An efficient and easily adjustable heating stage for digital light processing set-ups

Digital light processing (DLP) is a versatile additive manufacturing technique able to quickly create complex 3D constructs. DLP has been used successfully for many years in dental applications and rapid prototyping and has gained recent attention in the field of tissue regeneration. Especially the advances in fabricating soft tissue constructs have favored the development of biocompatible and bioresorbable resins. However, to be printable, a resin needs a viscosity of < 10 Pa.s. Thus at ambient temperatures, these resins often require the use of added solvents or reactive diluents (RD) to lower the formulation viscosity to enable printing. Alternatively, the temperature of the resins can also be increased to lower their viscosity. However, most commercial DLP printers come without a thermally controlled bath, and even lack the possibility of adding this functionality without purchasing a new machine. In this work, we report the development of a transparent indium-tin-oxide (ITO) based heating stage that is low-cost and can be easily implemented by other research groups with an existing DLP printer. We then demonstrate that this heating solution ensures a constant, controllable temperature for each layer that is photocured. Furthermore, we showed the effectiveness of this approach by fabricating complex 3D structures using different biocompatible poly(ester) and poly(ester-co-carbonate) urethane acrylate based resins that are unprintable at ambient temperature. The heating stage reported herein represents a small, but impactful improvement that can be applied to any commercial DLP printer, expanding the scope and fidelity of printable resins.