Schematic representation of a fiber (a) in a cylindrical shell as an array of beads connected by Maxwell’s elements and (b) bead surrounded by adjacent beads.
An equilibrium phase diagram of a polymer-solvent system, showing the binodal and spinodal lines demarcating the stable, metastable, and unstable regions.
The morphology of the polymer fiber calculated under the conditions of , flow rate of , and initial polymer concentration of 3%, showing textureless fiber. The dimensionless and material parameters were given in Table I. Note that the fiber was magnified 250×.
Temporal evolution of phase separated domains on the surface of the electrospun microfiber, exhibiting the phase transformation from (i) a stable single phase changing to (ii-iv) two-phase morphologies along the spinline. The structures evolve and get elongated as the microfiber wiggles more violently as it approaches the collector plate. The parameters utilized for this calculation were and . Note that the fiber was magnified 60×.
(a) Phase diagram of a polymer/solvent system, showing (b) effect of temperature of electrospinning (at ) on morphology development subject to the concentration sweep as the system passes through various coexistence regions of the phase diagram encompassing metastable and unstable regions before exiting to the single phase. (c) The enlarged versions show (i) formation of polymer droplet morphology from a single phase dilute solution and crossing over to (ii) bicontinuous and (iii) porous structures, and then exiting to (iv) a polymer-rich single phase. In the grey scale bar, the black color indicates the solvent concentration. The starting polymer concentration was 3% and the final polymer concentration at the collector was indicated by the open circles. Note that the fiber was magnified 250× for (b) and 4000× for (c).
Effect of starting polymer concentration on morphology of the surface of the electrospun fibers at and , showing the structure development for different starting concentrations at (i) 6%, (ii) 10%, and (iii) 20%. Note the fiber was magnified 250×.
Effect of flow rate on the fiber dynamics at and . The flow rates utilized are (a) , (b) , and (c) . Increasing flow rate enhances the amplitude, but reduces the periodicity of whipping instability. Note that the fiber was magnified 60×.
Effect of applied voltage on the fiber dynamics at showing the reduction of the amplitude of instability with increasing . The values of (a) , (b) , and (c) were used in the calculation. Note that the fiber was magnified 125×.
Materials and dimensionless parameters utilized in the simulations.
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