Design and Characterization of Microfoamed Strands By Continuous 3D Foam Printing

 We report the design and the results of a novel process that combines

3D printing and foaming to produce microfoamed polymeric structures, from

strands to more complex architectures, using physical blowing agents. In the

context of polymeric cellular materials, foaming processes, either using

physical or chemical blowing agents, are extensively operated in industry to

produce pores, yet without a spatial control of the pore positioning. This

intrinsic stochastic structuring may introduce imperfections, which reduce the

overall mechanical properties of the material; thus, regular (e.g., periodic)

structures are more desirable than stochastic ones. 3D printing is another

technique to fabricate polymeric cellular materials and it allows to produce

cellular materials with empty spaces in precise locations and with a

well-defined periodic structure. To this end, very expensive 3D printers are

required to achieve micron-resolution pores. Correspondingly, the production

time increases dramatically, and becomes a bottleneck to the industrial

scale-up. Herein, we present an innovative technique that combines the

simplicity of polymer foaming with the precision of 3D printing. The resulting

cellular materials have the advantages of both techniques: they have a micron-controlled

cell structure and can be printed at reasonable costs and time. The proposed

approach is validated using a biobased and compostable polymer for application

in biomedical, agriculture and chemical engineering fields. The resulting

foamed strands are novel in terms of morphology with a controlled local

porosity that opens up to an immense scenario of applications thanks to a

possible cost-effective production of hierarchical structures with superior

properties (e.g., scaffolds for bioengineering and advanced devices for energy

storage or collection).