Assessment of geometrical dimensions and puncture feasibility of microneedles manufactured by micromilling

Microneedles are an emerging technology designed to deliver drugs into human tissue. In this work, we assess the microneedle’s manufacturability by employing micromilling with a minimum quantity lubrication (MQL) system. A set of AISI 316L square pyramidal microneedles was fabricated and characterized using dimensional and surface metrology. Needle height (Hn), base length (Lb), tip radius (Rt), and the tip’s angle (θ) were studied. Additionally, surface roughness was quantified to correlate surface topography damage with tool wear (Dr). Experimental data shows tip truncation after manufacturing 30 needles (i.e., a tip radius between ~32 μm and 49 μm for manufacturing 10 and 30 needles, respectively). Additionally, to evaluate the effect of the tip’s morphology on the proficiency of the microneedles for a puncture, a numerical analysis to study the impact of tip truncation length (Tt) on puncture with an in silico assessment using COMSOL Multiphysics was performed. Data and insights from this work suggest that micromilling microneedle arrays is viable, considering the number of needles machined according to the cutting parameters selected to ensure functionality.