Fig. 1: Electrohydrodynamics (EHD)-based fabrication methods employed in this study.

a Solution electrospinning (SES) vs. melt electrospinning (MES). The main differentiating feature between the two processes is the extent of the jet instabilities that arise from the electrostatic forces acting at the polymer jet-air interface. For MES, the chaotic jet regime is limited close to the grounded collector plate due to the high viscosity and dielectric properties of the pure polymer melt. b Direct melt electrowriting (MEW) and its operating principle. (i) 3D conical fiber structures are obtained by the layered deposition of fibers in circular patterns due to jet instabilities close to the stationary collector plate. (ii) The jet instabilities can be eliminated by moving the grounded collector plate at prescribed translational stage speeds. (iii) Micrograph depicting various fiber topographies that are obtained by tuning the translational stage speed (U_T [SI: mm/s)]. Coiling fiber structures are obtained for the lowest U_T setting. Coiling frequency of these fiber structures can be gradually eliminated by gradually increasing U_T to achieve aligned fibers at the critical U_T setting