Controlled In Situ Foaming for Mechanical Responsiveness of Architected Foams

Addition of chemical blowing agents to polysiloxane resins produces foams with closed-cell morphology. Combining this chemistry with the 3D-printing technique direct ink writing (DIW) permits the creation of architected foams with controllable, hierarchical tiers of porosity. Using a two-component foaming ink, the extent of foaming can be controlled by incorporating an active mixing printhead as part of the fabrication process. Changes in the mixing speed allows for in situ control of the foaming reaction where the mixing speed is directly correlated with the resulting foaming that occurs upon extrusion. These architected foams display tunable mechanical responses, porosities, and open-to-closed cell ratios. While chemically blown polysiloxane foam is a well-established material, utilizing DIW as fabrication technique presents a novel approach for creating tailored, architected foams that require minimal post-processing. An in-line mixing printheads and 3D-printing platform are combined to create structures made up of siloxane-based hydrogen-blown foam. The effect of mixing on the foam formation is investigated, and structures with local composition variation are fabricated. This process is used to tune the degree of foaming and location of the foam, influencing the mechanical response of the structure.image (c) 2023 WILEY-VCH GmbH