3D-Printed multi-material liver model with simultaneous mechanical and radiological tissue-mimicking features for improved realism

Abstract

Anatomic models have an important role in the medical domain. However, soft tissue mechanical properties’ representation is limited in mass-produced and 3D-printed models. In this study, a multi-material 3D printer was used to print a human liver model featuring tuned mechanical and radiological properties, with the goal of comparing the printed model with its printing material and real liver tissue. The main target was mechanical realism, while radiological similarity was a secondary objective. Materials and internal structure were selected such that the printed model would resemble liver tissue in terms of tensile properties. The model was printed at 33% scaling and 40% gyroid infill with a soft silicone rubber, and silicone oil as a filler fluid. After printing, the liver model underwent CT scanning. Since the shape of the liver is incompatible with tensile testing, tensile testing specimens were also printed. Three replicates were printed with the same internal structure as the liver model and three more out of silicone rubber with 100% rectilinear infill to allow a comparison. All specimens were tested in a four-step cyclic loading test protocol to compare elastic moduli and dissipated energy ratios. The fluid-filled and full-silicone specimens had initial elastic moduli of 0.26 MPa and 0.37 MPa, respectively, and featured dissipated energy ratios of 0.140, 0.167, 0.183, and 0.118, 0.093, 0.081, respectively, in the second, third, and fourth loading cycles. The liver model showed 225 ± 30 Hounsfield units (HU) in CT, which is closer to real human liver (70 ± 30 HU) than the printing silicone (340 ± 50 HU). Results suggest that the liver model became more realistic in terms of mechanical and radiological properties with the proposed printing approach as opposed to printing only with silicone rubber. Thus, it has been demonstrated that this printing method enables new customization opportunities in the field of anatomic models.