Abstract
Although extrusion-based three-dimensional (EB-3D) printing technique has been widely used in the complex fabrication of bone tissue-engineered scaffolds, a natural bone-like radial-gradient scaffold by this processing method is of huge challenge and still unmet. Inspired by a typical fractal structure of Koch snowflake, for the first time, a fractal-like porous scaffold with a controllable hierarchical gradient in the radial direction is presented via fractal design and then implemented by EB-3D printing. This radial-gradient structure successfully mimics the radially gradual decrease in porosity of natural bone from cancellous bone to cortical bone. First, we create a design-to-fabrication workflow with embedding the graded data on basis of fractal design into digital processing to instruct the extrusion process of fractal-like scaffolds. Further, by a combination of suitable extruded inks, a series of bone-mimicking scaffolds with a 3-iteration fractal-like structure are fabricated to demonstrate their superiority, including radial porosity, mechanical property, and permeability. This study showcases a robust strategy to overcome the limitations of conventional EB-3D printers for the design and fabrication of functionally graded scaffolds, showing great potential in bone tissue engineering.
Highlights
The critical segmental bone defect is one of the main problems in orthopedics, which seriously affects patient’s health and quality of life [1]
We have developed a novel bone-mimicking radial-gradient scaffold based on a customized design-to-fabrication workflow, enabling us to obtain controllable radial-gradient structures by EB-3D printing, which solves the thorny problem of traditional EB-3D printing in preparing gradient structures. (Table S4, Supporting Information)
Our proposed work is capable of designing the bone-mimicking radialgradient scaffolds with any number of iterations, but due to the manufacturing accuracy of EB-3D printer, we only show the bone-mimicking scaffolds with 0 to 3 iterations in this article, and 3-iteration strategy can already achieve the bone-mimicking radial-gradient scaffolds with a gradual decrease in porosity along the radial direction
Summary
The critical segmental bone defect is one of the main problems in orthopedics, which seriously affects patient’s health and quality of life [1]. It is very challenging to design and fabricate functionally graded scaffolds that mimic natural bone structure based on EB-3D printing technology [20]. A design-to-fabrication workflow was developed to build a bridge between the parametric design of the CAD models and the EB-3D printing of the fractal-like scaffold. This workflow provides a viable possibility for extending the application scope of traditional EB-3D printing techniques to fabricate complex structures. The synergy of the fractal theory and design-to-fabrication workflow could shed light on more advanced porous scaffolds and functionally graded materials for bone tissue engineering
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