# Artificial Heart Valve Scaffold Based on Electrospun PCL/PU Three-Layer Composite Fibers
## 2 Experimental Section
### Modeling and Simulation of the Composite Heart Valve  
Figure 1 shows the main experimental processes of electrospun composite fiber heart valve scaffold. Specifically, SOLIDWORKS2021 (Version number: SP2.0) software was used to create a simple heart valve model. The model was 2.45 cm in height, 2.306 cm in outer diameter, and 1.76 cm in inner diameter, which best mimicked the natural heart valve [18]. Based on the modeling files, an aluminum alloy mold for an electrospun heart valve was fabricated using 3D printing technology. Figure 2a exhibits its 3D schematic diagram and three-view drawing.  
Figure 1: (**a**) SOLIDWORKS software was used to establish heart valve model. (**b**) Fabrication of heart valve metal mold by 3D printing. (**c**) COMSOL software was used to simulate electric field distribution on pretreated surface of heart valve mold. (**d**) Electrospinning polymer fiber layers on mold. (**e**) Electrospun heart valve scaffold stripped from mold. (**f**) Human valve interstitial cells were cultured on scaffold. (**g**) Cell adhesion was observed by confocal fluorescence microscopy.  
An EOS M290 powder bed fused 3D printer was used to make the aluminum molds. The printer has a molding space of 250 \(\times\) 250 \(\times\) 325 mm and is equipped with a 400 W laser. The specific printing process is as follows:  
Solidworks software was used to design the 3D model of the heart valve mold and convert it into STL format files. After importing the STL file into the printer control system, the printing parameters were adjusted as follows: layer thickness 0.1 mm, temperature 600 \({}^{\circ}\)C, scanning speed 1000 mm/s. After setting, the aluminum powder and the binder are mixed and evenly spread on the printer workbench. The 400 W laser then selectively melts the powder according to the model data and gradually piles up into metal parts. After printing, we waited for the material to cool. Then the finished product was taken out for grinding and polishing to obtain the electrospun heart valve mold we needed.  
The artificial heart valves were prepared by electrospinning; fibers were deposited on the aluminum alloy mold (Figure 1b). Due to the irregular charge distribution across the conductor, fibers deposited unevenly [19]. To solve this problem, COMSOL6.2 software was used to simulate the electric field distribution on the surface of the mold during the experiment. As illustrated in Figure 2b, variations in the conductor's surface curvature correspond to differences in electric field strength. Regions with greater curvature attract more electrospun fibers, whereas areas with lesser curvature attract fewer fibers. To ensure uniform fiber layering and that the mechanical integrity of the electrospun fiber film meets required standards, pretreatment of the mold before electrospinning is necessary. Methyl silicone oil (99%, Hope INTERNATIONAL TRADING Co., Ltd., Qingdao, China), which known for its exceptional chemical stability, lubricity, and insulating properties, was applied to coat the mold's outer edges and sharp points [20]. Methyl silicone oil remains inert with the valve material used in this experiment. Its high lubricity facilitates later demolding of samples. As an insulator, methyl silicone oil forms bound charges in the  
Figure 2: (**a**) Three views and 3D schematic diagram of mold design of artificial heart valve. (**b**) COMSOL simulation of electric field distribution on surface of heart valve mold (V m\({}^{-1}\)).  
electric field, generating an auxiliary field that offsets part of the external field, thereby dispersing the electric field lines on the surface to promote uniform fiber deposition.