Toughness is the measurement of the material resistance to breakage.
The structure of every material at micro- and nanoscale influences its mechanical properties.
What is so special in spider web at the nanoscale?
Spider web is made of protein based silk fibres. Proteins are resilient (stretchy) and give elasticity to the material design. Silk fibres ranging from 1 to 10 microns contain oriented nanofibrils with a size of 100-200 nm and elongated tubular cavities. Those vacuoles, called canaliculi, control crack propagation during the process of fibres stretching. Consequently, the spider webs have huge strain to failure, which increases material toughness.
As far as a material design is considered, natural silk offers very attractive balance of toughness and stiffness together with viscoelastic properties. The material properties are controlled by molecular bonding between characteristic groups of atoms; in silk it is a combination of hydrogen bonding between peptide segments and van der Waal’s forces.
Concluding, in order to catch a few insects spiders need to make a web made out of silk, which is three times stronger than steel. Spider’s life must be then tough :)
Scanning electron microscopy image of silk fibres from spider web taken from Miriam’s garden.
