The Agency for Science, Technology and Research's (A*STAR) Institute of Bioengineering and Bioimaging (IBB) and Institute of Molecular Cell Biology (IMCB) have developed a Fluid-supported Liquid Interface Polymerization (FLIP) 3D printer which can rapidly print hydrogel structures with complex geometry, while addressing the key nutrient supply issue in bioprinting.
Hydrogels are used in many biomedical applications, including regenerative medicine and surgical training phantoms. However, the ability to shape hydrogels into complex anatomical structures using additive manufacturing can be challenging due to their low mechanical stiffness.
Using the FLIP 3D printer, a buoyancy-assisted continuous digital light processing (DLP) 3D printing method, the patterns are projected directly onto a thin layer of fluid-supported hydrogel precursor, which serves as a floating liquid projection screen. After printing, the support fluid can be easily removed by rinsing. This approach prevents adhesion of the printed structure to the patterning window (e.g. LCD screens in typical resin-based 3D printers), thus eliminating an additional lifting step between layers that slows down the process.
As a result, FLIP can achieve a faster printing speed compared tothe conventional DLP, and routinely prints at a speed of 200mm/h along the vertical axis for stiffer hydrogels. The continuous printing also helps to improve the smoothness of the printed surfaces, which allows for the end product to be free of layering artifacts.
With an eye on bioprinting applications, A*STAR researchers have devised a strategy to incorporate a second, sacrificial ink, which when removed, creates channels that are able to supply the cells with nutrients, successfully keeping them alive in centimeter-scale printed structures.
Speaking about this work, Dr Cyrus Beh, Principal Investigator, IBB, and Senior Scientist at the Molecular Engineering Laboratory of IMCB, said, "We embarked on this project to address the challenges faced by conventional, extrusion-based bioprinters. The method was designed from the outset to be mild and compatible with cell printing. And while rapid fabrication with soft hydrogels is exciting, the most important aspect of this work is the ability to introduce nutrient supply channels, which will go a long way towards making tissue bioprinting a reality."
The team demonstrated the printer's capabilities by 3D printing various models such as the model of Marina Bay Sands (above), as well as fabricating spanning features out of hydrogels as soft as ~7 kPa. They are currently investigating long-term culturing and differentiation of bioprinted cells, as a way to create viable tissues for regenerative medicine purposes.
More information on the study, "A fluid-supported 3D hydrogel bioprinting method", can be found via the team's published paper in Biomaterials: https://www.sciencedirect.com/science/article/pii/S0142961221003902