Abstract Closed-cell photopolymer 3D printing remains out of reach for traditional vat-based Digital Light Processing (DLP) because entrapped resin is challenging or impossible to remove after printing. For parts with internal cavities, this introduces issues such as excess weight, reduced accuracy, and limited functionality in the printed object. This work introduces thin-film DLP, enabling accurate fabrication of hollow internal cavities in resin-printed parts. A thin-film casting approach is employed to eliminate the resin vat, achieving uniform deposition and selective curing of thin resin films layer-by-layer. This approach achieves near-zero resin entrapment (150 wt% with conventional vat-based method). Printing of enclosed cavities as small as 750 μ m in diameter is demonstrated, along with up to a 25-fold variation in stiffness by adjusting internal cavity geometry. Furthermore, by significantly minimizing resin cross-contamination and cleaning complexity, this method streamlines the process of multi-material 3D printing, enabling prints with dissolvable support structures and capacitive sensing capabilities. The thin-film DLP approach facilitates the printing of complex, functionally graded multi-material models with internal cavities, expanding the capabilities of 3D printing for applications such as biomedical devices, soft robotic actuators, and integrated structural electronics.
Sun et al. (Wed,) studied this question.