image: Nichoids patterned in a (a) 200-µm side triangle; (b) 300-µm side hexagonal layout. Elementary nichoids patterned in a (c) 200-µm side triangle; and (d) 300 µm side hexagonal layout. view more
Credit: by Xiaobo Li, Wanping Lu, Xiayi Xu, Yintao Wang, Shih-Chi Chen
Tissue engineering (TE) is a process of generating tissue by adding combinations of appropriate cells and materials onto specific scaffolds. However, most normal tissue-derived cells are anchorage-dependent and reside in extracellular matrices (ECMs). Ideally, the best 3D scaffold for a given engineered tissue should be the corresponding ECM in its native state. Nevertheless, native ECMs are functionally diversified with complex composition, and naturally dynamic, making it extremely challenging to mimic such structures in vitro. Therefore, a thorough investigation into scaffold fabrication is critical to enhance TE development.
Thanks to the leaping progress in 3D printing technology, the fabrication of customized scaffolds with controlled structure and scale is now a reality. Moreover, advanced optical 3D printing methods have enabled the printing of the fixture of cells, growth factors, and multiple biocompatible materials altogether onto the complex 3D scaffolds that possess a high degree of structural and functional similarities to native ECMs.
In a new paper published in Light: Advanced Manufacturing, a team of scientists, led by Professor Shih-Chi Chen from the Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China, has provided a comprehensive and up-to-date review of current optical 3D printing methods for scaffold fabrication, including the material extrusion and jetting-based processes, selective laser sintering (SLS), stereolithography (SLA), two-photon polymerization (TPP), and volumetric fabrication. Specifically, the team reviews the optical design, materials, and representative applications, followed by a fabrication performance comparison. Important metrics include fabrication precision, rate, materials, and application scenarios. Summaries and comparisons of each technique are provided to guide the readers in the optics and TE communities to select the most fitting printing approach under different application scenarios.
The authors stated that “optical 3D printing methods are extremely effective due to their superior performance, cost-effectiveness, and the prospect of broader applications with emerging breakthroughs in new materials that address the fast-growing demand in 3D scaffold fabrication in TE.”
“In fact, we recognize a positive interplay among scaffold applications, materials and 3D printing methods. In other words, the demand for advanced scaffold has been the driving force for the development in material and 3D printing methods and vice versa.” they added.
“The fabrication of large-scale 3D scaffolds remains quite challenging, as optical 3D printing methods, especially TPP, achieves a much higher resolution (up to hundred nanometers) at the expense of printing time and ultimately the scaffold's final size. The FP-TPL technique recently developed by our team is capable of printing 3D structures with the highest throughput (10–100 mm3/h) and resolution (140/175 nm in the lateral/axial directions) ever reported and a 90% cost reduction (~US$ 1.5 /mm3) comparing with current commercial solutions, which may address the long-standing challenges in high-resolution large-scale scaffold fabrication.” the authors forecast.
Journal
Light: Advanced Manufacturing