A novel fabrication method of a microneedle array using inclined deep x-ray exposure

We investigated a novel fabrication method of a microneedle array. In microneedle fabrication methods employed to date, researchers have used conventional silicon-based fabrication methods such as inductively coupled plasma etching and wet etching techniques. However, these processes are not sufficient for the fabrication of a longer needle shank and applications such as blood extraction from the skin surface. Using a deep x-ray, high-aspect-ratio (HAR) 3D microstructures can be fabricated. The fabrication process consists of a vertical deep x-ray exposure and a successive inclined deep x-ray exposure. The first vertical exposure makes a triangular column array with a needle conduit through a deep x-ray mask having a triangular and hollow circle shape pattern. The column array is shaped into the microneedle array by the second inclined exposure without additional mask alignment. Changing the inclined angle and the gap between the mask and polymethylmet-acrylate (positive photoresist) substrate, different types of microneedle arrays are fabricated. The fabricated microneedle fulfills the structural requirements for painless drug delivery and blood extraction including a 3D sharp tapered tip, HAR shanks, small invasive surface area and an out-of-plane-type structure. In a skin puncture test, the microneedle array penetrates the skin of the back of the hand without tip breaking.