With recent advancements in the direct electrostatic printing of highly viscous thermoplastic polymers onto an automated collector, melt electrospinning writing technology (MEW) has shown great potential for addressing the fundamental effects of an engineered scaffold’s dimensional parameters (e.g. fiber diameter, apparent pore size, and pore shape) on cultured cell–scaffold interactions. The superior resolution obtainable with MEW compared to conventional extrusion-based 3D printing technologies and its ability for toolpath-controlled fiber printing can facilitate the creation of a complex cell microenvironment or niche. Such a cell niche would provide the microscale fiber diameter and pore size for a scaffold substrate to present dimensional cues that affect downstream cellular function. In this study, the authors present in detail the design of a custom MEW system that allows simultaneous thermal management in the material, spin-line, and collector regimes using a heat gun. The complex interplay of process and instrument-based parameters is clarified with respect to stable jet formation allowing the printing of scaffolds with various microstructural patterned cues and consistent fiber diameter in a reproducible manner. Current fabrication of high fidelity scaffolds requires that the ratio of inter-fiber distance to fiber diameter to be an approximate value of 10. Since this manufacturing challenge yields pore sizes that are prohibitively large for 3D cell culture studies, particular emphasis is given in this paper to address the underlying physical mechanisms that will enable the fabrication of pore sizes with MEW scaffolds at cellular-relevant fiber diameters (10 – 50 μm). The authors show that appropriate toolpath planning that takes into account the different modes of the process can improve the inter-fiber distance resolution and thus the scaffold’s apparent pore size.

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