The production of 3D printed safety protection devices (SPD) requires particular attention to the material selection and to the evaluation of mechanical resistance, biological safety and surface roughness related to the accumulation of bacteria and viruses. We explored the possibility to adopt additive manufacturing technologies for the production of respirator masks, responding to the sudden demand of SPDs caused by the emergency scenario of the pandemic spread of SARS-COV-2. In this study, we developed different prototypes of masks, exclusively applying basic additive manufacturing technologies like fused deposition modeling (FDM) and droplet-based precision extrusion deposition (db-PED) to common food packaging materials. We analyzed the resulting mechanical characteristics, biological safety (cell adhesion and viability), surface roughness and resistance to dissolution, before and after the cleaning and disinfection phases. We showed that masks 3D printed with home-grade printing equipment have similar performances compared to the industrial-grade ones, and furthermore we obtained a perfect face fit by customizing their shape. Finally, we developed novel approaches to the additive manufacturing post-processing phases essential to assure human safety in the production of 3D printed custom medical devices.

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Fused Deposition Modelling (FDM) is one of the most widespread additive manufacturing technologies due to its relatively low cost and simplicity. Usually, printed parts have an internal structure (infill) that is not produced with 100% material density. This strategy is adopted to save material and time thanks also to the fact that when a component is loaded, stress are concentrated on its skin rather than in the internal section. Furthermore, infill structure can have different densities and topology. Slicer software have various configurations that can be exploited to produce internal structures: according to All3DP [1], some are intended for functional parts while others are more indicated to prototypes only. Aim of this work, is to compare the effect of different infill topologies produced using Ultimaker CURA [2] slicing software on material mechanical properties. Preliminary experimental activity has been carried out in order to determine the most suitable printing temperature. MaCh3D, an innovative miniaturized universal testing machine [3] was used to perform uniaxial tensile tests. Results underline the difference between different kind of infill in term of mechanical properties, given the same infill density across all specimens. Additionally, in order to evaluate infill percentage effect on mechanical properties, some of the most performing infill from the characterisation activity have been selected and specimens produced with 20%, 50%, 80% infill percentage. In the end, both infill topology as well as density impacts on mechanical properties.

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