Periodic Reporting for period 1 - 3D-Carbon (3D Printing of Pyrolytic and Graphitic Carbon)
Reporting period: 2023-09-01 to 2025-08-31
3D printed carbon materials hold great promise for bone tissue engineering due to their cytocompatibility, mechanical strength, and electrical conductivity. However, current additive manufacturing strategies for carbon are limited primarily to ink-based printing methods using graphene or carbon nanotubes dispersed in polymeric matrices. While such composites provide some level of functionality, the polymer host compromises carbon purity, structural stability, and reproducibility, thereby restricting their performance and long-term application. Pyrolytic carbon, produced through the thermal conversion of polymers, offers a route to fabricate pure, highly stable carbon structures with tunable micro- and nano-architectures. Nevertheless, the use of 3D printed pyrolytic carbon (3DPyC) in tissue engineering remains almost unexplored. Challenges persist in achieving high graphitization, ensuring reproducibility, and maintaining control over mechanical and surface properties. Furthermore, the reliance on commercial photoresins of undisclosed chemical composition has limited mechanistic understanding and hindered systematic optimization of scaffold properties.
The 3D-Carbon project aimed to overcome these challenges with three main objectives: (1) to introduce and systematically study a chemically well-defined precursor resin to enable controlled 3D printing of pyrolytic carbon (3DPyC) with tunable microstructural and material properties; (2) to develop an effective pathway to fabricate 3D printed highly graphitic carbon (3DGC) materials; and (3) to investigate the interactions between cells and 3D printed carbon lattices, evaluating their cytocompatibility and suitability for bone tissue engineering applications.
Achieving these objectives provides a reproducible and scalable approach for fabricating high-performance carbon scaffolds with precise control over structure and functionality. The project’s outcomes align with EU strategic priorities in advanced manufacturing and regenerative medicine, laying the groundwork for innovative bioelectronic implants and personalized tissue engineering solutions with broad clinical and industrial relevance.
The 3D-Carbon project aimed to overcome these challenges with three main objectives: (1) to introduce and systematically study a chemically well-defined precursor resin to enable controlled 3D printing of pyrolytic carbon (3DPyC) with tunable microstructural and material properties; (2) to develop an effective pathway to fabricate 3D printed highly graphitic carbon (3DGC) materials; and (3) to investigate the interactions between cells and 3D printed carbon lattices, evaluating their cytocompatibility and suitability for bone tissue engineering applications.
Achieving these objectives provides a reproducible and scalable approach for fabricating high-performance carbon scaffolds with precise control over structure and functionality. The project’s outcomes align with EU strategic priorities in advanced manufacturing and regenerative medicine, laying the groundwork for innovative bioelectronic implants and personalized tissue engineering solutions with broad clinical and industrial relevance.
The project began with the identification and validation of polyethylene glycol diacrylate (PEGDA) as a chemically well-defined resin precursor for the fabrication of 3D printed pyrolytic carbon (3DPyC). PEGDA offered excellent printability using digital light processing (DLP) 3D printing, allowing the fabrication of high-resolution lattice structures down to 200 µm features. Its known chemistry enabled systematic investigation of the carbonization mechanism, in contrast to commercial resins with proprietary formulations.
A comprehensive study of the carbonization pathway of PEGDA was performed, combining thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Samples pyrolyzed at different temperatures (410-900°C) were analyzed to elucidate structural transformation, reaching a shrinkage up to ~89% and a strut diameter down to ~23 µm. The higher carbonization temperature also led to a progressive increase in sp2 carbon domain, demonstrating a transformation from highly amorphous carbon at 410°C to turbostratic carbon at 900°C. This transformation also resulted in a substantial increase in mechanical properties and electrical conductivity with increasing pyrolysis temperature. This work established a clear correlation between precursor chemistry, processing parameters, and the resulting carbon microstructure.
Building on this foundation, to achieve 3D printed graphitic carbon (3DGC), the project incorporated metal-organic frameworks (MOFs) within PEGDA by innovating an in situ MOF growth process within 3D printed PEGDA microlattices. Cobalt and nickel-based zeolite MOFs, ZIF67 and Ni-ZIF, respectively, were of particular focus due to the catalytic effect of Co and Ni. Carbonization of these MOF/PEGDA structures resulted in highly graphitized 3D carbon architectures, as evidenced by Raman spectroscopy and X-ray diffraction. Interestingly, Ni-ZIF/PEGDA structures led to in situ conformal growth of carbon nanotubes (CNTs) on the 3D printed carbon lattice, providing a breakthrough in 3D growth of CNTs.
In parallel, cytocompatibility studies were performed with MC3T3-E1 pre-osteoblast cells to check the efficacy of these 3D printed carbon structures in bone tissue engineering. The 3DPyC scaffolds demonstrated excellent cell attachment, spreading, proliferation, and osteogenic differentiation. However, MOF/PEGDA-derived 3DGC did not show any convincing cell-material interaction, probably due to the highly porous nature of the CNT forest on its surface.
Key achievements include: (1) Establishment of PEGDA as a reproducible and chemically defined resin precursor for 3DPyC, (2) Comprehensive understanding of PEGDA carbonization and its impact on material properties, (3) Development of a novel MOF-PEGDA strategy, showing in situ MOF growth within printed PEGDA structures, (3) Conformal in situ growth of CNTs on printed carbon lattices through carbonization of Ni-ZIF/PEGDA composite lattices, and (5) Demonstration of cytocompatibility of 3D printed carbon scaffolds for bone tissue engineering.
