Micromolding methods for hollow microneedle arrays using megasonically enhanced casting

This paper presents novel methods to fill complex micromold inserts for both positive and negative structures, i.e. high-aspect-ratio micropillar and deep slender cavities. Megasonic agitation is applied during polymer casting into the mold inserts. The replication is successfully demonstrated with hollow microneedle arrays. The mold inserts are fabricated using a combination of anisotropic wet etching and deep reactive ion etching (DRIE) of silicon. The mold features to form microchannels either are realized using SU-8 lithography on silicon cavities or apply a two-part insert with silicon comb structures. Needles realized with this method are 250 mum in length with a side-length of 200 mum and comprise channels with cross-sectional areas of 40times40 mum².