Fabricating high-strength color resin composite via material jetting using ink with added fillers

The mechanical properties of models are crucial in determining the industrial applications of additive manufacturing techniques. Material jetting (MJ) has been primarily limited to mold-making, prototyping, etc., owing to its low strength. Low viscosity and rapid curing, which are essential ink characteristics of MJ, lead to the low strength of MJ models. This study aimed to develop methods to increase the strength of MJ models by adding fillers to the ink. We optimized the shape and size of the filler, modified the surface properties, and optimized the methacrylate monomer formulation of the ink. To develop a colorization process suitable for filler-added inks, we investigated a method to apply transparent ink over small-colored ink droplets. We achieved a bending strength of 180 MPa for colorless models and 177 MPa for colored models, which is remarkable compared to the typical MJ product strength of 90 MPa or less. These findings clarify the design guidelines for high-strength MJ ink, making the direct manufacturing of production parts requiring both esthetic beauty and high strength in colors, such as artificial teeth, dentures, and eyeglass frames, more realistic.