Collagen based soft materials are important as medical materials and as consumer products. Strength is a crucial parameter. A better understanding of the structural factors that contribute to strength is sought. Synchrotron based small angle X-ray scattering was used to characterize the collagen fibril structure and structural arrangement in a range of collagen based materials including leather, surgical scaffold materials and glutaraldehyde stabilized pericardium. Structure was compared with strength and was also characterized during strain. When collagen fibrils are orientated in a highly layered structure (with a high orientation index) the materials exhibit higher tear strength. This applies to leather, surgical scaffolds derived from dermis and pericardium. A more layered structure is found in stronger leather, and depends on the species of the source animal and processing conditions. For surgical scaffolds and stabilized pericardium stronger material is found also to have a more layered structure. In pericardium it is affected by the age of the source animal with younger animals having a more layered fibril arrangement in the pericardium. When collagen based soft materials are strained, the material responds first by a reorientation of the fibrils then by extension of individual fibrils, and this enables them to withstand high stresses. 

Graphical Abstract

Fibril orientation and strength in collagen materials and adaptation to strain