Hierarchical porous materials, characterised by their multi-level pore architectures, are crucial in diverse scientific fields such as catalysis and biomedical engineering. [1] The complexity of these structures requires precise control over porosity, mechanical integrity, and functionality. Sodium silicate solution, commonly known as water glass (WG), is increasingly preferred due to its unique properties and versatility. [2]

To produce structures with hierarchical porosity, we employed different processing methods, which expel water from the sodium silicate solution on different pathways . Notably, microwave processing emerged as a rapid and efficient method to create large-scale, highly porous glass foams within minutes, offering adjustable porosity and density. [3] Additionally, combining robocasting with WG’s foaming capabilities allowed for ambient temperature gelation, facilitating the fabrication of 3D porous structures that effectively integrate macro and microscale porosities. This method highlighted its environmental sustainability and cost-effectiveness. [4] Freeze-casting with WG also demonstrated the ability to produce uniform porous foams without morphological gradients along the freeze direction.

Our comprehensive evaluation involved optical and scanning electron microscopies and micro-computed tomography, confirming diverse porous architectures that span several magnitudes and establishing complex systems with hierarchical porosity. The compression tests confirmed their porosity-dependent mechanical properties. Initial characterisations using X-ray diffraction and degradation analyses in simulated body fluids suggest promising applications for WG as biomedical scaffolds.

Ultimately, WG not only serves as a base material but significantly enhances the fabrication process of hierarchical structures, promising substantial advancements in applications from biomedical scaffolds and beyond.

References

[1] X-Y. Yang; L-H. Chen; Y. Li; JC. Rooke, C. Sanchez; B-L. Su Chemical Society Reviews, 2017,46,481-558

[2] I. Halasz; M. Agarwal; R. Li; N. Miller Catalysis Today. 2007, 126, 196-202.

[3] L. Yang; A. Haibel; O. Görke; C. Fleck Materials & Design, 2022, 222, 111100.

[4] L. Yang; O. Kaba; P. Wang; D. Auhl; A. Haibe; O. Görke; C. Fleck Advanced Functional Materials, 2023, 2305927.