Speaker
Description
Introduction
Robotic additive manufacturing (RAM) is currently being explored to overcome the limitations of layer-by-layer additive manufacturing technologies in the fabrication of complex constructs for regenerative medicine (RM). A few successful attempts at using RAM for in-situ extrusion-based bioprinting have been reported, where the fabrication is non-planar but still layer-by-layer1,2,3. Alternatively, light based volumetric bioprinting has increasingly been adopted for the generation of complex biological constructs, but it is limited by the narrow selection of biocompatible bioinks and inability to recapitulate anisotropic fiber orientations. Meanwhile, efficient methods to generate volumetric print paths/designs with anisotropic 3D geometries for RAM remains elusive, reducing the effectiveness of RAM for RM. Here, we explore the use of a simple continuous fiber scaffold designs which better utilize the volumetric printing capabilities of RAM as a strategy to fabricate 3D scaffolds for RM.
Methods
Designs
3D space filling curves could be used for efficiently generating volumetric scaffold geometries. However, these designs are impossible to be printed in small scales using extrusion-based 3D printers. Even when using RAM they require the robot to achieve complex orientations and current hardware limitations of industrial robots prevent the printing of these structures. Some simplified versions of space filling curves were chosen for the study.(Hilbert curve and Z-order (Morton) curve). A custom path optimization software was used to calculate the extruder orientation, thus preventing collisions while minimizing changes in orientation of the extruder during the printing. After testing the printability of these designs, larger scaffolds were generated by stacking the repeating units of the curves.
RAM
The RAM system used here couples a 7 degree of freedom robot (Xarm7) with a thermoplastic extruder. The integration of the robot and extruder was handled by an updated version of RAVEN4, which is an open-source RAM package developed in house based on ROS2 (Robot Operating System).
Printing tests
All the printing tests were done using polylactic acid (PLA) on a 0.4mm nozzle at a printing temperature of 180°C. After checking the paths for collisions (in simulation), the effect of print-speed, extruder orientation, cooling fan speed and segment length was studied by printing single unit-cells of each design. The best parameters were used for printing the larger scaffolds using the RAM and a 3-axis printer for comparison.
Results and Discussions
By replacing the fundamental units from layers to complex curves, we are able to achieve extrusion-based volumetric scaffolds while keeping the design process relatively simple. This approach opens new exciting opportunities for RM in terms of biomimicry and advanced devices for stimuli-responsive applications. Results from this study could become the steppingstone for future studies in fabrication of scaffolds with more complex architectures for RM using RAM.
References
1) Fortunato, G. M. et al. Bioprinting 28, (2022).
2) Armstrong, C. D. et al. Advanced Intelligent Systems 6, (2024).
3) Jeong, S. H. et al. Adv Mater Technol 9, (2024).
4) Fucile, P., David, V. C. et al. Virtual Phys Prototyp 19, (2024).
74734116326
