High Strength, Polymer Microneedles For Transdermal Drug Delivery

A fabrication technique was reported earlier [1] to produce high aspect ratio hollow circular cross-sectioned microneedles involving just one lithography step. However, the strength of those needles was still not tested. Here, the average failure force for each microneedle was measured experimentally. The insertion force in agar gel, which serves as a reliable human skin equivalent in terms of its visco-elastic properties [2], was obtained. The safety factor, ratio of failure force to insertion force was computed to be almost 600. Therefore, the fabricated microneedles are sufficiently strong to be inserted into the stratum corneum. Further to this, the fabrication process was enhanced to incorporate sharpening of the tips of the microneedles as well as mounting them on a platform such that the bores of the needles are continuous through the bore of the platform on which they are mounted. The process of realizing the platform in the same material as that of the needles makes the assembly less complex and more efficient. (C) 2011 Published by Elsevier Ltd.