Skip to main content
Research article - Peer-reviewed, 2022

Artificial and natural silk materials have high mechanical property variability regardless of sample size

Greco, Gabriele; Mirbaha, Hamideh; Schmuck, Benjamin; Rising, Anna; Pugno, Nicola M.


Silk fibres attract great interest in materials science for their biological and mechanical properties. Hitherto, the mechanical properties of the silk fibres have been explored mainly by tensile tests, which provide information on their strength, Young’s modulus, strain at break and toughness modulus. Several hypotheses have been based on these data, but the intrinsic and often overlooked variability of natural and artificial silk fibres makes it challenging to identify trends and correlations. In this work, we determined the mechanical properties of Bombyx mori cocoon and degummed silk, native spider silk, and artificial spider silk, and compared them with classical commercial carbon fibres using large sample sizes (from 10 to 100 fibres, in total 200 specimens per fibre type). The results confirm a substantial variability of the mechanical properties of silk fibres compared to commercial carbon fibres, as the relative standard deviation for strength and strain at break is 10–50%. Moreover, the variability does not decrease significantly when the number of tested fibres is increased, which was surprising considering the low variability frequently reported for silk fibres in the literature. Based on this, we prove that tensile testing of 10 fibres per type is representative of a silk fibre population. Finally, we show that the ideal shape of the stress–strain curve for spider silk, characterized by a pronounced exponential stiffening regime, occurs in only 25% of all tested spider silk fibres.


Biomaterials; Soft materials; Structural materials

Published in

Scientific Reports
2022, volume: 12, number: 1, article number: 3507

Authors' information

University of Trento
Swedish University of Agricultural Sciences, Department of Anatomy, Physiology and Biochemistry (AFB)
Mirbaha, Hamideh
University of Trento
Karolinska Institute
Swedish University of Agricultural Sciences, Department of Anatomy, Physiology and Biochemistry (AFB)
Karolinska Institute
Pugno, Nicola M.
Queen Mary University London

UKÄ Subject classification

Bio Materials

Publication Identifiers


URI (permanent link to this page)