Designing Smartly: Understanding the Crystallinity of Melt Electrowritten Scaffolds

Melt Electrowriting (MEW) is a powerful technique in tissue engineering, enabling the precise fabrication of scaffolds with complex geometries. One of the most important parameters of MEW is collector speed, which has been extensively studied in relation to critical translation speed. However, its influence on crystallinity was overlooked. Crystallinity is crucial for the mechanical properties and degradation behavior of the scaffolds. Therefore, in this study, we present how printing affects the crystallinity of fibers and the resulting mechanical properties of MEW scaffolds. In systematic analysis, we observed a significant reduction in scaffold crystallinity with increased speed, as evidenced by wide-angle X-ray scattering. This decrease in crystallinity was attributed to differences in cooling rates, impacting the polycaprolactone molecular orientation within the fibers. By using tensile testing, we observed the decrease in scaffold Young's modulus with increasing collector speed. Given the relation between crystallinity and mechanical properties of the material, we developed a finite element analysis model that accounts for changes in crystallinity by employing distinct bulk Young's modulus values to help characterize scaffold mechanical behavior under tensile loading. The model reveals insights into scaffold stiffness variation with different architectural designs. These insights offer valuable guidance for optimizing 3D printing to obtain scaffolds with desired mechanical properties.