage box. Here, spinning duct sweeps-off water from the fiber and small channels also help in this process. Liquid separation is conducted at the verge the distal limb of the duct, and further passes to the valve. The valve is anticipated to help in fixing broken fibers again, playing more in the path of a helical pump.
Artificial spider silk
It is not usually possible to utilize spiders to produce spider silk in enormous quantity to cater industrial demands, because it is hard to manage huge number of spiders. Steps have taken in extracting the spider silk gene and using other options to manufacture the needed quantity of spider silk. In year 2000, a Canadian biotechnology company, Nexia was successful in making spider silk protein in goats.
These goats hold the spider silk protein gene, and the milk produced contained considerable amount of the protein. However, the trials were unsuccessful to spin the protein into a fibre equivalent to the natural spider silk.
The spider's spinneret is able in turn the silk proteins into strong domains. Particularly, the spinneret makes an incline of protein concentration, pH and pressure that leads the protein blend through liquid crystalline transitions, resulting creation the required silk structure. Imitating this process in laboratory has been witnessed very tough. Nexia tried to imitate this process by pressing the solution of protein via fine holes; however, this was inefficient trial to manage the fibres appropriately.
Spider Silk Applications
Recent research in the spider silk includes its potential utilization as an extremely strong and versatile thing. The interest in producing the spider silk is mostly due to a blend both, its mechanical properties and the non-polluting option. The manufacturing of latest man-made fibres like Dupont's Kevlar, are made from petrochemical processing that results massive pollution. On the other hand, the manufacturing of spider silk is entirely environment-friendly, as it is produced by spiders at normal temperature, pressure and water, without any pollution. Additionally, spider silk is fully biodegradable. If the production of spider silk increases, it may replace Kevlar and can be used to range of products like bullet-proof clothing, wear-resistant lightweight clothing, topes, nets, seat belts, parachutes, rust-free panels on motor vehicles or boats, bio-degradable bottles and medical items.
The spider silk has raised an open challenge to scientist, engineer, spinner and weavers to manage its development and to get acquainted with inherent skills of spider in making the silk thread.