A study led by the School of Engineering of the Hong Kong University of Science and Technology (HKUST) has developed an modern method that overcomes the restrictions of traditional additive manufacturing (3D printing), significantly simplifying and accelerating the production of geometrically complex cellular ceramics. This groundbreaking approach has the potential to revolutionize the design and processing of multifarious ceramic materials, opening up latest possibilities for brand spanking new applications in energy, electronics, and biomedicine, including robotics, solar cells, sensors, battery electrodes, and bactericidal devices.
Cellular ceramics are widely used ceramic materials known for his or her stable performance, erosion resistance, and long service life. A research team led by Associate Professor YANG Zhengbao from the Department of Mechanical and Aerospace Engineering at HKUST designed a surface-tension-assisted two-step (STATS) processing technique to fabricate cellular ceramics with programmed 3D cell-based configurations. This approach involves two key steps: (1) the preparation of cell-based organic lattices assisted by the additive manufacturing method to construct the fundamental configurations, and (2) filling the precursor solution with the required constituent into the architected lattice.
One big challenge was controlling the liquid geometry. To handle this, the team utilized surface tension, a natural phenomenon, to capture the precursor solution in architected cellular lattices. By leveraging the flexibility of surface tension to trap and pin fluids in prepared lattices, they successfully controlled the liquid geometry and managed to fabricate cellular ceramics with high precision.
The team further investigated the geometry parameters for the architected lattices assembled by unit cells and unit columns, each theoretically and experimentally, to guide the 3D fluid interface creation in arranged configurations. After drying and high-temperature sintering, the architected cellular ceramics were obtained. Using the brand new STATS approach, the ingredient synthesis was separated from architecture constructing, enabling the programmable manufacturing of cellular ceramics with various cell sizes, geometries, densities, meta-structures, and constituent elements. With high programmability, the strategy is applicable to each structural ceramics (e.g. Al2O3) and functional ceramics (e.g. TiO2, BiFeO3, BaTiO3).
To confirm the prevalence of the strategy, researchers also studied the piezoelectric performance of cellular piezoceramics. They found that the proposed approach could decrease the micropores and improve the local compactness in sintered cellular ceramics due to the significantly reduced organic component within the feedstock. This process advantages the manufacturing of worldwide porous and locally compact cellular piezoceramics, achieving a comparatively high piezoelectric constant d33 (~ 200 pC N-1) even at a really high overall porosity (> 90%).
Prof. Yang revealed that the strategy was inspired by diatoms, that are algae commonly present in sediments or attached to solid substances in waters and serve directly and not directly as food for a lot of animals. Single-celled diatoms are distinctly characterised by their silica frustule, or external cell wall. Due to a genetically programmed biomineralization process, their frustules are constructed in highly precise structures that exhibit a wide range of morphology, shape, geometry, pore distribution, and assembly.
“Our strategy overcomes the restrictions of conventional manufacturing methods and enables the creation of programmable, geometrically complex ceramic architectures. This novel approach will help process quite a few structural and functional cellular ceramics, contributing to applications involving filters, sensors, actuators, robotics, battery electrodes, solar cells, and bactericidal devices. Furthermore, the philosophy of engineering fluid interface for solid fabrication also provides a brand new solution for combining interfacial processing with modern manufacturing, enlightening the synergistic development of advanced design and intelligent materials,” Prof. Yang elaborated.
