Fig. 4.

(a) Traditional electrospinning apparatus containing a high-voltage power supply, a syringe with spinneret, a syringe pump, and a grounded collector. Schematic illustration of electrospun fibers preparation: (a_i) formation of surface charged droplets (a_ii) extrusion of the solution from the syringe generating a tiny conical droplet. (a_iii) “Cone-jet” regime where a fine jet initiates from the cone. (b) SEM images of electrospun fibers randomly oriented. Electrospinning set-ups, such as (c) mechanical, (d) electrostatic, and (e) magnetic forces to adjust pore structure and fiber orientation. The right column shows the aligned nanofibers prepared by different electrospinning set-ups. (a–b) Schematic diagram inspired from Ref. [140]. (c–e) Schematic diagram inspired from Ref. [149]. (c; right column) Adapted from Ref. [149] with permission of Copyright 2011 Wiley-VCH. (d; right column) Adapted from Ref. [145] with permission of Copyright 2010, American Chemical Society. (e; right column) Adapted from Ref. [147] with permission of Copyright 2010 Wiley-VCH.