Fabrication and characterization of laser micromachined hollow microneedles

Three-dimensional arrays of hollow and solid microneedles have been fabricated using laser micromachining techniques. Excimer (UV) and infrared (IR) laser machining was used to create molds for electrodeposition of metals. Mold materials included polyimide (Kapton), polyethylene terephthalate (Mylar), and titanium. IR laser machining was also used to cut solid needle designs directly from stainless steel. The mechanical stability and insertion characteristics of hollow microneedles were tested. The force necessary for insertion was found to vary linearly with the interfacial area of the microneedle. The force necessary for the fracture of a microneedle was found to increase with the tip diameter, wall angle, and wall thickness. Over the range of microneedle geometries tested, the margin of safety between the force for insertion and the force for fracture was the greatest for microneedles with the smallest diameter and the greatest wall thickness.