A multiphysics predictive framework for cell viability and filament morphology in FRESH bioprinting

Freeform Reversible Embedding of Suspended Hydrogels (FRESH) has garnered growing interest in biofabrication because it enables high shape fidelity and the fabrication of complex architectures. However, the slender nozzles used in FRESH increase the residence time of cells exposed to high shear stresses, elevating the risk of shear-induced injury. Here, we present a multiphysics predictive framework that quantitatively links material properties, extrusion conditions, and a newly developed energy-dose-based cell viability model to predict printed cell viability and filament morphology. The framework showed good agreement with experimental measurements and numerical simulations, supporting its reliability and applicability. Sensitivity analyses were further performed to quantify the contributions of key printing parameters to cell damage. In addition, the mechanisms underlying extruded filament morphology evolution were elucidated, and the printability window was quantitatively characterized. Overall, this work provides an engineering modeling tool to balance shape fidelity and cell viability and to optimize process parameters in FRESH.