Mechanical Properties of Soft Materials in 3D Printing: A Preliminary Quality Assessment

The use of soft materials in 3D printing has become widespread in the biomedical field. It allows the production of patient-specific models, prosthetics, and tools for surgical planning. Among 3D printing methods, PolyJet technology is known for its high resolution and ability to combine materials with different properties. This study looks at how the printing direction (horizontal vs. vertical) affects the mechanical properties of a soft material Agilus30 { }^{\mathrm{TM}}, often used in healthcare. Sixteen samples were printed in both directions and tested following the ISO 527-1A standard. The results show that vertically molded specimens are weaker: They have an ultimate tensile strength of 50 \% less and elongate 36 \% less before breaking than horizontally molded specimens. Specifically, the former showed a tensile strength of 0.36 \pm 0.01 MPa, the latter 0.72 \pm 0.02 \mathrm{MPa}. A practical method was also applied to calculate the elastic modulus by subdividing the stress-strain curve into smaller linear trends. This helps to better understand how the material behaves at different strain levels. Already from the first linear trend, a different Young's modulus was found: 0.52 \pm 0.02 \mathrm{MPa} and 0.62 \pm 0.02 \mathrm{MPa} for the vertical and horizontal specimens, respectively. The results were compared with the material datasheet, confirming that the anisotropy introduced by the printing process cannot be neglected when choosing materials.