Table 1.
Values of thickness, Ra, spread, porosity average, and fiber diameter.
Fig 1.
Optical image of example depositions produced by electrospinning onto the 200, 1100, and 2000 RPM rods.
All depositions span approximately the same length of the mandrel.
Fig 2.
Thickness maps of example depositions onto 200, 1100, and 2000 RPM mandrels plotted against both the azimuthal (Φ, circumferential) and axial (Z, longitudinal) directions.
Fig 3.
SEM images of surface protrusions found following 200 RPM depositions.
(A) Low magnification showing the preponderance of these protrusions and their frequency. (B, C) Higher resolution images revealing the aligned fiber arches found at the ‘peak’ of these features. Images are taken at a ~90° tilt.
Fig 4.
SEM images of the central and edge regions following 200, 1100, and 2000 RPM depositions.
Fig 5.
Porosity maps of example depositions on mandrels rotated at 200, 1100 and 2000 RPM plotted against both the azimuthal (Φ, circumferential) and axial (Z, longitudinal) directions.
Fig 6.
2D representation summarizing the (A) thickness and (B) porosity gradients along the axial direction (z) following depositions at 200, 1100, and 2000 RPM. The solid line represents the mean, and the shaded area represents the range of ± one standard deviations across different depositions (200 and 2000 RPM: n = 4; 1100 RPM: n = 3. See S1 File for details). To emphasize symmetry, the axial coordinates are centered with the as-deposited peak as the origin (z = 0). Thickness and porosity profiles of each individual depositions are available in S2 Fig in S1 File.
Fig 7.
(A) Distribution of pore sizes versus axial positions (z) predicted by Eq (3) with laser metrology-based porosity and fiber diameters. Variations in fiber diameters against positions are neglected, and only values measured in the centers are used. As these variations are small (Table 1) and pore size only scales linearly with fiber diameter in Eq (3), this does not fundamentally affect the results. The solid line represents the mean, and the shaded area represents the range of ± one standard deviations across different depositions. To emphasize symmetry, the axial coordinates are centered with the as-deposited peak as the origin (z = 0). Data for different collector biases (-5 and 0 kV) are derived from our prior work [19]. (B) Major and (C) minor axes of pores measured from deposition center under SEM following 200, 1100, and 2000 RPM depositions.
Fig 8.
Effects of (A) RPM and (B) collector bias (data derived from our prior work [19]) on the mass distribution of depositions along axial (z) direction. Values are calculated from densified thickness and bulk PCL density of 1.145 g/cm3. The solid line represents the mean, and the shaded area represents the range of ± one standard deviations across different depositions. To emphasize symmetry, the axial coordinates are centered with the as-deposited peak as the origin (z = 0).
Fig 9.
(A) Distribution of fiber orientations across axial (0°) to azimuthal (±90°) directions at different RPMs. Orientation-based colorization of SEM images taken from the center of (B) 200, (C) 1100, and (D) 2000 RPM depositions. To achieve better statistical representation, each image is stitched from 50 individual SEM images and covers a net area >2,000,000 μm2. In all three images (B-D), the direction of mandrel rotation (azimuthal, ±90°) is in the vertical direction. Original (un-colorized) images and colormap are available in S4 and S5 Figs in S1 File.
Fig 10.
Projections of final porosity (left-hand y-axis, straight lines) and pore size (right-hand y-axis, predicted by Eq (3), curved lines) versus removal of sacrificial fiber from initial scaffolds having the porosities shown in the legend.
The pore size reported is rendered dimensionless as ratio over fiber diameter.