Freeform Polymer Precipitation in Microparticulate Gels

Embedded 3D printing has demonstrated fabricating freeform structures of curable polymer resins in microparticulate hydrogels. This method is, however, not compatible with thermoplastics extruded at high temperature. This communication presents a unique approach to 3D-print thermoplastics in embedding media, termed freeform polymer precipitation (FPP). FPP is based on spatially controlled immersion precipitation of polymer inks patterned in microparticulate gels for various thermoplastics with additives. The embedding media offer unique dual functions: Bingham plastic to maintain printed structures and nonsolvent for in situ precipitation of polymer inks. Polymer inks with a wide range of vapor pressure (0.04–60 kPa) and viscosity (0.1–1000 Pa·s) were demonstrated for FPP. Using acrylonitrile butadiene styrene dissolved in acetone (20–60 w/w %) as a model ink, we identified the printing conditions to ensure vertical and lateral attachments of printed inks. The fabricated 3D objects were porous because of rapid phase separation due to the nonsolvent, which was controlled by the concentration of the polymer and the porogens in the inks. FPP offers a simple route to fabricate 3D freeform structures of thermoplastics with controlled internal porosity and should serve as a useful toolkit to 3D-print multi-functional materials such as polymer nanocomposites.