Multiscale SAXS/WAXD characterisation of the deformation mechanisms of electrospun PCL scaffolds

Abstract

This research provides a thorough study of the mechanical response of PCL scaffolds and determines their deformation micromechanisms at different scales by a combination of experimental techniques (mechanical tests, scanning electron microscopy, wide angle X-ray diffraction and small-angle X-ray scattering). Scaffolds with different fibre orientation distribution functions were manufactured and subjected to tensile loading. The macromechanical properties were dictated the by the fibre deformation and interaction in terms of fibre straightening, rotation and stretching. The stiffness and the yield strength were directly proportional to the percentage of fibres oriented with the loading direction. The gradual deformation induced a progressive fibre rotation, uncurling and stretching, showing different impact at molecular level for each configuration. The fibres aligned with the loading direction presented a homogeneous plasticity with an inherent loss of the crystal phase, meanwhile the misaligned fibres exhibited a negligible loss of crystallinity due to a predominance of the fibre rotation. The fibre plasticity triggered the macromechanical yielding of the scaffold and for high levels of plastic deformation the fibres developed macromolecular fibrils and microvoids. These findings provide the fundamental observations to develop engineering tissues with highly tunable and tailored mechanical properties for site specific in vivo applications.