Tian Li
Email Address
litian@nus.edu.sg
Organizational Units
ENGINEERING
faculty
COLLEGE OF DESIGN & ENG
faculty
2 results
Publication Search Results
Now showing 1 - 2 of 2
Publication Controlling the hierarchical microstructure of bioceramic scaffolds by 3D printing of emulsion inks(ELSEVIER, 2023-01-05) Liu, Quyang; Li, Tian; Gan, Soo Wah; Chang, Soon Yee; Yen, Ching Chiuan; Zhai, Wei; Dr Wei Zhai; DIVISION OF INDUSTRIAL DESIGN; MECHANICAL ENGINEERINGMechanical and biological properties constitute the most fundamental requirements for bone tissue engineering (BTE) scaffolds. Nonetheless, existing fabrication strategies find it difficult to prepare highly porous BTE scaffolds for improved biological properties while also preserving sufficient mechanical properties that are compatible with the natural bone. Inspired by the hierarchical porous materials in Nature, hierarchical porous BTE scaffolds can achieve a combination of superior mechanical efficiency and biological functions. With this in mind, this study reports the fabrication of hierarchical porous hydroxyapatite (hpHA) scaffolds by 3D printing of emulsion inks. The scaffolds exhibit high porosity up to 73.7%, featuring 3D printed macropores of 300 – 400 µm and emulsion templated microporosity of < 20 µm. Via formulation of the emulsion inks, such as varying the oil volume and adding Pluronic® F-127, this process demonstrates effective control of the microporosity and pore morphology of the scaffolds. The scaffolds are mechanically compatible with the natural cancellous bone, with compressive strength in the range of 1.41 – 7.84 MPa and Young's modulus of 57.3 – 304 MPa. Furthermore, the elastic admissible strain (EAS) and specific energy absorption (SEA) of the hpHA scaffolds can be increased up to 4.4% and 1.22 kJ/kg, respectively, indicating greatly enhanced mechanical performances owing to the hierarchical porous structure. Meanwhile, improved cell attachment, spreading and proliferation are observed in these scaffolds with their additional microporosity. Hence, the hpHA scaffolds in this study show great potential in BTE applications, and the reported process of 3D printing of emulsion inks is a promising fabrication strategy for further optimization of highly porous BTE scaffolds.Publication Prestrain Programmable 4D Printing of Nanoceramic Composites with Bioinspired Microstructure(Wiley, 2022-11-24) Li, T; Liu, Q; Qi, H; Zhai, W; Dr Wei Zhai; MECHANICAL ENGINEERINGFour-dimensional (4D) printing enables programmable, predictable, and precise shape change of responsive materials to achieve desirable behaviors beyond conventional three-dimensional (3D) printing. However, applying 4D printing to ceramics remains challenging due to their intrinsic brittleness and inadequate stimuli-responsive ability. Here, this work proposes a conceptional combination of bioinspired microstructure design and a programmable prestrain approach for 4D printing of nanoceramics. To overcome the flexibility limitation, the bioinspired concentric cylinder structure in the struts of 3D printed lattices are replicated to develop origami nanoceramic composites with high inorganic content (95 wt%). Furthermore, 4D printing is achieved by applying a programmed prestrain to the printed lattices, enabling the desired deformation when the prestrain is released. Due to the bioinspired concentric cylinder microstructures, the printed flexible nanoceramic composites exhibit superior mechanical performance and anisotropic thermal management capability. Further, by introducing oxygen vacancies to the ceramic nanosheets, conductive nanoceramic composites are prepared with a unique sensing capability for various sensing applications. Hence, this research breaks through the limitation of ceramics in 4D printing and achieves high-performance shape morphing materials for applications under extreme conditions, such as space exploration and high-temperature systems.