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Multilayered polymeric balloon catheters, one of the most important components during interventional treatment, are drawing more attention recently due to the microscale cross section, excellent mechanical properties, and high accuracy. During multilayered polymeric balloon catheter processing, many operating conditions can affect the size and shape of cross sections. In this study, polymer melt flow behavior inside extrusion die is theoretically analyzed first. Then, ethylene vinyl acetate (EVA) and polypropylene (PP) are selected as the build materials to produce the middle and inner layers of three‐layered polymeric balloon catheters, while polyamide (PA) and thermoplastic elastomer (TPE) are used to make the outer layer of two types of catheters, respectively. Based on the material selection, a three‐layered coaxial die is designed and manufactured to coextrude three different polymer melts to form corresponding catheters. In addition, the effects of operating conditions including outer layer materials, pulling speed, gas flow rate, and screw rotation speeds on the diameters and wall thicknesses as well as the concentricity and ovality of the extrudates are investigated. Finally, the PA‐EVA‐PP and TPE‐EVA‐PP three‐layered catheters are successfully fabricated, which have well‐defined geometries and high shape accuracy.

In order to optimize the wall thickness distribution of medical balloon, kyphoplasty balloon was chosen as the research object, the uniformity of wall thickness distribution was taken as the evaluation index, and the influence of stretch blow molding process on the uniformity of kyphoplasty balloon was investigated. In this paper, 16 sets of orthogonal test schemes were studied by selecting four main parameters such as forming temperature, forming pressure, stretching distance, and holding time of stretch blow molding process based on the L16(44) Taguchi method orthogonal table. The statistical analysis showed that the forming temperature was an utmost parameter on the uniformity, while an optimal scheme was obtained and an optimal balloon with the uniformity of 95.86% was formed under the scheme. To further quantify the relationship between the uniformity and the parameters, artificial neural network (ANN) and nonlinear regression (NLR) models were developed to predict the uniformity of the balloon based on orthogonal test results. A feed-forward neural network based on backpropagation (BP) was made up of 4 input neurons, 11 hidden neurons, and one output neuron, an objective function of the NLR model was developed using second-order polynomial, and the BFGS method was used to solve the function. Adequacy of models was tested using hypothesis tests, and their performances were evaluated using the R2 value. Results show that both predictive models can be used for predicting the uniformity of the balloon with a higher reliability. However, the NLR model showed a slightly better performance than the ANN model.

An optimization system of extrusion process parameters was designed to rapidly extrude a microtube with a target diameter and wall thickness for forming medical balloons with personalized size characteristics. Firstly, the double convected pom-pom (DCPP) model was selected for the numerical simulation of the tube extrusion process, and different parameter combinations and their corresponding simulation results were extracted based on orthogonal experiments. Secondly, the nonlinear functional relationships between microtube diameter and wall thickness with extrusion parameters were established based on the response surface model (RSM). Finally, the nondominated sorting genetic algorithm II (NSGA-II) and response surface model (RSM) were mixed to find the optimal parameters of the tube extrusion. The extrusion experiment results, taking three microtubes with different target size characteristics (1, 0.15), (1, 0.2), and (1.5, 0.2) as examples, show that the average error between the actual and predicted values of diameter and wall thickness of three microtubes is 6.53%, where the average diameter error is 7.3%, the wall thickness error is 5.77%, the maximum value is 9%, and the minimum value is only 1.3%.

Multilayered balloon catheters are attracting more attention in recent years. Multilayered balloon catheters have some unique properties such as meso-/microscale dimensions, small wall thickness, and strict requirements of dimensional accuracy. In this study, three-layered polymeric balloon catheters composed of polyamide, ethylene vinyl acetate, and polypropylene (PA/EVA/PP) are successfully fabricated using a three-layered coextrusion die and the polymer melt flowing behavior through the extrusion die are analyzed. Both the diameter and wall thicknesses have been selected as the targeted structural parameters to investigate the effects of pulling speed, air injection volume rate, and screw speed on the quality of the extrudates. The optimal combination of these three operating conditions has been achieved. It is found that pulling speed can significantly affect the diameters of the extruded balloon catheters. The variation interval values of outer profile diameter and inner cavity diameter with the extrusion experiments are 20.95% and 13.04%, respectively. The screw speed of each layer has a great influence on the wall thickness of each layer. Through the influence of outer screw speed, middle screw speed and inner screw speed, the variation interval values for outer layer wall thickness, middle layer wall thickness, and inner layer wall thickness are 31.06%, 35.69%, and 31.35%, respectively. The air injection volume rate has negligible effect.