Sustainable Photoluminescent Materials Based on Bio-Based Photocurable Functional Inks for Digital Light Processing

The increasing demand for additive manufacturing, particularly digital light processing (DLP) printing, has raised concerns regarding its environmental impact. Conventional materials used in DLP printing, such as petroleum-based resins, often pose challenges in terms of sustainability, resource depletion, and waste generation. To address these issues, it is required to explore sustainable alternatives derived from natural sources.<br/>Natural polymers have gained significant attention as potential ink materials due to their availability, low cost, biodegradability, and compatibility with various printing techniques. The formulation of natural polymer-based inks involves careful consideration of their rheological properties, stability, and printability, while maintaining biocompatibility and environmental sustainability. This work highlights the key factors influencing ink development, including material selection, ink formulation, and process parameters optimization, to achieve reliable and high-quality 3D printed objects. Thus, different reactive diluents have tested in soybean oil-based ink in order to optimize the ink viscosity with the aim to produce a completely DLP printable formulation. Furthermore, photopolymerization process of obtained materials denotes to be comparable with commercially available resins maintaining high biorenewable carbon content and presenting high quality in printing parts.<br/>Furthermore, the incorporation of fillers into natural polymer-based inks has opened up new possibilities for functionalizing printed objects. By incorporating photoluminescent materials into the ink formulation, printed objects have been fabricated that exhibit luminescent characteristics, making them suitable for applications such as signalling, identification, security features, or decorative elements.<br/>This work delves into the potential of photoluminescent salt fillers based on lanthanide ions as they possess several unique luminescent features of high technological interest: long luminescence lifetimes (μs to ms), fingerprint emission profiles, fine emission bands, and large pseudo-Stokes shifts. Thus, five photoluminescent salts are used, three of them that emit efficiently in the visible spectral region based on Eu³⁺ (red, 612 nm), Tb³⁺ (green, 544 nm) or Tm³⁺ (blue, 440 nm), and two more emitting in the near infrared spectral region, the Yb³⁺ (1000 nm) and the Nd³⁺ (808 nm). The impact of filler type and dispersion on the optical properties and overall performance of printed structures will be discussed, showing quantitative signal even at low concentration of 5 wt.%, together with a high quality of printing parts. In addition, the challenges associated with natural polymer-based ink development, such as achieving sufficient mechanical strength due to the negative impact of the addition of fillers into the polymer, optimizing print conditions ascribed to the light absorption of the fillers that difficult the photopolymerization process during printing, and ensuring good photoluminescent properties will be addressed.<br/>Overall, this work sheds light on the advancements in natural polymer-based ink development for additive manufacturing, specifically targeting DLP technology, and emphasizes the potential of integrating photoluminescent fillers to expand the functional capabilities of 3D printed objects. The findings presented in this abstract contribute to the broader understanding of materials development in additive manufacturing.