Low-damage preparation of extracorporeal membrane oxygenation warp knit membrane fabrics with adaptive tension
Objective Extracorporeal membrane oxygenation(ECMO)is used to provide continuous extracorporeal blood oxygenation to patients with severe cardiopulmonary failure to maintain the patients'life.The ECMO device consists of an oxygenator,a centrifugal pump,and a control system,of which the oxygenator is the core component for accomplishing the blood oxygenation.This study addresses the problem of technological gaps in the preparation of separation membrane fabrics for oxygenators and presents a study on the low-damage preparation of ECMO membrane fabrics based on warp knitting technology.Method Through the stitch analysis of membrane fabrics made from polymethylpentene(PMP)hollow fibers membrane,the parameters such as knitting stitch,yarn type and other fabric specifications of membrane fabrics were determined.The knit fabrics were manufactured on the special Tricot warp knitting machine from PMP hollow fiber membrane.Based on the experimental results and the understanding of the knitting equipment,warp yarn tension was identified as one of the main influencing factors affecting the damage of the PMP hollow fiber knitting.An adaptive warp yarn tension control method was proposed with the Tricot warp knitting machine through the PID control strategy design and the fifth degree polynomial curve planning,aiming to achieve low-damage knitting of PMP hollow fiber.Results The results showed that the damage of prepared ECMO membrane fabrics was mainly caused by the mismatch of yarn demand between the warp feed and knitting action at constant speed.The knitting tension amplitudes at 900,1 000,and 1 100 mm/rack warp feed were 28,23,and 19 cN,respectively,which led to the attenuation of PMP hollow fiber strength,outer diameter,and air flux.The ECMO membrane fabrics were prepared using the adaptive tension control method.The warp tension amplitude in a single cycle was regulated from 2.4-23 cN to 3-10 cN at the warp feed of 1 000 mm/rack,and the tension fluctuation amplitude was reduced by 56.5%.The results of ECMO film fabric preparation under adaptive tension control showed 3%loss of outer diameter and a 5%loss of strength at the weaving position.The N2 flux was decayed by 17%,CO2 flux by 12%and O2flux by 14%before and after braiding.Compared with the experiment without adaptive tension control,each gas flux index showed 65%enhancement of N2 flux,63%enhancement of CO2 flux,and 62%enhancement of O2 flux,which further exemplified the effectiveness of the adaptive tension control scheme for the low-damage preparation of ECMO membrane fabrics.Conclusion In this paper,based on warp knitting technology,a self-adaptive warp tension regulation method was developed to realize the low damage preparation of ECMO warp-knitted membrane fabrics by using homemade PMP hollow fibers as the substrate.The main research conclusions are as follows.1)Through the membrane fabric preparation experiments,an adaptive tension control method is proposed,and through the PID control strategy and the fifth polynomial speed planning curve,the"peak shaving and valley filling"of the warp yarn tension curve in the preparation process of ECMO membrane fabrics is accomplished,realizing the low-damage preparation of ECMO membrane fabrics.2)The strength,outer diameter,and air flux of the PMP hollow fiber are significantly attenuated during the knitting process of the ECMO membrane fabric on a HKS Tricot warp knitting machine.This attenuation is primarily attributable to the material properties of the PMP membrane.A key contributing factor is the mismatch between the constant speed let-off rate and the actual amount of yarn required for the knitting process.3)By testing ECMO membrane fabrics preparation under adaptive tension control,it was found that the mechanical properties,outer diameter,and air permeability of the PMP hollow fibers were significantly improved.The N2 flux of the prepared ECMO membrane fabrics was attenuated by 17%,the CO2 flux was attenuated by 12%,and the O2 flux was attenuated by 14%.The flatness,density,and gas flux results of the fabric have reached the level of foreign products.
medical textilesoxygenation membrane fabric for extracorporeal membrane oxygenation systempolymethylpentene hollow fiber membranewarp knitted fabriclow-damage preparation methodbreathable property
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