Production and cross-sectional characterization of aligned co-electrospun hollow microfibrous bulk assemblies

The development of co-electrospun(co-ES) hollowmicrofibrous assemblies of an appreciable thickness is critical for many practical applications, including filtration membranes and tissue-mimicking scaffolds. In this study, thick uniaxially aligned hollow microfibrous assemblies forming fiber bundles and strips were prepared by co- ES of polycaprolactone (PCL) and polyethylene oxide (PEO) as shell and corematerials, respectively. Hollowmi- crofiber bundles were deposited on a fixed rotating disc, which resulted in non-controllable cross-sectional shapes on a macroscopic scale. In comparison, fiber strips were produced with tuneable thickness and width by additionally employing an x–y translation stage in co-ES. Scanning electron microscopy (SEM) images of cross-sections of fiber assemblies were analyzed to investigate the effects of production time (from 0.5 h to 12 h), core flow rate (from 0.8 mL/h to 2.0 mL/h) and/or translation speed (from 0.2 mm/s to 5 mm/s) on the pores and porosity.Weobserved significant changes in pore size and shapewith core flowrate but the influence of production time varied; five strips produced under the sameconditions had reasonably good size and porosity reproducibility; pore sizes didn't vary significantly fromstrip bottomto surface, although the porosity gradually decreased and then returned to the original level.