Highly porous hollow 3D devices obtained by a combined melt-wet processing for long-term controlled release

The possibility to obtain resistant and reusable hollow devices with differentiated high porosity for storage and tunable long-term controlled release of substances is difficult to achieve efficiently. To solve this problem, we propose a combined melt-wet processing, which allows predictable and tunable morphologies. The process consists in combining Material Extrusion (MEX) with an eco-friendly salt leaching in distilled water, by using a biostable polymer and high percentages of saline porogen. Three blends with PA6/NaCl-30/70wt% composition were extruded, varying the salt particles size, that shows good dispersion in all the filaments, with a spontaneous tendency for bigger particles to accumulate in the central region of the cross-sections, attributable to fluid-dynamic reasons. Blends rheological and mechanical properties appeared suitable for the printing process. The hollow devices were then printed and successfully leached, resulting in homogeneously dispersed pores, with size ranges comparable to those of the porogen for each blend; therefore, the morphology of the pores can be directly predicted by the porogen and it was not altered during processing. Leaching occurred completely, in fact the real porosity for each device was consistent with the theoretical one. Despite the high percentage of voids, the hollow devices appeared to be mechanically resistant and therefore suitable for the application. Controlled release up to 11 days of a model molecule (methylene blue) was tested and predictable kinetics related to pore size were achieved so, therefore, they are easily tunable and versatile. Release data were fitted according to Peppas-Korsmeyer-model to describe the release mechanism related to porosity.