Filament-Based Melt Electrowriting Enables Dual-Mode Additive Manufacturing for Multiscale Constructs.

Melt electrowriting (MEW) is an electric-field-assisted fiber-forming biofabrication strategy for the additive manufacturing (AM) of precisely defined 3D microarchitectures. MEW is based on pressure-driven extrusion of a polymer melt pool, currently mainly implemented at laboratory scale with specialized machine technology and limited to only few materials. This precludes the accessibility of MEW to a broader user group and can become the bottleneck of MEW's technological advancement. In contrast to conventional MEW, a filament-based approach (F-MEW) is introduced that exploits the technological ecosystem of fused filament fabrication (FFF), a globally used transformative AM technique. In this work, a polymer filament serves as feedstock material and is melted just on demand. By upgrading existing FFF systems, MEW of polymer microfibers is enabled, as validated with polycaprolactone (PCL) and demonstrated with direct writing of thermosensitive polydioxanone (PDO). Finally, FFF and F-MEW are hybridized in a dual-mode AM process. This enables multiscale constructs featuring both FFF struts and one order of magnitude smaller F-MEW microfibers. This work opens the accessibility of F-MEW to the large FFF user group, potentially benefitting from the plethora of filaments available for FFF, while, at the same time, expanding the FFF fabrication window.