3D reconstruction of bias effects on porosity, alignment and mesoscale structure in electrospun tubular polycaprolactone

Porosity variations in tubular scaffolds are critical to reproducible, sophisticated applications of electrospun fibers biomedicine. Established laser micrometry techniques produced ~14,000 datapoints enabling thickness and porosity plots versus both the azimuthal (Φ) axial (Z) directions following cylindrical mandrel deposition. These 3D datasets could then be ‘unrolled’ into ‘maps’ revealing 0, −5, −15 kV collector biases. As bias increases, thinner, more ‘focused’ depositions occur. At 0 bias, maximum coincides with porosity; at −5 minimum porosity. maps show that kV, a concave-down central region higher (~93–94%) exists bounded on either side by roughly symmetric, parabolic decreases ~87–89% which corresponds ~15v%. different concave-up character occurs, showing ~82–84% increases ~85–86%. profile shows or linear behavior. Simultaneous net (91.1%@0 > 83.4%@-5 80.2%@-15 kV) sensible, but significant changes distribution were unexpected. Surprisingly, extensive mesoscale surface roughness is evident. Optical profilometry revealed unique features ~1600 × 420 μm size, standing ~210 above surrounding surface. shrink only ~440 150 size ~30 disappear entirely kV. Scanning electron microscopy (SEM) resolved these novel, localized ‘domains’ containing tightly aligned oriented parallel axis. Observation ‘curly’ SEMs indicate buckling instabilities. This agrees prior observations residual solvent effects: increased causes faster motion toward mandrel, meaning (1) its content upon arrival higher, leading lower viscosities less resistant buckling/compaction, (2) velocities during deposition cause decreased porosity/“denser packing” buckling. Unexpectedly, we also observed substantial orientation along By modifying classical bending instability models incorporate electric fields, simulation horizontal components modified field alter loop shape, causing alignment. provides new, easily utilized tool facile, efficient tuning orientation.