High-strength and multifunctional honeycomb polyimide aerogel fabricated by a freeze casting-assisted extrusion printing and building block-assembly strategy for sound absorbing metamaterials

The key issue of extrusion-based 3D printing of polyimide (PI) aerogels is the regulation of the ink rheology. Herein, a novel freeze casting-assisted extrusion printing method is proposed for the fabrication of honeycomb PI aerogels. Owing to the grid-like honeycomb structure with a periodic topological distribution, the compressive modulus of the honeycomb PI aerogel reached 63.5 MP at a density of 0.195 g & sdot;cm-3. Furthermore, the properties of the PI aerogels were synchronously regulated, e.g. the density (0.099-0.195 g & sdot;cm-3), the thermal conductivity (0.0382-0.0787 W & sdot;m-1 & sdot;K-1), and the compressive strength (3.15-6.35 MPa), by manipulating the ink viscosity and honeycomb porosity. On this basis, a building block-assembly strategy of the printed PI aerogels was developed by controlling the temperature field and the gel's self-healing behavior, and two types of PI aerogel metamaterials for acoustic absorption were fabricated. These metamaterials exhibited enhanced overall sound absorption performance, with a new absorption peak with a sound absorption coefficient of 0.86 at a lower frequency. The freeze casting-assisted extrusion printing method can be extended to all solidifiable sol inks, and the building block-assembly strategy is inspiring for the general 3D printing of multifunctional aerogel materials and acoustic metamaterials.

Automated summary

A novel freeze casting-assisted extrusion printing method is proposed for the fabrication of honeycomb polyimide (PI) aerogels, with properties of the aerogels synchronously regulated by manipulating the ink viscosity and honeycomb porosity. A building block-assembly strategy is developed to fabricate two types of PI aerogel metamaterials for acoustic absorption, exhibiting enhanced overall sound absorption performance.