Investigation of jet initiation in in-gel near-field electrospinning

In-Gel Near-Field Electrospinning (IG-NFES) integrates near-field electrospinning with embedded three-dimensional printing to achieve high-resolution fiber fabrication within a support gel matrix. We present a multiphysics simulation framework to study jet initiation in IG-NFES. Our framework explicitly incorporates gel drag effects and provides systematic parametric analysis quantifying how material property ratios govern jet stability, enabling predictive material selection and process optimization beyond trial-and-error approaches. We systematically investigated the influence of viscosity, density, and dielectric permittivity ratio on the jet initiation behaviors. Our results reveal that viscosity ratio (M) and dielectric permittivity ratio (Q) are the most critical parameters affecting jet formation and stability. A viscosity ratio of 2.5 promotes stable jet elongation, while significantly lower or higher values lead to premature breakup or jet suppression. As Q increases from 3 to 15, jet behavior transitions from no initiation, to droplet breakup, and finally to stable jet formation due to enhanced electric field focusing on the ink. We also analyzed the roles of two key dimensionless numbers: the electric capillary number (CaE) and the Weber number (We). The transition from droplet formation to continuous jetting is governed by CaE, with stable fiber formation observed within the range of 6–12. Similarly, stable jetting occurs when We lies between 10−5 and 10−3. The model predictions were validated with experiments, confirming the identified regime transitions. These findings offer quantitative insights for optimizing material selection and process parameters in IG-NFES, paving the way for advanced applications in robotics, soft electronics, and biomedical devices.