Characterization of surface micromachined hollow metallic microneedles

In this paper, metallic microneedles have been characterized for their mechanical and fluid flow properties. The characteristics of various microneedle design features including micromechanical barbs, varying shaft lengths and varying tip taper angles / geometries were studied. The penetration force was found to range from 7.84 gF for a microneedle of shaft length 500 μm, to 9.35 gF for a length of 1500 μm, both with a tip taper angle of 30°. The microneedles with a 15° and 20° linear tip taper penetrated 5% and 25% of the time, respectively. The buckling force was found to be 98.38 gF for a 500 μm long microneedle shaft, 72 gF for a needle of shaft length 1000 μm, and 51.5 gF for a 1500 μm long shaft. The microneedle fluid flow characteristics were also studied. For water, an average pressure of 30.0 KPa was required for a flow rate of 1000 μL/hr and 106.0 KPa for a flow rate of 4000 μL/hr.