Is spider silk the strongest natural material?

We put Joe's tough question to materials scientist Anna Ploszajski, from University College London...

Anna - Spider silk is an example of an exceptional natural material. It’s exceptionally strong and it’s also very, very stretchy. These are two materials properties that we don’t often see come together in a single material. However it is not, unfortunately, the strongest natural material. In February, 2015 it was surpassed by limpet teeth. These can be up to 40 percent stronger than spider silk, and the reason that they’re so strong is that they’re an example of a nano composite.

What we mean by that is that a composite is a combination of two different materials, one of which is at the nanoscale, so very, very, very, very thin. Now this particular material of limpet teeth is made from a protein base and interwoven in that is a dense webbing of very, very tiny nano fibres made from an iron based mineral called goethite. The combination of properties of these proteins and this mineral that give the limpet teeth their incredible strength.

Chris - And they need that incredible strength because?

Anna - Because they’ve got to hang onto rocks no matter what the weather is and no matter what kind of …

Chris - Is it that or is it because they’re scouring stuff off the rocks?

Anna - I’m not actually sure.

Chris - Because they’re grazing, aren’t they, as they go across the rocks surface they’re scraping off algae and things and filtering them into their body?

Anna - OK.

Chris - So I suppose you need something harder than the rock you’re living on otherwise your teeth or going to wear away really fast?

Anna - Indeed. Not only harder but stronger as well. So yeah, the material properties required are pretty intense for these poor little limpets.

Chris - So spiders are trumped!

Anna - Yeah!