Nature is smart and brilliant. In nature, we can find the best examples on how to biosynthesise a material and use it for several purposes with efficiency. An astonishing case study is the spider silk which is a form protein fibre structurally similar to cellulose and human hair. Looking at the nanoscale, Transmission Electron Microscopy (TEM) analysis performed by Simmons et al.  has revealed an intriguing microstructure without any resemblance with typical man’s made materials: the spider silk is composed of small crystallites with sizes around of 30 nm separated by amorphous regions cross-linking those nanocrystals.
This semi-crystalline microstructure is responsible to deliver a unique set of properties which express the complexity and the beauty of such spider fibres. The tensile strength, 1.30 GPa, is in the order of the stainless steels, 1.65 GPa, with its density corresponding to a sixth of the steels . With extreme ductility, these fibres can be stretched almost up to six times of their unloaded length. In terms of structural integrity, the mechanical properties of the spider silks are hold within the temperature range of -40 to 220°C, unlikely relevant for the natural environments. Darwin’s bark spider silk can reach up to 520 MJ/m³ of toughness: at around 10 times higher than Kevlar toughness .
Are the metallurgists and material scientists able to invent a material inspired by the semi-crystalline spider silk microstructure and make use of its properties? An interesting multidisciplinary field that, nowadays, has attracted the attention of the scientific community is known as biomimetics. Consists in how scientists can interpret nature aiming at the design and synthesis of materials and structures by means of mimicking biological process.
In material sciences, the benefits of adopting an interdisciplinary biomimetic approach could bring enormous consequences to the next generation of researchers and engineers. The simple fact that a biological spider silk with mixed amorphous-crystalline microstructure can give birth to a protein-based material with comparable mechanical strength of the human top-steels is an astonishing achievement.
As pointed out in this blog before, superspecialisation has created an entire generation of professionals without any commitment with nature, environment and wellbeing. We need to go back to our roots. To observe nature as scientists and learn with it. To extract the best that nature can give us, and as a result, produce bio-inspired materials with enhanced properties. The triad metals-ceramics-polymers is old fashion and may condemn the creativity of our students for their entire carrers.
 SIMMONS, Alexandra H.; MICHAL, Carl A.; JELINSKI, Lynn W. Molecular orientation and two-component nature of the crystalline fraction of spider dragline silk. SCIENCE, p. 84-87, 1996.
 SHAO, Zhengzhong; VOLLRATH, Fritz. Suprising strength of silkworm silk. NATURE, 418, 741, 2002.
 BLACKLEDGE, Todd; KUNTNER, Matjaz; AGNARSSON, Ingi. Bioprospecting finds the toughest biological material: extraordinary silk from a giant riverine orb spider. Plos one, v. 5, n. 9, p. 1, 2010.
Featured Image: Darwin’s back spider. Credits: BBC London.