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Maskless fabrication of high aspect ratio structures by combination of micromolding and direct drawing

This paper presents a fabrication process combining micromolding and direct drawing, and its application to the development of high aspect ratio microneedles. Without using photolithography or etching, the proposed process creates microneedles with: 1) higher aspect ratios than that of the original mold, 2) controllable needle diameter for optimized mechanical strength, and 3) arrowhead-shaped tips for potentially increased capacity and effective payload delivery. The needles presented are formed with biocompatible, water-soluble polymers, but the fabrication process inherently allows many kinds of polymers to be exploited. Various high aspect ratio 3D structures were fabricated and characterized, and the fabrication result was compared with theoretical prediction. Water-soluble microneedle arrays have been fabricated and successfully penetrated into porcine skin, fully releasing the drug-surrogate into the dermis layer within a minute.