What is Spider silk?
Spider silk is incredibly tough and it is stronger by weight than steel. Quantitatively, spider silk is five times stronger than steel of the same diameter. It has been suggested that a Boeing 747 could be stopped in flight by a single pencil-width strand and spider silk is almost as strong as Kevlar, the toughest man-made polymer. It is finer than the human hair and is able to keep its strength below -40°C.
Spider silk is also very elastic and capture silk remains unbroken after being stretched 2-4 times its original length. Spider silk is tougher, more elastic and more waterproof than silkworm silk so it could have a much wider range of applications. It is simple to see why spider silk is of such interest to materials a chemist since new ultra-strong fibres based on the silk could be developed.
Why do spiders need strong silk?
These unique properties of silk are very important for spiders. It takes a lot of energy to build a web. If only a couple of threads break, the spider doesn't have to start building a whole web from scratch. Also, spiders need their webs to catch food. If the web broke every time an insect flew into it, it wouldn't be a very good trap! Instead, the web is flexible enough to stretch when an insect lands in it, strong enough not to break and sticky enough to trap the insect.
How Spiders Works
The main thing that distinguishes spiders from the rest of the animal kingdom is their ability to spin silk, an extremely strong fibre. A few insects produce similar material (silkworms, for example), but nothing comes close to the spinning capabilities of spiders. Most species build their entire lives around this unique ability.
Scientists don't know exactly how spiders form silk, but they do have a basic idea of the spinning process. Spiders have special glands that secrete silk proteins (made up of chains of amino acids), which are dissolved in a water-based solution.