Melt Electrospinning Writing Process Guided by a “Printability Number”

Abstract

The direct electrostatic printing of highly viscous thermoplastic polymers onto movable collectors, a process known as melt electrospinning writing (MEW), has significant potential as an additive biomanufacturing (ABM) technology. MEW has the hitherto unrealized potential of fabricating three-dimensional (3D) porous interconnected fibrous mesh-patterned scaffolds in conjunction with cellular-relevant fiber diameters and interfiber distances without the use of cytotoxic organic solvents. However, this potential cannot be readily fulfilled owing to the large number and complex interplay of the multivariate independent parameters of the melt electrospinning process. To overcome this manufacturing challenge, dimensional analysis is employed to formulate a “Printability Number” (NPR), which correlates with the dimensionless numbers arising from the nondimensionalization of the governing conservation equations of the electrospinning process and the viscoelasticity of the polymer melt. This analysis suggests that the applied voltage potential (Vp), the volumetric flow rate (Q), and the translational stage speed (UT) are the most critical parameters toward efficient printability. Experimental investigations using a poly(ε-caprolactone) (PCL) melt reveal that any perturbations arising from an imbalance between the downstream pulling forces and the upstream resistive forces can be eliminated by systematically tuning Vp and Q for prescribed thermal conditions. This, in concert with appropriate tuning of the translational stage speed, enables steady-state equilibrium conditions to be achieved for the printing of microfibrous woven meshes with precise and reproducible geometries.

Role of offset and gradient architectures of 3-D melt electrowritten scaffold on differentiation and mineralization of osteoblasts

“…Several strategies can be utilized to attain porous scaffolds. As melt-electrowriting fabrication delivers a stable electrostatically drawn jet without whipping or random fibre deposition (as in solution electrospinning) it can be used for the formation of gradient structures mimicking native bone by precisely controlling fiber placement [23]. The proliferation and differentiation of cells within 3D scaffolds are affected by both the size and geometry of the scaffold's pores [24] but it's not clear however whether scaffolds with a uniform pore distribution of homogenous size, or constructs with a varying pore size distribution, are more suitable for bone regeneration applications.…”

Rheological Characterization of Biomaterials Directs Additive Manufacturing of Strontium‐Substituted Bioactive Glass/Polycaprolactone Microfibers

“…However in our experience, the bulk rheological properties of PCL/SrBG composites prevent their extrusion via MEW into ordered scaffolds at SrBG concentrations above 10 wt% . This has motivated research to understand both the material properties governing printability and to provide a systematic framework to fabricate MEW scaffolds using novel, complex, and composite biomaterials.…”

Biomimicry in Bio-Manufacturing: Developments in Melt Electrospinning Writing Technology Towards Hybrid Biomanufacturing

“…They could achieve a high-volume structure of more than 7 mm. A further key factor in MEW is the heat and charge distribution in the syringe and nozzle, and between the collector and nozzle, respectively, which determines the viscosity of the polymer and the electric force behavior [43,44,56]. Many parameters as printer's head/collector speed, electric field, back pressure, temperature, and tip-to-collector distance must be in harmony in order to get a highly ordered filament deposition as "writing".…”

“…In order to apply pressure, the majority of studies used a pneumatic system in their setup with higher control on the applying force [51], rather than that syringe pump [62], screw-extruding, and mechanical feeding [46,63]. The collectors are also divided into two general categories as static [53] and rotating [43]. The rotating cylindrical collectors enable various types of geometries, like tubular structures [3,64,65].…”

“…It also provides the opportunity of using multimaterials at once that either is not possible to find a common solvent, or it will cause difficulties for electrospinning [42]. Similar to SE, the polymer jet is subjected to pulling (electrostatic Columbic and gravitational) and resistive (surface tension and viscoelastic) forces at spinneret tip [43,44]. However, the polymer melt with much higher viscosity and lower conductivity lead to more stable jet during the deposition, which makes it easier to obtain a controlled-shape filament.…”