Hierarchical Porous Ceramics with Distinctive Microstructures by Emulsion-Based Direct Ink Writing

Abstract

Hierarchical porous materials are ubiquitous in nature and have inspired the fabrication of cellular structures for a multitude of applications. As an extrusion-based 3D printing technique, direct ink writing (DIW) allows for customizable design and accurate control of printed structures. Recently, its combination with colloidal processing methods used for bulk porous ceramics, such as emulsion templating, has further extended its capability of fabricating porous ceramics across multiple length scales. In light of the recent development, the ink formulation for emulsion-based DIW can be further explored, and there is still a need for a better understanding of the structure–property relationship. Herein, we introduce two types of gelling additives, i.e., poly­(ethylenimine) (PEI) and Pluronic F-127, respectively, into particle-stabilized emulsions and fabricate hierarchical porous alumina lattices by DIW. We discover that the two gelling additives can lead to distinctive microstructures due to their different gelling mechanisms. Moreover, the 3D printed hierarchical porous ceramic lattices are found to exhibit a potential energy absorption property. The effects of ink formulations, including gelling additives and solid loading, on ink rheology, microstructure, and mechanical properties are investigated. The 3D printed hierarchical porous ceramic lattices exhibit a high average porosity of 73.7%–79.3% with an average compressive strength of 1.53–9.61 MPa and a specific energy absorption of 0.33–2.67 J/g. Featuring two distinctive microstructures with tunable structural features and mechanical properties, the 3D printed hierarchical porous ceramics in this study have potential in many applications, including lightweight structures, tissue engineering scaffolds, filtration, etc.

Review on Porous Scaffolds Generation Process: A Tissue Engineering Approach

“…This can be observed in Figure g, where they designed a sphere with micropores, however, the size, shape, and position of the pores depended on the salt-leaching process employed. This is similar to the example in Figure h and i, where the scaffold was designed at a macro scale, with the stacking of cylindrical fibers in a square manner, controlling the separation between them, but the microporosity of interest depended on the sintered fabrication and the separation of two-phase materials . In Figure j, an example is observed where the internal porosity was the result of the random deposition of fibers with electrospinning …”

“…This is similar to the example in Figure 4h and i, where the scaffold was designed at a macro scale, with the stacking of cylindrical fibers in a square manner, controlling the separation between them, but the microporosity of interest depended on the sintered fabrication and the separation of two-phase materials. 50 In Figure 4j, an example is observed where the internal porosity was the result of the random deposition of fibers with electrospinning. 51 Design is then an important part of the fabrication of the complete porous scaffold.…”

“…(h, i) Ceramic scaffold fabricated via emulsion-based direct ink writing. Reproduced from ref . Copyright 2022 American Chemical Society.…”

3D Printed Silicones with Shape Morphing and Low-Temperature Ultraelasticity

“…The rising three-dimensional (3D) printing technique, with its unparalleled freedom to create complex, customized geometries with low cost, shows great promise in controlling the internal morphologies and architectures of cellular materials. − Especially, 3D printing of silicones could be realized using direct ink writing (DIW), ,,,− inkjet printing, , embedded 3D printing, , vat polymerization, , and expanded techniques for higher resolution. , Mechanical responses of the printed foams could be well predicted, designed, and/or optimized by digital techniques such as simulation and machine learning , and further tailored by controlling the inner structure (such as the polymer network , and filler orientation , ) of the printed filaments. In addition, by introducing micro- or nanoscale pores in the 3D printed filaments using a sacrificial templating concept, − a hierarchical porous structure could be achieved, endowing the foam with ultraelasticity (i.e., extreme compressibility and cyclic endurance) and much enhanced active surface area compared to its nonhierarchical counterparts, , which is favorable for high-tech fields such as aerospace, energy, and bioengineering.…”

Prestrain Programmable 4D Printing of Nanoceramic Composites with Bioinspired Microstructure

“…[11][12][13] Natural structures have brought about numerous inspirations for advanced materials with unprecedented properties due to their unique hierarchical structures. [14][15][16] Among them, the concentric cylinder structure is ubiquitous in biological systems such as scallion, [17] the tracheid of wood, [18] the spicule of Euplectella aspergillum [19] and the bone haversian system [20] due to their unique growth organism. Such structure plays a significant role in improving the strength, toughness and flexibility of the materials via increasing the fracture path and energy absorption.…”