How Strong is Spider Silk?

Thought spiders were mere creepy crawlies? Think again. Spider silk is one of the strongest protein fibres in the world. In fact, in terms of tensile strength, which is the maximum amount of stress a material can endure before breaking, spider silk is five times tougher than steel. If it was converted to human size, it would be strong enough to stop a jetliner in its flightpath.

The incredible properties have garnered attention from companies hoping to utilise the potential of spider silk for a host of commercial and industrial applications. Now, a team of scientists have unravelled the mystery of what makes spider silk so strong.

A complex web of nanostrands

They started by analysing the silk of a brown recluse spider using an atomic force microscope. They observed that each strand is made up of thousands of parallel nanostrands, which bind together to create a single thread. To put this into perspective, a complete strand is 1000 times thinner than a human hair, which means the diameter of each nanostrand measures in at just 20 millionths of a millimeter.

Until now, little has been known about the composition of spider silk. The breakthrough was thanks to the brown recluse spider, which spins its silk in a unique flat ribbon pattern in comparison to the cylindrical shape adopted by most species. This made the silk easier to analyse under a microscope and offered a new perspective on what makes spider silk so strong. The team also discovered the use of a complex "sewing" technique that sees the brown recluse spider weave around 20 microloops into every millimeter of its web. This reinforces the spool and helps to create a fibre that boasts more tensile strength than steel.

Harnessing the strength of spider silk

The findings represent a major leap forward for companies hoping to manufacture synthetic spider silk and recreate one of the natural world's toughest materials. For humans, this could mean the harnessing the strength of spider silk to manufacture shrapnel-resistant military clothing, parachute fabric and bike helmets. Spider silk is also biocompatible, which means it could be used for medical applications like internal and external stitches.

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