Optimizing CNC milling parameters for manufacturing of ultra-sharp tip microneedle with various tip angles

Microneedle technology has emerged as an advanced method for transdermal drug delivery, which focuses on diverse fabrication techniques to develop microneedles with various models and geometries. This study explores the application of Computer Numerical Control (CNC) milling technology to create microneedle master molds with extremely sharp tips. We examined the effects of two key machining parameters, feed rate and ramp angle, on the tip sharpness of the microneedles. Our results showed that increasing both the feed rate and ramp angle could significantly reduce machining time. However, a higher feed rate also led to larger tip diameters and notable tip defects. Conversely, changes in the ramp angle at a constant feed rate had minimal impact on tip size. We identified an optimal condition balancing cutting time and tip sharpness at a feed rate of 100 mm/min and a ramp angle of 1.5°. Additionally, we assessed the CNC's capability to produce needles with different tip angles. The findings confirm that needles with varying tip angles maintained tip diameters below 10 μm, with needles having a 50° tip angle exhibiting the sharpest tips at approximately 3.3 μm. Further compression, insertion and diffusion tests were conducted to evaluate the performance of needles with different geometries.