Model construction and knitting damage mechanism of extracorporeal membrane oxygenation membrane fabric

Extracorporeal Membrane Oxygenation (ECMO) relies critically on the gas exchange performance of poly-4-methyl-1-pentene (PMP) membrane fabrics, which can be significantly affected by mechanical damage during the knitting process. However, the damage mechanisms induced by yarn tension during membrane fabric formation remain insufficiently understood. In this study, a combined geometrical modeling, finite element simulation, and experimental approach was employed to systematically investigate the mechanical deformation and functional degradation of PMP membranes during warp-knitting. A three-dimensional stitch geometry model of ECMO membrane fabrics was constructed and integrated into a finite element framework to simulate yarn tightening and contact-induced compression under different yarn tensions. The simulation results revealed a distinct elastic–plastic transition in the PMP membrane when yarn tension exceeded approximately 0.2 N, characterized by pronounced logarithmic and equivalent plastic strain localization. Experimental validation through outer diameter measurements, cross-sectional SEM observation, and porosity analysis demonstrated strong agreement with the simulation predictions. Below 0.2 N, membrane deformation was predominantly elastic and reversible, whereas higher tensions led to irreversible plastic flow, lumen collapse, wall folding, and pore closure. Quantitative pore structure analysis showed that exceeding the critical tension resulted in a significant reduction in open porosity and a marked increase in closed pore and wall volume fraction, directly impairing gas exchange capability. These results collectively establish 0.2 N as a critical yarn tension threshold for maintaining the structural integrity and functional performance of PMP-based ECMO membrane fabrics. This work elucidates the knitting-induced damage mechanism of ECMO membrane fabrics and provides a quantitative theoretical basis for tension control and low-damage manufacturing in large-scale industrial production.