Advancing a real-time image-based jet lag tracking methodology for optimizing print parameters and assessing melt electrowritten fiber quality

Abstract

Melt electrowriting (MEW) has emerged as an important additive manufacturing process to fabricate high-resolution microscale fibrous scaffolds for engineered tissue applications. However, the complex interplay between the numerous process variables renders parametric optimization of this additive manufacturing technique a challenging task. In order to facilitate the optimization of MEW-jetted fiber fabrication, this study adopts a real-time jet lag tracking methodology. Specifically, this methodology is implemented to determine the optimum conditions to improve the fiber quality featured by a prescribed mean diameter and an enhanced uniformity. Firstly, a serpentine toolpath is designed, and the real-time jet lag length signal is recorded, exhibiting multiple successive peaks. The coefficient of variance CV pv correlated with these peak values is first identified as an indicator of the jet lag stability. Second, for a given pressure ( P ) and translational stage speed ( v ), as the applied voltage ( U ) increases, CV pv is found to initially decrease before reaching a minimum point at U = U c , followed by an increase at higher U values. U c represents an inflection point on the graph of CV pv as a function of U , whereby fiber pulsing is observed when U < U c . Otherwise, an enhanced fiber uniformity is achieved at the expense of detectable current leakage when U > U c . Moreover, at a given P , as v decreases, U c deceases and plateaus at a value U b . Furthermore, U b is found to increase as P increases. These aforementioned dependencies are closely related to the mass equilibrium around the Taylor cone. Finally, based on these results, a systematic protocol is advanced to determine the appropriate P - U - v settings that enable an enhanced printed fiber quality.