Architected cellular ceramics with tailored stiffness via direct foam writing

Abstract

Hierarchical cellular structures are ubiquitous in nature because of their low-density, high-specific properties, and multifunctionality. Inspired by these systems, we created lightweight ceramic architectures composed of closed-cell porous struts patterned in the form of hexagonal and triangular honeycombs by direct foam writing. The foam ink contains bubbles stabilized by attractive colloidal particles suspended in an aqueous solution. The printed and sintered ceramic foam honeycombs possess low relative density (∼6%). By tailoring their microstructure and geometry, we created honeycombs with different modes of deformation, exceptional specific stiffness, and stiffness values that span over an order of magnitude. This capability represents an important step toward the scalable fabrication of hierarchical porous materials for applications,

Hierarchical cellular scaffolds fabricated via direct foam writing using gelled colloidal particle‐stabilized foams as the ink

“…Digital photographs of honeycombs are illustrated in Figure 7A,B, showing that the honeycombs with various sizes and shapes can be obtained. 18 The crosses of the filaments manifested nearly seamless integration of printed filaments with porous microstructure (Figure 7D,E). Phase compositions of specimens determined by XRD indicated that magnesium aluminate spinel (MgAl 2 O 4 ) was the only crystalline phase as a consequence of chemical reaction between Al 2 O 3 and MgO.…”

“…Among these methods, direct ink writing (DIW) is an attractive and versatile 3D printing technology to construct multifunctional structures for the applications in various fields ranging from smart composites, 6,7 bioinspired materials, 8,9 and electron component. 17,18 This method was defined as "direct foam writing" (DFW). The inks usually possess similar rheological properties, that is, shear thinning and viscoelasticity, 12,13 to assistant the printing process.…”

“…10,11 During such printing process, viscoelastic inks are squeezed out of the nozzles to form filamentary struts and finally become various patterns according to the prescribed motion of nozzles. 18 However, most of the printing process are light-based, and their foam inks usually have intricate constituents which must hybrid with preceramic resins [19][20][21][22] or photopolymerizable organics [23][24][25][26] to facilitate gelation during printing. Nowadays various inks which span as diverse as hydrogels, 14 viscoelastic polymer, 15 and elastomers 16 have been successfully proposed for DIW method.…”

Closed porosity ceramics and glasses

“…Concurrent usage of AM with other methods (eg, emulsified wet foam 3D printing) provides design freedom so that not just sophisticated shapes (microarchitected truss structures) and precise control of the pore character becomes possible but also less defected structures and consequently enhanced strength is attainable. However, currently there are still problems such as low density and resolution, poor surface finish, flaws, and most importantly very high cost (of one‐pot printing devices) for small lot manufacturing.Wet foams synthesized by Muth et al were used to obtain predefined, bio‐inspired hierarchical architectures with mixed mode mechanical responses; in Figure A‐C, anode with multiple strut connectivity and inner microstructure is given. The manufactured components had bending‐dominated hexagonal or stretching‐dominated triangular trusses constituted by closed porosity (or nearly dense) imposing additional bending‐dominated response by altering the processing parameters (ink composition, geometry, dry and sintering).…”

“…(A) Printed and sintered component with triangular cells, and (B) the close magnification image of a node, and (C) the resulting SEM image showing the closed porosity microstructure of the node (Reproduced with permission from)…”