Study on filament deflection in lattice porous structures fabricated through direct ink writing

Direct ink writing (DIW) technology supersedes traditional mold-based forming methods, significantly enhancing the fabrication of personalized and customized products with complex structures. This technology particularly excels in achieving precise control over the porosity of porous constructs. This study employs inorganic Al₂O₃ as raw material, sodium hexametaphosphate as dispersing agent, and inorganic SiO₂ micropowder as binding medium to fabricate lattice porous structures. One challenge encountered is the viscoelastic behavior of the extruded filament. When spanning the unsupported segments of the lower layer, the upper extruded filaments are susceptible to deflection or collapse, adversely affecting the porosity and dimensional fidelity of the final specimens. Experimental results revealed that a larger span and smaller modulus will cause the extruded filament to be more prone to deformation at the midpoint. The introduction of 2 wt% polyethylene glycol as a plasticizer mitigates this issue, ensuring nondeflection of the extruded filaments at a span of 6 mm. The deflection model for the extruded filament about span and modulus identifies the minimum modulus necessary to prevent or minimize deflection under given spans, which closely approximates our experimental findings, offering a valuable framework for guiding the production of high-precision, porosity-controlled porous structures.