Melt Electrowriting of Nylon-12 Microfibers with an Open-Source 3D Printer

This study demonstrates how either a heated flat or cylindrical collector enables defect-free melt electrowriting (MEW) of complex geometries from high melting temperature polymers. The open-source "MEWron" printer uses nylon-12 filament and combined with a heated flat or cylindrical collector, produces well-defined fibers with diameters ranging from 33 ± 4 to 95 ± 3 µm. Processing parameters for stable jet formation and minimal defects based on COMSOL thermal modeling for hardware design are optimized. The balance of processing temperature and collector temperature is achieved to achieve auxetic patterns, while showing that annealing nylon-12 tubes significantly alters their mechanical properties. The samples exhibit varied pore sizes and wall thicknesses influenced by jet dynamics and fiber bridging. Tensile testing shows nylon-12 tubes are notably stronger than poly(ε-caprolactone) ones and while annealing has limited impact on tensile strength, yield, and elastic modulus, it dramatically reduces elongation. The equipment described and material used broadens MEW applications for high melting point polymers and highlights the importance of cooling dynamics for reproducible samples.