Injection molding simulations for the manufacturing of polymer hollow microneedles

Abstract

Abstract. Polymer hollow microneedles (HMNs) offer significant potential in medical, diagnostic, and cosmetic applications due to their minimally invasive nature and high replication capability. However, their fabrication using injection molding with ultrashort pulsed laser ablated molds presents several challenges, particularly in predicting process outcomes such as cavity filling and replication fidelity. This study investigates the role of injection molding simulations in addressing these challenges, focusing on the influence of the venting boundary conditions. Moldex 3D 2023 and 2024 versions are compared with and without the inclusion of venting boundary conditions, showing the importance of venting for the prediction of HMN heights. The 2023 version underestimates the filling height by 45%, while the 2024 version overestimates it by 18%. Furthermore, manual air volume calculations using the ideal gas law revealed deviations in both versions: the 2023 version significantly overestimates the entrapped air volume, while the 2024 version underestimates it. These findings indicate the necessity for more accurate algorithms to model compressible air dynamics in micro-scale geometries effectively. By addressing these challenges and improving the predictive accuracy of injection molding simulations, further research can pave the way for reducing trial-and-error in process development, lowering manufacturing costs, and enabling scalable production of HMNs.