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

Abstract

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.

Development of an electrospinning method for the tensile testing of single nanofibers

“…Tensile strength was 223 ± 75 MPa. For PLLA nanofibers, tensile strength was reported as 204 ± 86 MPa [8], which is close to our result. The stress-strain curve in Fig.9 consists of two linear stages, which is similar to that of the case of polyimide nanofibers [9].…”

Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers

“…These values are approximately one order of magnitude higher than the value of 23.8 GPa reported by Zhang [18] and 15.1-22.5 GPa reported by Zhao [12], which can be explained by the differences in the structure and diameter of the fibers. Higher Young's modulus values for annealed nanofibers compared with untreated nanofibers may be caused by the higher crystallinity of the α-phase, thereby leading to an improvement in the mechanical properties [28]. An increase of crystallinity for annealed alumina nanofibers is found in the XRD patterns ( Fig.…”

Engineering on the Straight and Narrow: The Mechanics of Nanofibrous Assemblies for Fiber-Reinforced Tissue Regeneration

“…100 Similarly, the AFM probe tip has been used to carry out three-point bending tests of individual fibers placed over a groove microetched into a silicon wafer. 101 Still more recently, specialized MEM devices have been constructed that couple with AFM cantilevers, and have been used to show the dependence of ultimate strain on applied strain rate for polyacrylonitrile nanofibers.…”