How Come Spider Silk Is So Strong?

Spider silk, the silk that a spider uses to spin its web with, has now been recognized as one of the strongest materials ever found. So strong, in fact, that scientists are trying to produce these artificially for use in the construction of super-structures, body armour, etc. This is surprising, because the silk web of a spider looks frail and delicate to the naked eye. The reason behind this strength may be in the genes of the spider.

The basic premise for the strength of the silk is the speed with which it is woven out of the spider's body. However, there is more to it than just the speed. Scientists have been carrying out genetic research to find out the cause of this strength. They discovered that the fibroin molecule of this silk consists of two elements – well-organized and structured microcrystals and meshed up tangles that are amorphous. The microcrystals occupy 20 to 25 percent of the molecular space, and help establish the linkage between different fibroin molecules. The amorphous tangles, on the other hand, are dry and rigid, though unlike glass, which is rigid and brittle as well. These tangles cause the stiffness of the fibres. On being pushed around, the silk tangles straighten out, and allow the silk itself to stretch without snapping off. This is what causes the extreme strength and flexibility of spider silk. Spider silk can be stretched by about 5 percent and still retain its original shape, unlike Kevlar, which can be stretched by about 3 percent only.