Abstract
A hollow polymer microneedle array with tips and lumens that mimic conventional hypodermic needles, fabricated using UV lithography, and a single-step micromolding technique, is presented for drug delivery into skin. This 6 × 6 needle array consists of 1-mm tall high-aspect ratio hollow microneedles with sharp beveled tips and 150-μm diameter side-opened lumens. A 2-D lithographic mask pattern and the topography of the micromold are utilized simultaneously to define the geometry of the beveled tip and the position of the lumen. Mechanical insertion and fluidic injection characterization of these hypodermic-needle-like (HNL) microneedles (MNs) were performed using excised porcine skin as a substrate. The required insertion force of an HNL MN is 0.275 N, which is comparable with that of a 26-gauge hypodermic needle, 0.284 N. These results are an order of magnitude reduction in insertion force over pyramidal-tip MNs of comparable diameter previously reported by us. This insertion force reduction confirms that the tip geometry is an important factor in utilization of MNs in these applications. No needle fracture was observed under an optical microscope following the pressing of an HNL MN against excised porcine skin with application force of 50 N. Preliminary manual injection of dye through an HNL MN from a syringe into excised porcine skin verified the injection functionality of HNL MNs. [2013-0219].
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