Abstract:

Objective This study aims to comprehensively investigate the performance degradation mechanism of poly-4-methyl-1-pentene (PMP) membrane fabrics used for extracorporeal membrane oxygenation (ECMO) affected by the warp-knitting preparation process. The primary focus is to elucidate the influence of yarn tension, a critical process parameter, on the morphological evolution, pore structure stability, and ultimate gas exchange performance of the PMP membrane. The research seeks to establish a quantitative relationship between process mechanics and material functionality, thereby providing a theoretical foundation and practical guidelines for the optimized design and low-damage industrial production of high-performance ECMO membrane fabrics.

Method An integrated methodology combining geometric modeling, finite element (FE) simulation validated by experimental results, and an extended numerical study was employed. Initially, a three-dimensional geometric model of the ECMO membrane fabric stitch was constructed based on actual dimensional measurements (with stitch height being 593.15 μm, stitch width 243.25 μm) obtained from fabrics knitted on a TM-WEFT warp-knitting machine. This model, developed using the proprietary textile CAD software Textile AI Design System iTDS 3.0, accurately represented the interaction between the polyester yarn and the PMP membrane. Subsequently, a mechanical FE model was established in Abaqus CAE-2021. The material parameters for the PMP membrane (Young's modulus 147.0 MPa, yield strength 2.28 MPa) and polyester yarn were determined through uniaxial tensile tests and incorporated into the simulation. The model was rigorously validated against experimental data, including scanning electron microscopy (SEM) for morphological changes and porosity analysis for quantifying open porosity (OP) and closed pore volume under different tension levels. The established model was used to simulate the knitting process by applying varying yarn tensions ranging from 0.1 N to 0.45 N at the yarn end, with fixed constraints at other key points. The mesh configuration was meticulously designed, employing tetrahedral elements with local inflation techniques for contact regions post-knitting, resulting in models with up to 2.83 million elements and a mesh quality consistently above 0.83. The simulation outputs, namely Logarithmic Strain (LE) and Equivalent Plastic Strain (PE), were analyzed to assess total and irreversible deformations.

Results The numerical study revealed that yarn tension applied in knitting significantly affects the deformation and gas exchange performance of PMP membranes. When the yarn tension was below 0.15 N, the PMP membrane showed elastic deformation with minimal impact on its structure and performance. As the tension increased to 0.20 N, the membrane began to exhibit plastic deformation, resulting in a reduction of the outer diameter and pore structure deformation. When the yarn tension applied in knitting exceeded 0.20 N, the plastic deformation became pronounced, leading to a significant decrease in open porosity. Specifically, at a tension of 0.35 N, the open porosity decreased by 15.6%, and the closed pore and pore-wall volume ratio increased by 21.6% compared to the initial PMP status. SEM images confirmed that high tension caused irreversible damage to the pore structure, including pore collapse and the formation of wrinkles and microcracks. Both simulation and experimental results demonstrated that excessive yarn tension adversely affects the gas exchange capacity of the membrane.

Conclusion This study successfully deciphers the damage mechanism inflicted upon PMP membrane fabrics during the ECMO warp-knitting process, establishing yarn tension as the pivotal controlling parameter. The research conclusively identifies 0.20 N as the critical threshold beyond which significant plastic deformation occurs, leading to irreversible pore structure collapse and a consequent severe decline in gas exchange efficiency. The synergistic application of FE simulation and experimentation has not only validated the "deformation-diffusion path" physical model but also provided quantitative criteria for process optimization. Therefore, strictly controlling the yarn tension below 0.20 N is imperative for minimizing mechanical damage, preserving optimal porosity, and ensuring the high gas exchange performance of ECMO membrane fabrics. These insights offer robust theoretical support and actionable, quantitative guidance for the precision manufacturing and industrial-scale production of reliable, high-performance ECMO membrane fabrics, advancing the endeavor toward their domestic production and material optimization.

Key words: extracorporeal membrane oxygenation, PMP membrane fabric, oxygenator membrane fabric, medical textiles, yarn tension, gas exchange performance, finite element simulation