Objective:To conduct theoretical analysis and experimental research on peripherally inserted venous catheters, establish theoretical models of interaction between different materials catheters and simulated skin tissues, and test different catheters at the same time to provide theoretical basis and experimental basis for the optimization design.Methods:According to the mechanical properties of the catheter at 25 ℃ and 37 ℃, a finite element model of the catheter and simulate skin tissue was established. The relationship between catheter folds and material and structure during puncture was analyzed, and the stiffness, radiographic properties, etc. were tested experimentally.Results:The performance of the catheter at different temperatures is closely related to its material. The wrinkle situation of the catheter is related to the catheter material and the inclination of the wedge surface. The elastic modulus of the polyurethane (PU) catheter is about 500 MPa and 250 MPa, respectively at room temperature (25 ℃) and body temperature (37 ℃), which meets the clinical needs of high rigidity during puncture and soft material during indwelling. When the catheter structure is the same, the PU catheter is less prone to wrinkles than the fluorinated ethylene propylene copolymer (FEP) catheter. When the catheter material is the same, the smaller the inclination of the wedge surface, the less likely the catheter to wrinkle.Conclusions:Appropriately reducing the inclination of the wedge-shaped surface of the needle of peripherally inserted venous catheters can improve the success rate of puncture. The PU catheters have good mechanical properties, they are not prone to wrinkles during puncture, and their stiffness can be reduced at body temperature, which can not only increase the success rate of puncture, but also reduce the occurrence of complications. Therefore, PU catheters have a better clinical application prospect.

Objective To compare and analyze the relationship between geometric parameters of the needle of different insulin pens and their puncture force, flow rate, and pressing force. Methods The human skin tissue model and needle model were established, and the finite element simulation analysis of needle puncture was performed. Using a test platform, 25 kinds of needles with different geometric parameters were tested for the puncture force, pushing pressure, flow rate and other parameters. The influence of geometric parameters on the performance of the needles were analyzed. Results The puncture force of the needle was closely related to its section design. Compared with the three-section needle, the five-section needle increases the secondary inclination angle and the condyle angle, increases the contact area between the needle and the tissue, and make the change of the contact angle more smoothly, which reduce the needle penetration force. The smaller the outer diameter of the needle, the smaller the penetrating power. The larger the inner diameter of the needle, the greater the fluid flow rate, the smaller the pushing pressure, and the higher the injection accuracy. Conclusions Five-section, ultra-thin-walled or ultra-thin-walled needles have more excellent performance. On the basis of ensuring the strength of the needle, the needle's geometry can be optimized to reduce the puncture force. The results of this study can provide theoretical basis and experimental basis for the design of needles for insulin pens.