Analysis and modeling of the contraction phenomenon in the post-processing of bioprinted bone

Given the importance of angiogenesis in osteogenesis, there is increasing demand for bone-grafts that support vascularization, avoid secondary complications, and can be tailored to patient-specific defects. Bioprinted bone has therefore gained attention for treating large defects. However, cells embedded in hydrogels generate traction forces through proliferation and migration, leading to hydrogel contraction and morphological changes; thus, predicting these changes before fabrication is essential. This study models hydrogel morphological alterations, analyzes cellular behaviors affecting the 3D matrix, and examines the role of geometry and mechanical properties using the finite element method in COMSOL Multiphysics 6.2. A phenomenological model governing morphological change is combined with the Kelvin–Voigt viscoelastic model, incorporating the effect of collagen density on cellular traction forces. Computational results confirm gravity-driven heterogeneous cell distribution in the hydrogel’s liquid phase. Findings show that macroscopic cavities and cell concentration patterns strongly influence contraction. Hydrogel geometry significantly affects stress distribution, which may promote cell proliferation, survival, and differentiation or contribute to cellular damage. Results further reveal contraction occurs when the aggregate modulus (Ha) drops below 0.9 kPa. Overall, the proposed computational model clarifies the interplay between cellular activity and hydrogel mechanics, enhancing understanding of mechanical–biological interactions in bioprinting and supporting improved design strategies for bone tissue engineering.