Puncturing soft substrates with microneedle Arrays: Experiments, simulations, and machine learning predictions

Microneedle arrays are innovative medical devices used for drug delivery, tissue adhesion, and neural signal detection. Understanding how their geometric features influence puncture performance in soft substrates is crucial for optimal design. This study first investigates the effects of shaft diameter and tip angle of a single microneedle through puncture experiments, revealing that reducing these parameters decreases the critical puncture force and depth. Subsequently, the puncture of three types of microneedle arrays: planar, "arrow-shaped", and "wave-shaped", are investigated via experiments and simulations. Key geometric factors, including height difference, spacing, tip angle, and diameter of microneedles within each microneedle array, are analyzed for their impact on the peak puncture force and the puncture efficiency. Results indicate that the height variation significantly affects the peak puncture force of "wave-shaped" arrays, while increased spacing enhances the puncture efficiency and the peak puncture force across all designs. Though larger tip angles reduce the puncture efficiency, this effect is mitigated in "array-shaped" and "wave-shaped" arrays. Smaller diameters lower the peak puncture force and improve the puncture efficiency in all cases. Furthermore, 152 simulation results are utilized to train an artificial neural network (ANN), which successfully predicts the puncture force at a specified depth for a microneedle array when the geometric parameters of the array are provided. This study provides insights into the combined effects of microneedle array geometries on puncture performance, guiding the design of more effective microneedle systems.