Insertion Force Estimation of Various Microneedle Array-type Structures Fabricated by a Microstereolithography Apparatus

Microneedles have been fabricated for painless drug delivery via skin. These microneedles have limitations on fabricating and drug amount due to their small size. But the continuous growth of MEMS and LIGA technologies enable fabricating more smaller microneedle, and array-type microneedles can deliver more drug to blood vessels via skin. In this case, the strength against human skin has to be considered according to the shape and arrangement of microneedles. In this paper, instead of MEMS and LIGA technologies, a microstereolithography technology was used to fabricate various microneedle array-type structures. A microstereolithography is a noble process for fabricating complex 3D microstructures with a few micrometers resolution. First, we fabricated three array-type microneedles which shapes are likely to be a quadrangular, but has different dimensions. To analyze fracture force of fabricated microneedle array-type structures, an analysis tool was used. In the analysis the microneedle array was modeled as a quadrangular pyramid with different dimensions which are the same as the fabricated structures. The force acting on microneedle array was distributed load over the whole surface contacted on needle base. Also, to optimize the arrangement of microneedle array, we modeled two microneedles which distance is various. From the result of the analysis, optimal shape, arrangement of microneedle array, and stress acting on the microneedle were found