Additive Manufacturing to Mimic the Nonlinear Mechanical Behavior of Cardiac Soft Tissue.

Soft biological tissues display highly nonlinear and anisotropic mechanical behavior, which is critical to their physiological function. Replicating these mechanical properties using engineered materials and additive manufacturing represents a significant challenge in biomedical engineering, particularly for surgical simulation, device development, and preclinical testing. The left atrial appendage (LAA) was selected since it plays a central role in thrombus formation during atrial fibrillation, significantly contributing to cardioembolic stroke. This study proposes a framework for reproducing the nonlinear stress-strain behavior of soft tissue using 3D-printed models. The methodology integrates experimental material selection with optimization of key printing parameters to ensure structural reliability and functional mechanical performance. Two polymers-polyurethane (TPU) and a thermoplastic with elastomer-type behavior (TPE)-were selected for their tunable hardness and elasticity. A parametric study was conducted to investigate the effects of Shore A hardness (60A to 100A), infill density (0% to 100%), and external shell number (zero to two) on the tensile performance of printed models. Mechanical testing was performed to extract stress-strain curves and evaluate the mechanical response. The practical implications of this study are significant, demonstrating the potential of additive manufacturing for anatomical reproduction and replicating functional mechanical properties in soft tissue models.