Continuous 3D Printing of Hierarchically Structured Microfoamed Objects

We report the design and results of a novel process combining 3D printing and foaming to produce microfoamed polymeric structures, from simple strands to more complex architectures, using physical blowing agents. Foaming processes are extensively operated in polymeric cellular materials industry to produce pores, yet without spatial control of their positioning. This intrinsic stochasticity may introduce imperfections, which reduce the mechanical properties of the material, thus regular (e.g., periodic) porous structures would be more desirable. 3D printing allows to fabricate polymeric cellular materials with empty spaces in a well‐defined periodic structure. To this end, very expensive 3D printers are required to achieve micron‐resolution pores. Correspondingly, the production time is dramatically large and becomes a bottleneck to the industrial scale‐up. Herein, an innovative technique combining the simplicity of polymer foaming with the precision of 3D printing is presented. The resulting materials have the advantages of both the techniques: they have a micron‐controlled cell structure and can be printed at reasonable costs and time. The proposed approach is validated using a bio‐based and compostable polymer, namely, polylactic acid (PLA). The resulting foamed strands and hierarchical structures are novel in terms of morphology and show a controlled local porosity and superior mechanical properties.