Surface-porous and hollow poly(lactic acid) (SPH-PLA) and surface-porous and lotus-root-like PLA (SPL-PLA) nanofibres: preparation, quantitative analysis, and modelling

In this study, PLA nanofibres with unique microstructures were prepared by coaxial electrospinning. The cross-section of the prepared PLA nanofibres exhibited either a surface-porous hollow structure (SPH-PLA) or a surface-porous lotus-root-like structure (SPL-PLA). The morphology, hollow proportion, and porosity of the fibres under different electrospinning parameter conditions were analysed quantitatively; further, three-dimensional (3D) models of the PLA nanofibres were established under parameter conditions that provided the highest hollow proportion. The results of the analysis revealed that the diameter fluctuated only slightly with the process parameters. Additionally, variations in the different electrospinning parameters caused only a slight change in the surface porosity (i.e. only 31% ± 4%) of the PLA fibres. The total porosity of the section (termed the pore porosity), porosity of the hollow section (termed the hollow porosity), R value (R = hollow porosity/pore porosity), and number of small pores of the SPH-PLA nanofibres did not change significantly with the receiving distance; the change observed was approximately only by 38% ± 2%, 28% ± 2%, 75% ± 5%, and 11 ± 1, respectively. Further, the cross-sectional porosity of the SPL-PLA nanofibres also did not change significantly with the receiving distance, only by approximately 24% ± 2%. The hollow proportion was the highest (76.32% ± 8.34%) at a core/shell flow rate ratio of 0.3:0.9 (mL/h), spinning voltage of 19 kV, and receiving distance of 6 cm. Therefore, 3D models of the SPH-PLA and SPL-PLA nanofibres were established under these electrospinning parameters.