A comprehensive study of the carbonization pathway of PEGDA was performed, combining thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Samples pyrolyzed at different temperatures (410-900°C) were analyzed to elucidate structural transformation, reaching a shrinkage up to ~89% and a strut diameter down to ~23 µm. The higher carbonization temperature also led to a progressive increase in sp2 carbon domain, demonstrating a transformation from highly amorphous carbon at 410°C to turbostratic carbon at 900°C. This transformation also resulted in a substantial increase in mechanical properties and electrical conductivity with increasing pyrolysis temperature. This work established a clear correlation between precursor chemistry, processing parameters, and the resulting carbon microstructure.
Building on this foundation, to achieve 3D printed graphitic carbon (3DGC), the project incorporated metal-organic frameworks (MOFs) within PEGDA by innovating an in situ MOF growth process within 3D printed PEGDA microlattices. Cobalt and nickel-based zeolite MOFs, ZIF67 and Ni-ZIF, respectively, were of particular focus due to the catalytic effect of Co and Ni. Carbonization of these MOF/PEGDA structures resulted in highly graphitized 3D carbon architectures, as evidenced by Raman spectroscopy and X-ray diffraction. Interestingly, Ni-ZIF/PEGDA structures led to in situ conformal growth of carbon nanotubes (CNTs) on the 3D printed carbon lattice, providing a breakthrough in 3D growth of CNTs.
In parallel, cytocompatibility studies were performed with MC3T3-E1 pre-osteoblast cells to check the efficacy of these 3D printed carbon structures in bone tissue engineering. The 3DPyC scaffolds demonstrated excellent cell attachment, spreading, proliferation, and osteogenic differentiation. However, MOF/PEGDA-derived 3DGC did not show any convincing cell-material interaction, probably due to the highly porous nature of the CNT forest on its surface.
Key achievements include: (1) Establishment of PEGDA as a reproducible and chemically defined resin precursor for 3DPyC, (2) Comprehensive understanding of PEGDA carbonization and its impact on material properties, (3) Development of a novel MOF-PEGDA strategy, showing in situ MOF growth within printed PEGDA structures, (3) Conformal in situ growth of CNTs on printed carbon lattices through carbonization of Ni-ZIF/PEGDA composite lattices, and (5) Demonstration of cytocompatibility of 3D printed carbon scaffolds for bone tissue engineering.
The 3D-CARBON project delivered advances that extend well beyond the state of the art in both additive manufacturing and regenerative medicine. First, the introduction of PEGDA as a model resin for pyrolytic carbon 3D printing establishes the first reproducible, chemistry-controlled platform for investigating carbonization mechanisms in printed architectures. This overcomes the major limitation of prior studies that relied on commercial, undisclosed resin formulations.
Second, the development of hybrid MOF-PEGDA systems represents a unique pathway to achieving 3D printed highly graphitic carbon structures. The in situ growth of CNTs directly within the printed lattices is unprecedented, providing new opportunities to design multifunctional scaffolds with tailored electrical, mechanical, and surface properties. This innovation not only enhances the performance of 3D printed carbon but also opens routes for functionalization toward sensing, catalysis, and energy applications.
Third, the biological validation of 3DPyC scaffolds marks the first demonstration of their cytocompatibility and potential for bone tissue engineering. The findings highlight the ability of carbon micro- and nanostructures to support cell attachment and proliferation while offering conductivity for future stimulation-based therapies. This positions 3D printed carbon as a promising new class of biomaterials bridging structural performance with bioelectronic functionality.
In summary, 3D-CARBON provides a reproducible methodology for fabricating tunable carbon architectures, introduces a breakthrough strategy for graphitization through MOF-derived CNT growth, and demonstrates the feasibility of carbon scaffolds in regenerative medicine. These outcomes go beyond current technologies by uniting high-resolution 3D printing, controlled carbon chemistry, and biological validation, thus laying the scientific foundation for next-generation implantable devices and multifunctional biomaterials.
Second, the development of hybrid MOF-PEGDA systems represents a unique pathway to achieving 3D printed highly graphitic carbon structures. The in situ growth of CNTs directly within the printed lattices is unprecedented, providing new opportunities to design multifunctional scaffolds with tailored electrical, mechanical, and surface properties. This innovation not only enhances the performance of 3D printed carbon but also opens routes for functionalization toward sensing, catalysis, and energy applications.
Third, the biological validation of 3DPyC scaffolds marks the first demonstration of their cytocompatibility and potential for bone tissue engineering. The findings highlight the ability of carbon micro- and nanostructures to support cell attachment and proliferation while offering conductivity for future stimulation-based therapies. This positions 3D printed carbon as a promising new class of biomaterials bridging structural performance with bioelectronic functionality.
In summary, 3D-CARBON provides a reproducible methodology for fabricating tunable carbon architectures, introduces a breakthrough strategy for graphitization through MOF-derived CNT growth, and demonstrates the feasibility of carbon scaffolds in regenerative medicine. These outcomes go beyond current technologies by uniting high-resolution 3D printing, controlled carbon chemistry, and biological validation, thus laying the scientific foundation for next-generation implantable devices and multifunctional biomaterials.