Auxetic Structure Inspired Microneedle Arrays for Minimally Invasive Drug Delivery

Microneedle Arrays (MNAs) are promising drug delivery tools aimed at lowering invasiveness and pain. Many design parameters are optimized to lower penetration force in MNAs. An important parameter is the microneedle width as that relates directly to the force required to penetrate the skin, the lower the width the lower the penetration force needed. This research explored the use of auxetic structures known for having negative Poisson ratios in the design of MNAs. As the needles are inserted the compression on the needles causes their radial dimension to shrink instead of increasing as in positive Poisson ration structures. This study has shown a 25% reduction in penetration force due to using an auxetic structure instead of a conventional non-auxetic structure. The research employs additive manufacturing and soft molding to fabricate the MNAs. This study emphasizes the viability of using auxetic structures in MNA design.