Effects of annealing on the structural and mechanical properties of electrospun polymeric nanofibres

Biodegradable polymeric nanofibres produced by electrospinning have been used as scaffolds for tissue engineering. Before these nanofibrous scaffolds can be implanted into the human body, it is important to know if the individual nanofibres are strong enough to withstand the forces exerted by the cells as they grow and migrate on the scaffold. However, due to the small size of the nanofibres, it is a challenge to characterize the mechanical properties of individual nanofibres. Therefore, we aim to mechanically characterize a single nanofibre using both a tensile test and a nanoscale three-point bend test. As some scaffolds may be heat-treated by annealing to enhance the stiffness and strength of the nanofibres, we also investigate the effects of annealing on the structural and mechanical properties of single nanofibres. The material properties of as-spun and annealed nanofibres were studied using differential scanning calorimetry and atomic force microscopy. Annealing was found to increase the Young's modulus of the nanofibre mainly due to the increase in crystallinity and the change in morphology from a purely fibrillar structure to a mixture of fibrillar and nano-granular structure with enhanced interfibrillar bonding.